My engine is being a jerk!

[C Sickness]

I have been gradually working through the issues on my new to me 1970 300, which was inop for 30 years. The car now starts and runs reliably. Ive been very gentle driving it around the neighborhood, just light throttle, no W.O.T. starts.

That's a good thing, as the driver side motor mount was sheared. Just a moderate throttle
would at times send the fan into the fan shroud. All mounts are now new.

I checked the new mounts the other day by opening the hood, standing on the brake, and giving it a bit of throttle. Engine torque would make the driver's side of the engine "hike up" against the load. (BTW, it's impressive to see that bonded rubber block in the mount stretch to control the engine against load. No surprise that they want to break.)

During this load test, the engine would sometimes "unload", fall down, and then jerk back up, even though throttle was constant. I think this has also happened while driving with moderate throttle after a stop. There's sometimes a "clunk" or "chuggle".

This makes me think that the transmission plates must be slipping ,momentarily . I have not touched the trans yet, other than confirming the level is correct. On the plus side, the car has only 44K original miles. The minus side is, of course, that it's 50 years old. I'm going to change the fluid and filter. Maybe the filter is "pasted" or restricted, resulting in starvation, and low clutch circuit pressures?

Also, if the car sits a couple days, is started and put into gear, either forward or reverse, the car doesn't move until i give it a bit of throttle. Maybe another indicator that it's "starved", or has "drained back". Once the car warms up, the trans is normal. Drop it into gear, and it will creep.

I saw a good looking 727 book on Amazon. Looks like it could be rebuilt with only a couple special tools, like slide hammers.

I don't know if I can make it run acceptably until rebuild time.

 

[1970FuryConv]

During this load test, the engine would sometimes "unload", fall down, and then jerk back up, even though throttle was constant. I think this has also happened while driving with moderate throttle after a stop. There's sometimes a "clunk" or "chuggle".

This makes me think that the transmission plates must be slipping ,momentarily . I have not touched the trans yet, other than confirming the level is correct. On the plus side, the car has only 44K original miles. The minus side is, of course, that it's 50 years old. I'm going to change the fluid and filter. Maybe the filter is "pasted" or restricted, resulting in starvation, and low clutch circuit pressures?

Also, if the car sits a couple days, is started and put into gear, either forward or reverse, the car doesn't move until i give it a bit of throttle. Maybe another indicator that it's "starved", or has "drained back". Once the car warms up, the trans is normal. Drop it into gear, and it will creep.

Hi C
If you have a 30 year old filter in your trans, I suspect it is clogged, or disintegrated and sending particles throughout the system. I agree with immediate fluid and filter change. You may even have to change the filter twice to get all the junk out of the system. Smooth flow to the front pump is key for smooth operation. Bad filter can block that.

I think the drain back issue is nothing to worry about. My 70 440 does it as well as my 72 360, both have 727 trans. Best of luck, Ben

 

[CBODY67]

I concur, the drain-back after sitting dormant for even overnight, is a common trait of TFs after their first atf change past the factory-fill. Only if you start it in "P", typically, but not nearly as bad if you start it in "N", from my experiences. When our '66 Newport was new-to-us with 7100 miles, cold starts in "P" were no real problem, but after the first recommended atf/filter change, then the drain-back issue occured.

I know the dacron filter seems to be preferred, but my transmission operative, who is very well-versed in all things TF, prefers the fine-wire brass filter. His reasoning is that when the engine stops, the fluid above the filter will wash out any accumulation of debris that has been caught by the filter, decreasing "clog" situations. Kind of makes sense. FWIW

Enjoy!
CBODY67

 

[saforwardlook]

I saw a good looking 727 book on Amazon. Looks like it could be rebuilt with only a couple special tools, like slide hammers.

Rebuilding a 727 isn't as easy as that book is making it sound if you are led to believe a couple special tools like slide hammers are all that are required. Actually, the factory service manual is really pretty good and complete about what is needed in terms of special tools and what detail steps you will need to take to rebuild one. I am not saying it is hard, but the first time doing one isn't easy either and some special tools that aren't real cheap are pretty much a necessity IMO.

 

[69monaco]

Also, if the car sits a couple days, is started and put into gear, either forward or reverse, the car doesn't move until i give it a bit of throttle. Maybe another indicator that it's "starved", or has "drained back". Once the car warms up, the trans is normal. Drop it into gear, and it will creep.

The oil level is correct ?
I would try a 1/4 gallon more first.

 

[Mr C]

I always cycle my Mopars to Neutral before pulling away to run the pump and build pressure.

Your "no move" symptom is classic converter drain back/ low fluid.

