New Torque converter, rear gear change?

[Sir Dodge alot]

Hello wizards of the C body forums.
I've got a question.

I've got my transmission out while I'm rebuilding it.

Probably at a later date, I'd like to replace the 2.76 gears to run 2.94 gears.

Now as my transmission is out, and I've got a torque converter chosen.

Will a different torque converter be needed to accommodate the 2.94 gears?

The time I ordered a torque converter, I was using the 2.76 gears as a template, will this affect drivability warranting a Torque converter change to use the 2.94 gears?

Sorry if that sounded convoluted and confusing.
Thanks in advance.

 

[CBODY67]

2.94 gears make a difference? Don't expect very much at all. Might not even be worth the money spent to get and install them. No need to get a different torque converter for that reason.

Back then, Chrysler seemed to want their engines to run in a particular rpm range at 60mph. The reason the Imperials got 2.94s was to compensate for the larger diameter tires they used back then. Hence the 2.94 in an Imperial would have a cruising rpm similar to a Chrysler with 2.76s.

2.94s were usually used with A and LA motors to make them a bit more competitive against Chevys with 3.08s and 3.36s, or Fords with 3.0 and 3.25s.

Just some thoughts,
CBODY67

 

[Sir Dodge alot]

2.94 gears make a difference? Don't expect very much at all. Might not even be worth the money spent to get and install them. No need to get a different torque converter for that reason.

Back then, Chrysler seemed to want their engines to run in a particular rpm range at 60mph. The reason the Imperials got 2.94s was to compensate for the larger diameter tires they used back then. Hence the 2.94 in an Imperial would have a cruising rpm similar to a Chrysler with 2.76s.

2.94s were usually used with A and LA motors to make them a bit more competitive against Chevys with 3.08s and 3.36s, or Fords with 3.0 and 3.25s.

Just some thoughts,
CBODY67

Hi appreciate the reply, thanks.

I have 14 inch stock wheels, comparing to the imperials, the 14 inch with 2.94 gears will see some RPM on highway cruising?

I'll stick with the same Torque converter then.
Thanks!

 

[67_300_Convertible]

If I'm doing the math right, you are looking at 6.5% higher RPM with 2.94's vs. 2.76's for a given vehicle speed. That would result in an RPM difference of around 163 RPM at cruise (assuming your old cruise RPM was around 2500). Would you notice that small a difference anywhere but on a digital tachometer?

 

[Sir Dodge alot]

If I'm doing the math right, you are looking at 6.5% higher RPM with 2.94's vs. 2.76's for a given vehicle speed. That would result in an RPM difference of around 163 RPM at cruise (assuming your old cruise RPM was around 2500). Would you notice that small a difference anywhere but on a digital tachometer?

Appreciate the calculations, that's handy to know.
I just figured the stop and go traffic is what makes the car gutless with the 2.76 gears.

I'm not keen on giving up the highway cruising ability, but don't want to kill my mileage with anything like a 3.23 or higher gears.

And with the 2.94's it'll slightly feel less doggy when the traffic light goes green.

I suppose the 2.94 gears fits the bill.
Going to get a set at a later date when able.

 

[CBODY67]

Thing is "gutless" has different meanings to different people. To me, the 2.76s are fine for city driving, especially after I added two more turns to the kickdown rod preload to raise the part-throttle shift points several mph. That was way back in 1972 and no trnamission issues yet (on the factory non-rebuilt transmission). Since then, I've done the same thing with my '70 Monaco and '80 Newport 360 2bbl.

To me, the fact is that almost any 4cyl turbo with a 6+speed automatic will make our cars look slower than they really are. Unless something like 3.73 rears are in the back OR an 8-spd TF is swapped in (with its very deep low gear).

