I need to replace my 904

[secondChanceFury]

Hello, My 904 is puking trans fluid out of the front of the bell housing.

I am looking to take this opportunity to add overdrive to my 69 Fury.

I know i can get at least one 518 from a local yard, and they have a 90 warranty for about 300.
They only have the one 518, but lots of newer electrical versions. I would like to stay with the 518 as it should be plug in play. I know I will need to get my driveshaft adjusted.

I would like to get this confidently back on the road as soon as possible.
If I go with 518 from the yard and it is bad, I really only have REs to choose from which means I have to get a controller to run it. This puts me back up around a 1000+.

I did find a 518 with a warranty from SWEngines for about 1200.
Has anyone from here ever purchased a transmission from this site?

Not sure how they test transmissions, I feel like they are just dismantlers and I may be paying them 1000.00 just to pull it for me.
If the warranty is legitimate It may be worth the piece of mind.

I am having a hard time deciding which way to go.
I have a max of 1500 to spend but of course would love save what I can.
The car is just a cruiser with a stock 318.

What would you do if you were me?

 

[413]

Is the trans still in the car with fluid in it? Does the fluid look ok or burnt up? Is the car decent or beat to death?
Is it wrecked on one corner? Was it just parked and weathered From sitting?

Do you enjoy swapping the trans yourself? Then buy the junkyard trans and converter and try it. Change the fluid and filter and look inside first though. Pressure wash and degrease the trans area on your car first so you are working with clean parts.

If swapping is not that fun for you then get a price on a rebuild from a local good trans shop. If the numbers add up for you then go buy the junkyard trans and converter and take it there.

the weather should be good for doing this job right now. Just remember that the second time of removing the trans goes much quicker.

 

[secondChanceFury]

Thank you for the tips for analyzing junk yard candidates.

I have no issues with pulling the trans multiple times. I have pretty much resigned myself to that fate and accepted it.

It is my understanding that the RH and REs are the same length, so I should only have to adjust my drive shaft once. If that is true, there is no harm in trying the 518 first, maybe it works out. If not, I did find this controller which looks like it would work and there are lots of REs to choose from. The yard said, they really do not care, just keep bringing it back and exchange it within 90 days if it doesn't work. Who knows, maybe I will get lucky.

E-Trans Controller
E-Trans Control

 

[1970FuryConv]

518 is small block trans. 727 big block has different bolt pattern to install at rear of engine block. If you plan to upgrade to a big block, I'd get the 904 rebuilt and save the money for the big block conversion. I had 318/904 in my 1970 Fury convertible. Weak performance. Cost a lot, but I am very glad I changed over to 440/727.

 

[CBODY67]

Years ago, like in a 1968 HOT ROD article on beefing a stock 904 with better frictions and such, it mentioned that UNLESS you needed the additional torque capacity of a 727, to use a beefed 904 as it would take less power to run it, meaning more horses to the rear wheels and better dragstrip performance, as a result. Something NOT thought about back then.

Rather than get all excited about some mechanical work, check to see if the fluid is coming from the front converter lip seal. An easy fix! Might need a new converter due to the groove the seal can wear into the converter snout.

Seems like that due to the OD section in the 518, you might have some "re-configuring with a hammer" to the floorpan to clear that OD-section hump, at least on B-bodies, from a magazine article from back then.

Also, an OD with a 2.7 rear axle ratio and carburetion might not be advisable, due to cruise rpms being much lower. Just an observation. No need to add OD to a "down-hill" rear axle ratio. There was a reason that the old 3-spd OD manuals only came with 3.70 rear axle ratios in the first place.

If the trans in your car is on its last legs, find a good trans shop to rebuild it. A stock-spec rebuild with their choice of better frictions (which they might normally do anyway). But in the meantime, that front seal replacement might be all it really needs to fix the leak.

In many cases, relying upon a salvage yard transmission might get you about what you already have, in total durability and such, even if it might be "a good one". Not always good fiscal sense.

Just some thoughts,
CBODY67

 

[MONC440]

I agree with CBODY67. If you are not changing the rear axle gear when the trans hits OD the 318 will struggle and you will find yourself shifting out of OD often and that isn't good on the trans.

You do understand that you will need some fab work on the rear trans mount to make the OD fit. You will probably also have the make some clearance in the tunnel. One suggestion is cut off all the extra ears on the OD trans as they will get in the way.

I have done 518 swap and 47RE swap on B and C bodies and it is easier on the C but not without it's work.