 

[CBODY67]

When the trans is in "P", the line pressure is like 15psi, which is basic "lube" pressure. When in "R", it's quite a bit higher, and somewhere in-between when in "D". BUT until the new atf is installed, with a new filter of choice, how the trans is acting and why is purely open to speculation as to its condition. Certainly, the after-it-sits sluggish engagement for that first engagement of the day is normal for TFs, from our experiences, until the fresh fluid and filter are installed, no real judgments/assessments can be accurately made.

Until the torque converter gets fully full, from pump operation, vehicle movement can be delayed . . . at any rpm. You might consider it to be an unnecessary hassle to remember to start the vehicle, with the brakes applied, in "N" rather than "P", but as mentioned, for that first start of the day, especially in colder weather, things just work better.

Back in the later 1960s, this issue was inquired about in a CAR LIFE magazine column. Their answer was that from what they could determine, the orig factory-fill atf was a multi-vis fluid, which was not available to the general public. Not sure if that's accurate or not, even back then, as atf is pretty thin as it is. Just relaying what was said, back then.

Enjoy!
CBODY67

 

[saylor]

glad yall aint doctors.

if you are 'standing on the brake' and giving it throttle - what gear are you in? why do you think the transmission is involved with this test you did? Because you saw the motor moved?

the converter drainback is normal, expected, and doesnt need 'another half gallon' of fluid holy crap.

it is known to sit in N and let it fill up, etc., etc.

try not to die -

- saylor


P.S. - now, boys and girls, why do these cars stumble under light throttle, which is what i think he is trying to describe.

 

[Ross Wooldridge]

I will not attempt an armchair diagnosis on the chuggle description, but regarding the trans drain back I can throw this out there (and it goes for everybody experiencing this):

AFAIK, since this happened to me and necessitated a rebuild - trying to drive the car while it slips as described will burn the clutch material off the bands and clutch pack rings (not sure what they're called). As mentioned, the pump doesn't run in Park, so I always set my p brake and start the car in Neutral if it's been sitting, and wait a few seconds for the pump to refill the trans. Don't allow it to slip...

 

[Big_John]

Just to make sure... and we've seen this happen a couple times... You are checking trans fluid level in neutral with the engine running and not park, correct?

Not trying to insult, it has just tripped a couple guys up after all the comments made and they were all set to tear the trans out for rebuild and come to find out, the level was being checked in park. I like to cover ALL the bases, and not take system knowledge for granted anymore.

If level is OK, I'd pull the pan and take a look at any obvious junk in the pan or jelled fluid clogging the filter. Fresh fluid might do the trick or buy you some time at least.

The 727 is a pretty easy trans to rebuild compared to others. I've done a few. The FSM does cover it well, but quite frankly, it can be done without the expensive Miller tools listed there. There are alternatives and a couple "work arounds". I had a friend once show me (he was a factory trained trans guy) some really simple and fast ways to do the clutches. Just really common sense and a well equipped shop.

A simple rebuild/freshening is easy.... Where it gets hard is figuring out a problem and fixing it. A problem spotted by an old pro that's done a couple hundred is frustrating to a novice that goes through the steps and has to pull the trans back out because it doesn't work. In other words, think about "risk versus reward" on this one.

If you really want to do it, build a stand or at least a bench with a hole in it to stick the tail in and hold it with the bell housing pointing up while you assemble it.

This is a great book on the subject. https://smile.amazon.com/Torqueflit...s=727+transmission+book&qid=1609078485&sr=8-1

 

[C Sickness]

Just to make sure... and we've seen this happen a couple times... You are checking trans fluid level in neutral with the engine running and not park, correct?

Not trying to insult, it has just tripped a couple guys up after all the comments made and they were all set to tear the trans out for rebuild and come to find out, the level was being checked in park. I like to cover ALL the bases, and not take system knowledge for granted anymore.

If level is OK, I'd pull the pan and take a look at any obvious junk in the pan or jelled fluid clogging the filter. Fresh fluid might do the trick or buy you some time at least.

The 727 is a pretty easy trans to rebuild compared to others. I've done a few. The FSM does cover it well, but quite frankly, it can be done without the expensive Miller tools listed there. There are alternatives and a couple "work arounds". I had a friend once show me (he was a factory trained trans guy) some really simple and fast ways to do the clutches. Just really common sense and a well equipped shop.

A simple rebuild/freshening is easy.... Where it gets hard is figuring out a problem and fixing it. A problem spotted by an old pro that's done a couple hundred is frustrating to a novice that goes through the steps and has to pull the trans back out because it doesn't work. In other words, think about "risk versus reward" on this one.

If you really want to do it, build a stand or at least a bench with a hole in it to stick the tail in and hold it with the bell housing pointing up while you assemble it.