In addition to adding the little bit of additional preload, I also had the ign timing advanced from 12.5 to 15 degrees BTDC, which added a bit of extra off-idle response. PLUS only using an initial 1/4 to 1/3 punch off-idle, then letting the higher upshift speeds work. THAT keeps the vac advance can charged to keep more advance in the distributor, too, for best results. Quicker acceleration with less throttle is fine by me. Plus a hair better fuel economy as the carb is not into the power circuit as much, if at all.

Personally, I'll take "on-highway" over "in city" performance, then as now. Especially now that Interstate traffic down here moves at 75-80mph in a posted 70mph zone. Of course, when traffic is gridlocked at 20mph, that "70" sign is meaningless.

In the '80 Newport, last time the lock-up converter "spun out", they installed the 2.75 low gar planetary instead of the normal 2.45. That car has a 2.45 rear axle ratio, so it kind of put things back "normal" with 2.75 x 2.45 vs 2.45 low gear and 2.76 rear axle combination of old. I could tell a slight bit of difference in acceleration, but not much. Anybody who didn't know would not notice, usually.

Enjoy!
CBODY67

 

[69CoronetRT]

Appreciate the calculations, that's handy to know.
I just figured the stop and go traffic is what makes the car gutless with the 2.76 gears.

I'm not keen on giving up the highway cruising ability, but don't want to kill my mileage with anything like a 3.23 or higher gears.

And with the 2.94's it'll slightly feel less doggy when the traffic light goes green.

I suppose the 2.94 gears fits the bill.
Going to get a set at a later date when able.

The nominal difference between 2.76 and 2.94s will not be felt enough to justify the time and money spent to make the conversion. Make it worth while and go to 3.23. You'll feel that difference. You can get gas efficiency with that ratio.

kill my mileage. Is this a daily commuter vehicle? If you have a C body and are worried about mileage difference in the few miles you will drive per year, you are in the wrong hobby. The gas savings will be negligible and, frankly, the cost of driving a vintage vehicle just part of doing business in the hobby. If you are concerned gas mileage and 'cost to operate' a driver/ice cream stand/cruise in car, a /6 A body might be a better fit.

 

[Sir Dodge alot]

The nominal difference between 2.76 and 2.94s will not be felt enough to justify the time and money spent to make the conversion. Make it worth while and go to 3.23. You'll feel that difference. You can get gas efficiency with that ratio.

kill my mileage. Is this a daily commuter vehicle? If you have a C body and are worried about mileage difference in the few miles you will drive per year, you are in the wrong hobby. The gas savings will be negligible and, frankly, the cost of driving a vintage vehicle just part of doing business in the hobby. If you are concerned gas mileage and 'cost to operate' a driver/ice cream stand/cruise in car, a /6 A body might be a better fit.

Yes this is my daily driver, I drive to college back and forth (16 miles or so) but due to some transmission issues, I'm currently rebuilding the A727.

I suppose kill my mileage is going a bit far, I managed to get close to 18.5 previously 21 Or so? I'd like to keep it that way, or similar.
MPG on a highway cruise might decline, but I reckon 2.94's are better off the line, is quite a good "compromise" gear.

I know it's useless trying to "compete" against modern traffic but I'd just like to get off the line a bit faster, but not looking for a drag racer gear really.

The 3.23's are good for sure, but their expensive if I do find one.

I did consider getting an A body valiant, but the styling of the forward look cars is more of my "speed" lol.

But really I'm getting similar MPG numbers comparable to a Chevy Tahoe, I'm quite pleased with that, just the off the line grunt is what I'm after, but not overkill.

Appreciate the feedback, I'll ponder on the decision of whether to keep the 2.76's.
Thanks.

 

[Sir Dodge alot]

Thing is "gutless" has different meanings to different people. To me, the 2.76s are fine for city driving, especially after I added two more turns to the kickdown rod preload to raise the part-throttle shift points several mph. That was way back in 1972 and no trnamission issues yet (on the factory non-rebuilt transmission). Since then, I've done the same thing with my '70 Monaco and '80 Newport 360 2bbl.