Other things to consider is how you are going to control the OD and torque converter lock up(if used). It is easy on the 518 as you can do this with a toggle switch, with the RE trans you will need a controller as the governor pressure is electronically controlled. On the 518, if you use a toggle switch make sure you step down the voltage to 5 or 6 volts as the solenoids will not last long using straight 12 volts.

If you decide to go with the OD I can answer almost any question you have on this. A good resource for any Mopar trans questions is Cope Racing Transmissions or CRT. John Cope has forgot more about Mopar trans than most of us will ever know and he has a bunch of youtube videos and he talks about 518 swaps.

One more thought if you use a OD trans and later want to go to a big block you can still use the trans by using a Ultabell bellhousing adapter. I have also done this and it worked great.

Here is a pic of the rear cross mount for the 47RE in my 70 Fury.

 

[Triple Pickle]

I myself would have the 904 rebuilt and be confident that my work was not done in vain. The heck with a bunch of junkyard transmissions that, like a cheap crescent wrench, might slip anytime. Just my 2 cents.

 

[CBODY67]

If the converter clutch on the 518s are like the 904-family transmission in my '80 Newport 360 2bbl, it works off of spring pressure vs. fluid pressure, which can be tailored to your needs and rear axle ratio. The earlier (as in '76) TFs had the lockup at 27mph, which was like putting a manual trans in "high" and driving in that gear until you needed a downshift. My '80 Newport hits lockup at about 56mph, above an rpm level which would lug the engine and at a speed range from which there is enough engine power to not need a downshift for normal highway driving. That covers the torque converter lockup, as I know and have experienced it. Still, when the converter gets worn, it can shudder when it locks up and a load is present (as in acceleration or going up a hill). Only way to stop the shudder is to back out of the throttle (removing the load) or use enough throttle to downshift and get past that lockup speed/load situation so a smooth lockup can occur. NOT to forget that the converter and transmission input shafts are hardened, otherwise the converter splines can wear and cause "spin-out" where the converter splines are worn-down too much. Been there, twice.

The OD is electric, so a toggle switch can do that. Unless you get the vac harness and electrical items from a late '80s Chevy pickup truck. They used vac-operated switches to control the electrical lock-up for cruise and unlock for deceleration, and then re-lock for cruise conditions. Getting them at the right value for your vehicle might take some time, so the transmission stays locked-up for best results. An example: Initial lockup at vac above 12" Hg in 3rd or OD, unlock at 8" Hg, then re-lockup at 12"Hg; unlock above 18" Hg for coast-down. But GM also used a valve body switch so that some transmissions would lock-up in 2nd gear, which could be deactivated by somebody who knew what to disconnect. Just a suggestion of how to make things more automatic rather than use a toggle switch. Might be more trouble than it's worth?

KEY thing is all of this is that when going to a more modern automatic transmission, it is not just a bolt-in situation, although it was later a factory option. Past the installation part, the unit must be adapted to other things for your vehicle too. Whether analog or electronic. Which makes getting your existing transmission fixed or rebuilt the best fiscal option for a quick and less expensive situation, plus fewer "teething issues" of getting all of the adaptations done correctly. Even going to a later model 904-family transmission can have its adaptation issues due to the lock-up torque converter timing.

Just some thoughts,
CBODY67

 

[secondChanceFury]

I really appreciate all the feedback.

It seems there is a real case for saving the 904.
I did call my local highly recommended shop about rebuilding the 904 and they said 1500.00.
Which is why I felt if I was going spend that kind of money I could get an upgrade for the same price.

If I go for the RE version, which is likely just because of availability, I was considering using the following controller which seems like it could allow me to set my shift points and lockup.
Has any one had experience with this controller?
E-Trans Controller: E-Trans Control

For me, the OD is really only for freeway driving. I rarely get over 50 around town where this car will spend most of it time.
If I am able to set the lock up close to 60 like CBODY67, does that solve the rear axle issue?
If not, what is the proper rear axle to complement the OD trans?

I think you have all convinced me to slow down a bit. I am going to go ahead and pull the 904 out and see what is leaking. If it is something I can fix, it may just be worth going that route. I really had no issues with it until it lost pressure because of this leak.

I am trying to think long term and want to be able to take this car on some long hauls.
So, lots to think about.