This is a great book on the subject. https://smile.amazon.com/Torqueflit...s=727+transmission+book&qid=1609078485&sr=8-1

I was just thinking about this. We need to clarify if the pump is, or is not, running in Park. Someone said the pump is running all the time, but at a low "maintenance" pressure when in park. If so, then the dipstick should be the same in park or neutral.

If the pump doesn't run in park, then the sump would be higher than the sump would be in neutral, or any of the drive gears.

It would seem logical that the dipstick should be checked in park, for safety reasons. Maybe that's wrong.

 

[C Sickness]

I just read the operator's manual. It says set the parking brake, and check level in neutral!

 

[C Sickness]

John, your point about a proper work area is well taken. I used to be on the BMW forum. Watched a member rebuild a ZF in his living room, on the carpet. Final assembly was on top of the coffee table.

Another member needed to clean the gunk and carbon out of his intake manifold. Put it in the dishwasher. Didn't get it all clean. The white dishwasher was no more. The pics he posted were simply amazing. Another member suggested he run it again, but turn off the water, and run it on pure mineral spirits.

I would probably leave before the "heated dry" cycle came on........

 

[70bigblockdodge]

Is it revving up when the engine falls back into position or is the rpm dropping.
If it revs it could be trans. If it drops it is most likely fuel /ignition.

 

[C Sickness]

Is it revving up when the engine falls back into position or is the rpm dropping.
If it revs it could be trans. If it drops it is most likely fuel /ignition.

I have been through all the ignition and fuel system. Engine is running very smooth. Even with the new soft engine mounts, barely a wiggle at idle. We all know what an engine with fuel and/or ignition issues is like. It wants to jump out of the car all day long. Mine is not that. The cliche' "Swiss Watch" comes to mind.

When loading against the brake, engine RPM, tone, and exhaust note are all rock steady. It unloads and loads very quickly, probably a fraction of a second. Just enough to fall down and hike up. As if it slips for just a couple revs and catches again. Not enough time for the RPM to make much of a change.

I suspect it's slipping, and don't want to do any more "testing" lest I burn plates. Fluid and filter are up next. Change them every 50 years, even if they don't need it.

 

[C Sickness]

I appreciate Monaco's suggestion to double check the fluid level, which could be low by some portion of a quart. His translation didn't use the word "quart", but I understood what he was saying.

 

[Big_John]

I was just thinking about this. We need to clarify if the pump is, or is not, running in Park. Someone said the pump is running all the time, but at a low "maintenance" pressure when in park. If so, then the dipstick should be the same in park or neutral.

If the pump doesn't run in park, then the sump would be higher than the sump would be in neutral, or any of the drive gears.

It would seem logical that the dipstick should be checked in park, for safety reasons. Maybe that's wrong.

Yea, the pump doesn't "run" in park, and by that I mean it doesn't push fluid through the convertor.

Fluid level is pretty critical to how it all works. Overfill isn't good either as the fluid gets up into the rotating assembly and starts to foam.

The level will be a lot higher in park. Higher when hot and lower when cold. Best to check when hot and has to be in neutral. Checking it cold just means it should be above the "add" mark and maybe halfway to the full mark. This seems to vary car to car (in my experience anyway). Adding means pints or half pints and not full quarts to get correct level.

I have also once had a dipstick that the cap wasn't attached at the locating notch and the cap was moving up the dipstick and it would push farther into the tube. So it appeared I had more fluid than I did.

 

[Ross Wooldridge]

As well, I have been told by trans experts to not only check in Neutral with everything warm, but to actually click the trans through all gear settings for a few seconds prior to checking the dipstick.

 

[Big_John]

As well, I have been told by trans experts to not only check in Neutral with everything warm, but to actually click the trans through all gear settings for a few seconds prior to checking the dipstick.

You especially want to do that when checking cold or after refilling the trans with new fluid.

 

[CBODY67]

Please note in most service manuals, that there are TWO refill capacities listed. One is for a complete rebuild when the trans is "dry", other than assembly lube atf. The other is for "filter replacement", basically.

Start with a lesser amount of the total for filter replacement amount, then move up toward the end amount slowly, incrementally, until you get to the "ADD" mark on a completely warm transmission. If it's already there, then add pints until you get to about 1/2 way between "ADD" and "FULL". That way, no worries about over-filling and all that can mean. Should be fine when the ambient temps get very cold in the winter, usually.

I believe the procedure is, with the trans at operating temp (which happens best after about 10 miles of driving rather than just watching engine coolant temperature). Then put the selector lever into each position, foot brake applied, ending in "N". Then check the fluid level until the desired level is reached. Then take the car for a drive and see how things go. Recheck the fluid level for good measure.

Just some thoughts,
CBODY67