To me, the fact is that almost any 4cyl turbo with a 6+speed automatic will make our cars look slower than they really are. Unless something like 3.73 rears are in the back OR an 8-spd TF is swapped in (with its very deep low gear).

In addition to adding the little bit of additional preload, I also had the ign timing advanced from 12.5 to 15 degrees BTDC, which added a bit of extra off-idle response. PLUS only using an initial 1/4 to 1/3 punch off-idle, then letting the higher upshift speeds work. THAT keeps the vac advance can charged to keep more advance in the distributor, too, for best results. Quicker acceleration with less throttle is fine by me. Plus a hair better fuel economy as the carb is not into the power circuit as much, if at all.

Personally, I'll take "on-highway" over "in city" performance, then as now. Especially now that Interstate traffic down here moves at 75-80mph in a posted 70mph zone. Of course, when traffic is gridlocked at 20mph, that "70" sign is meaningless.

In the '80 Newport, last time the lock-up converter "spun out", they installed the 2.75 low gar planetary instead of the normal 2.45. That car has a 2.45 rear axle ratio, so it kind of put things back "normal" with 2.75 x 2.45 vs 2.45 low gear and 2.76 rear axle combination of old. I could tell a slight bit of difference in acceleration, but not much. Anybody who didn't know would not notice, usually.

Enjoy!
CBODY67

Appreciate the feedback, & write up.
Very good points you mentioned.
I'll put the 2.76 replacement on the shelf for now.

 

[70bigblockdodge]

I would go with what @CBODY67 said about raising your timing to help stoplight to stoplight. Timing is lazy on most of these cars. The factory initial timing is for smooth idle and nice drivability without possible starter kickback and pinging with a tank of crap gas, later for emissions an engine always makes less HC with less timing. Your not too far off if your getting 18+ mpg. 3.23 gears really need to be paired with 15" wheels otherwise you are into the 3k plus range to cruise 70-75 mph, yes you can get respectable mpg with them, but the engine noise and all day fatigue that it brings is not worth it. If you can get 2.94 for basically nothing sure. I would just leave the 2.76.

 

[70bigblockdodge]

Personally, I'll take "on-highway" over "in city" performance, then as now. Especially now that Interstate traffic down here moves at 75-80mph in a posted 70mph zone. Of course, when traffic is gridlocked at 20mph, that "70" sign is meaningless

100% agree with this. I put 1900+ miles on my Charger last year's power tour in a week. 3.23 with 15" wheels and OD trans 2600rpm is around 80 mph. It's a .72 od gear. So let's put it back to 1:1 trans 2600×1.28=3328, sure that would be fun for 1900 miles ringing in your ears. For all the 3.55 geared guys I'll be finished with dinner and 3-4 beers in when you get there.

 

[Sir Dodge alot]

I would go with what @CBODY67 said about raising your timing to help stoplight to stoplight. Timing is lazy on most of these cars. The factory initial timing is for smooth idle and nice drivability without possible starter kickback and pinging with a tank of crap gas, later for emissions an engine always makes less HC with less timing. Your not too far off if your getting 18+ mpg. 3.23 gears really need to be paired with 15" wheels otherwise you are into the 3k plus range to cruise 70-75 mph, yes you can get respectable mpg with them, but the engine noise and all day fatigue that it brings is not worth it. If you can get 2.94 for basically nothing sure. I would just leave the 2.76.

The timing is one of the first things I bumped up, around 14 to 15 BTDC,

(I think I experimented with at least 25 BTDC but you can go up to 21 BTDC without the starter kicking back)

I recurved the stock distributor as well. 2 light springs that seems to make the engine torque to the point I think the stock engine mount broke.

Regarding the pricetag for the 2.94's that I found were 200 some odd dollars, include shipping, maybe somewhere around $280 or so?

I honestly don't know what is a good price even for the 3.23's, last I saw one was for $1200, it's about the price tag I paid for the whole car.

Both 2.94's and the 3.23's were open diff peg leg style.