 

[MONC440]

If the converter clutch on the 518s are like the 904-family transmission in my '80 Newport 360 2bbl, it works off of spring pressure vs. fluid pressure, which can be tailored to your needs and rear axle ratio. The earlier (as in '76) TFs had the lockup at 27mph, which was like putting a manual trans in "high" and driving in that gear until you needed a downshift. My '80 Newport hits lockup at about 56mph, above an rpm level which would lug the engine and at a speed range from which there is enough engine power to not need a downshift for normal highway driving. That covers the torque converter lockup, as I know and have experienced it. Still, when the converter gets worn, it can shudder when it locks up and a load is present (as in acceleration or going up a hill). Only way to stop the shudder is to back out of the throttle (removing the load) or use enough throttle to downshift and get past that lockup speed/load situation so a smooth lockup can occur. NOT to forget that the converter and transmission input shafts are hardened, otherwise the converter splines can wear and cause "spin-out" where the converter splines are worn-down too much. Been there, twice.

The OD is electric, so a toggle switch can do that. Unless you get the vac harness and electrical items from a late '80s Chevy pickup truck. They used vac-operated switches to control the electrical lock-up for cruise and unlock for deceleration, and then re-lock for cruise conditions. Getting them at the right value for your vehicle might take some time, so the transmission stays locked-up for best results. An example: Initial lockup at vac above 12" Hg in 3rd or OD, unlock at 8" Hg, then re-lockup at 12"Hg; unlock above 18" Hg for coast-down. But GM also used a valve body switch so that some transmissions would lock-up in 2nd gear, which could be deactivated by somebody who knew what to disconnect. Just a suggestion of how to make things more automatic rather than use a toggle switch. Might be more trouble than it's worth?

KEY thing is all of this is that when going to a more modern automatic transmission, it is not just a bolt-in situation, although it was later a factory option. Past the installation part, the unit must be adapted to other things for your vehicle too. Whether analog or electronic. Which makes getting your existing transmission fixed or rebuilt the best fiscal option for a quick and less expensive situation, plus fewer "teething issues" of getting all of the adaptations done correctly. Even going to a later model 904-family transmission can have its adaptation issues due to the lock-up torque converter timing.

Just some thoughts,
CBODY67

The 518 use a solenoid for the lock up and a separate one for OD. Non of the 518's use the hydraulic lock up like the old 904 or 727. For the 518 I have always used a toggle switch that controls both solenoids at the same time. You have to treat it like a manual control and if you forget to turn in off it will stall the engine when you try to stop because the TC is locked. The only downfall of doing it this way is if you put a bunch of torque on it when it is applied you could slip the converter clutch. I have had this setup behind a 500HP 440 and I just never dropped the hammer with it engaged, with a 318 application that doesn't have a bunch of torque I don't think this would be an issue. My dad went the GM route that CBODY67 suggested in a hot rod but he was never really happy with the way it worked. It seamed to engage and disengage to much. The trans went out after about 20K miles and I don't know for sure but I always suspected that system was the cause.

 

[MONC440]

I really appreciate all the feedback.

It seems there is a real case for saving the 904.
I did call my local highly recommended shop about rebuilding the 904 and they said 1500.00.
Which is why I felt if I was going spend that kind of money I could get an upgrade for the same price.

If I go for the RE version, which is likely just because of availability, I was considering using the following controller which seems like it could allow me to set my shift points and lockup.
Has any one had experience with this controller?
E-Trans Controller: E-Trans Control

For me, the OD is really only for freeway driving. I rarely get over 50 around town where this car will spend most of it time.
If I am able to set the lock up close to 60 like CBODY67, does that solve the rear axle issue?
If not, what is the proper rear axle to complement the OD trans?

I think you have all convinced me to slow down a bit. I am going to go ahead and pull the 904 out and see what is leaking. If it is something I can fix, it may just be worth going that route. I really had no issues with it until it lost pressure because of this leak.

I am trying to think long term and want to be able to take this car on some long hauls.
So, lots to think about.

$1500 for a 904 rebuild seams a little high to me. They are one of the easiest transmissions to rebuild and the parts are not that expensive. If you were closer to Michigan I would do it for you for about $900. For $1500 make sure you are getting all new bushings, torques converter, clutches, rear sprag rebuilt and valve body disassembled and cleaned.

I have never used the controller you asked about but I checked out the site and it looks like it will work nicely.

The main benefit of the OD is to switch to a better gear ratio. What is your gear ratio now? In a heavy car with a small block switching to a 3.55, or even a 3.91 would really wake it up. IMO the 3.73 ratio would be about perfect. That is not a traditional Mopar ratio but works nice.
For a daily driver I try to get close to what the non OD RPM is at cruising speed. The factory designed these cars for a 70 MPH highway speed and optimized the RPM of the engine for that speed. If You keep the same gear ratio with OD and it comes on at 60 MPH then the RPM might drop down far enough that the engine can't handle the load. This isn't as big as an issue with a big block but I think the 318 will struggle. As an example say the 318/904 RPM is around 2300 @ 65MPH with a 2.91 rear gear. When you switch to a OD and don't change anything else your RPM is going to drop to around 1700RPM. Is your 318 making enough torque at the RPM to keep up with the load IDK. Now if you switch to a 318/518 with a 3.55 gear your RPM in OD at 65 would be around 2000. And that should be a good for the 318. With a 3.73 gear the RPM would be around 2150 and a 3.91 would be around 2300. As you can see the 3.91 would give you the same RPM at highway speed but much better performance in the lower gears. With a 3.91 your starts from a dead stop would be night and day compared to what you have now.

If your 904 was leaking and you didn't run it to long on low fluid, making it slip you could be ok with just putting in a new seal. If you did drive it slipping for any length of time then you will need the clutches replaced at a minimum and maybe some hard parts also.

Just my thoughts.

 

[secondChanceFury]

$1500 for a 904 rebuild seams a little high to me. They are one of the easiest transmissions to rebuild and the parts are not that expensive. If you were closer to Michigan I would do it for you for about $900. For $1500 make sure you are getting all new bushings, torques converter, clutches, rear sprag rebuilt and valve body disassembled and cleaned.

I have never used the controller you asked about but I checked out the site and it looks like it will work nicely.

The main benefit of the OD is to switch to a better gear ratio. What is your gear ratio now? In a heavy car with a small block switching to a 3.55, or even a 3.91 would really wake it up. IMO the 3.73 ratio would be about perfect. That is not a traditional Mopar ratio but works nice.
For a daily driver I try to get close to what the non OD RPM is at cruising speed. The factory designed these cars for a 70 MPH highway speed and optimized the RPM of the engine for that speed. If You keep the same gear ratio with OD and it comes on at 60 MPH then the RPM might drop down far enough that the engine can't handle the load. This isn't as big as an issue with a big block but I think the 318 will struggle. As an example say the 318/904 RPM is around 2300 @ 65MPH with a 2.91 rear gear. When you switch to a OD and don't change anything else your RPM is going to drop to around 1700RPM. Is your 318 making enough torque at the RPM to keep up with the load IDK. Now if you switch to a 318/518 with a 3.55 gear your RPM in OD at 65 would be around 2000. And that should be a good for the 318. With a 3.73 gear the RPM would be around 2150 and a 3.91 would be around 2300. As you can see the 3.91 would give you the same RPM at highway speed but much better performance in the lower gears. With a 3.91 your starts from a dead stop would be night and day compared to what you have now.

If your 904 was leaking and you didn't run it to long on low fluid, making it slip you could be ok with just putting in a new seal. If you did drive it slipping for any length of time then you will need the clutches replaced at a minimum and maybe some hard parts also.

Just my thoughts.

Thank you very much for the detailed explanation. Starting to make sense.
I will look into making adjustments to the gear ratios. "waking it up" sounds pretty good to me.
The trans showed no sign of slipping until it just "felt" like it went into neutral and never came back. I towed it home and am now weighing my options.
If it is as easy as replacing a seal, money wise that may be hard to pass it up. Driving it is more important than the upgrades if the repair is considerably cheaper.

Again, thank you very much the information. I feel better having as much to consider as possible.

 

[MONC440]

After you pull the trans if you can find a knowledgeable Mopar trans guy in your area you can bench test it before putting it back in. I can walk you thru it but it does include pulling the valve body, easy on a Mopar because the valve body is one piece. Then you have to have an air supply to pressurize each hydraulic circuit. You can test the apply of the front and rear clutch as well as the front and rear bands. Sounds complicated but it isn't. This doesn't 100% guarantee the clutches are good but it does show them engaging because if they don't engage with air there will be no need to put it back in without a rebuild.

Another option is to fill it with trans fluid and take a quick drive, before the fluid gets to low, and make sure all the gears work. Then you know it works and just needs the front seal replaced.

 

[Loadrunner]

Hello, My 904 is puking trans fluid out of the front of the bell housing.

What would you do if you were me?

It's the front seal on the pump, but why is it leaking, is the front pump bushing shot allowing the converter to wallow around?

Get a kit and learn how to rebuild a 904, and do a Transgo dash 2 valvebody mod.

Rebuilding a Torqueflight is fun, and can turn into a profitable hobby.

Always flush the converter lines/core super well with solvent and air when doing a swap if there any signs of trans failure.

You can usually tell everything about a trans looking in the pan for clutch material, but in a junk yard situation the trans might be little worn but have dried out seals, meaning just a short lived install with problems leading to failure.

 

[Loadrunner]

Or you could just pull the tranny out, lower it, change the front seal and bushing if needed, put it back in and drive.

One seal leaking = fix one seal.

Are your converter bolts tight, is it the right converter, balanced correctly for your crankshaft application?

If it's not balanced properly, shakes, it will wipe out a pump seal a lot faster, regardless of trans.

Get some ATF on your - gloved - hands, play with it. Learn something about making a Mopar run. All of this was well known before the internet, before the legions of Youtube video fails.

904 Torqueflite Transmission - New Old School - Mopar Muscle Magazine

 

[493mike]

I agree with the "you can rebuild the transmission yourself" gang. Buy a rebuild book for tips and specs. Do the rebuild by sections: front clutch, rear clutch, gear train, case, and lastly the valve body. Just clean every part and assemble with Dexron fluid for lube or buy some assembly lube. A FSM would be a help also. The 69 valve body already shifts quite firmly so you don't really need a shift kit. Rock Auto sells everything you need-cheap. Come on in, the water's fine!
Mike

 

[Big_John]

I have to agree with fixing what's there rather than replacing.

Doing a conversion sounds great until you see the amount of work and $$ involved and then you will have a hard time justifying any of it. Being a pleasure car you drive occasionally means it would take you a lot of years to recover it through gas savings and I doubt if you will ever see any savings in driveline wear.

So, if it were me, I would repair what you have. If you have to pull the trans, I would, at minimum, do a complete "reseal" of the trans. Basically, all the external gaskets and seals. I'd also give some thought to doing a rebuild, although that would depend on the condition (mileage etc.) of the existing trans. They aren't that hard to rebuild yourself if you take your time, but that's your call.

All that said... Are you sure it's leaking from the front seal? The dipstick tube and the shifter seal are the usual culprits and can mimic the front seal when the oil collects and drains down around the bellhousing. I don't want to see you take the time without checking this stuff first.

 

[Loadrunner]

The voice of reason.

Troubleshoot, although puking from the bellhousing is pretty unmistakable.

Other sources of leaks - very few - dipstick tube, shift shaft, speedo gear, tailshaft, again bushing can we worn out from bad U joints, cooler lines/fittings, pan gasket.

Most people I've met, even in the trade, have no clue how to install a trans pan gasket correctly.

Tip; Buy Fel Pro cork/rubber gasket and follow the directions.

 

[secondChanceFury]

I really appreciate all the feedback.
I am leaning heavily toward repairing it. At a minimum, bushing, seal and maybe the converter.

I know without a doubt it is coming from the bell housing at this point. I pulled the pan and added new filter, cleaned everything real good and refilled it.
Had no leaks while I was warming it up... as soon I dropped it into gear it engaged. Felt great. I went back and forth a few times in the garage.
Was considering a test drive when I looked under the car... There was a bit of a mess. it was a steady drip when not engaged.
I put a camera on it and then put it in gear... and while engaged it just pours out.
Interestingly, because of all the feedback I have been watching a few rebuild videos. Does not look as fragile as I imagined.
Going to take it a step at a time. May take me a few weeks to actually get to pull it.
I will definitely keep the thread informed.
Thank you again.

 

[MONC440]

I really appreciate all the feedback.
I am leaning heavily toward repairing it. At a minimum, bushing, seal and maybe the converter.

I know without a doubt it is coming from the bell housing at this point. I pulled the pan and added new filter, cleaned everything real good and refilled it.
Had no leaks while I was warming it up... as soon I dropped it into gear it engaged. Felt great. I went back and forth a few times in the garage.
Was considering a test drive when I looked under the car... There was a bit of a mess. it was a steady drip when not engaged.
I put a camera on it and then put it in gear... and while engaged it just pours out.
Interestingly, because of all the feedback I have been watching a few rebuild videos. Does not look as fragile as I imagined.
Going to take it a step at a time. May take me a few weeks to actually get to pull it.
I will definitely keep the thread informed.
Thank you again.

Great! Just reach out if you get stuck. I would suggest supporting Cope Racing Transmissions for the rebuild kit. Not only will John give you the right components for your application he will also give you tech advise if you need it. On top of that he is a life long Mopar guy.