[C1] Changing ratios on a 1962 posi unit
10-09-2021, 08:39 AM
#1
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Changing ratios on a 1962 posi unit
I have done a search and turned up some real old threads (including great info from DZAUTO). My 1962 which I have owned since 1975 currently has 3.08 that I had installed back in the fuel crisis days. The car has a close ratio 4 spd and the combo has never had great take of from standing. (The engine is an LT-1). My question is: how difficult is it to change out the gear ratio? What ratio would you recommend for daily driving?
Thanks
Thanks
10-09-2021, 10:40 AM
#3
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It might be easier to swap the T-10 for a new Super T-10, There are three ratio sets available. I'd recommend the 2.88, 1.91, 1.33. 1.00:1 set. The other sets first gears are 2.64 and 2.43.
A 2.88 first gear with a 3.08 axle would be the same as a 4.03 axle with your 2.20 first gear T-10. All these Super T-10s have what I call "progressive" ratios. The 1-2 intergear ratio is fairly high and the intergear ratios become progressively smaller as you go through the gears, which is the way modern road car transmissions are set up.
If you have Excel search for threads started by me and download the gear chart spread sheet. It's interactive, so the user inputs all the gear ratios, tire revs/mi, and shift speeds. Then the program computes the intergear ratios, maximum speed in each gear, and where the revs drop to in the next higher gear, and if your good with Excel you can plot it out as speed versus revs for up to five or six gears.
Duke
A 2.88 first gear with a 3.08 axle would be the same as a 4.03 axle with your 2.20 first gear T-10. All these Super T-10s have what I call "progressive" ratios. The 1-2 intergear ratio is fairly high and the intergear ratios become progressively smaller as you go through the gears, which is the way modern road car transmissions are set up.
If you have Excel search for threads started by me and download the gear chart spread sheet. It's interactive, so the user inputs all the gear ratios, tire revs/mi, and shift speeds. Then the program computes the intergear ratios, maximum speed in each gear, and where the revs drop to in the next higher gear, and if your good with Excel you can plot it out as speed versus revs for up to five or six gears.
Duke
Last edited by SWCDuke; 10-09-2021 at 10:40 AM.
10-12-2021, 10:18 PM
#4
Racer
3:08 is ideal for Richmond 5 spd ratios, which I have in my 69 Camaro, 1st thru 4th very low ratios for great acceleration and the 1 to 1 in 5th gear so you can enjoy that 3:08. Not too difficult to find parts, new and used, to change the rearend. But a trans swap to a 5 or 6 speed would be the best of both worlds. Lower gears, higher number, will give you better acceleration but then you are trading off highway cruise as far as rpm, fuel economy and engine wear. That was the 60's and 70's but most of us didn't care!
C Ya, JM Rock
Frankenstein 59 (with T-56 6 spd and 3:73 rear gears)
C Ya, JM Rock
Frankenstein 59 (with T-56 6 spd and 3:73 rear gears)
10-13-2021, 02:42 AM
#5
Burning Brakes
I ran a similar ratio of 3.08 with a 5 speed (direct) Richmond in my 57 Corvette. the 3.30 (?) 1st gear in Richmond's and 3.08 give you an approx ratio of 10:1. I could wind that baby up in 1st put it in 2nd, nail it again and it would go a little sideways!
If your sticking with the 4 speed a 3.55 works all around good and is easy to do.
If your sticking with the 4 speed a 3.55 works all around good and is easy to do.
3:08 is ideal for Richmond 5 spd ratios, which I have in my 69 Camaro, 1st thru 4th very low ratios for great acceleration and the 1 to 1 in 5th gear so you can enjoy that 3:08. Not too difficult to find parts, new and used, to change the rearend. But a trans swap to a 5 or 6 speed would be the best of both worlds. Lower gears, higher number, will give you better acceleration but then you are trading off highway cruise as far as rpm, fuel economy and engine wear. That was the 60's and 70's but most of us didn't care!
C Ya, JM Rock
Frankenstein 59 (with T-56 6 spd and 3:73 rear gears)
C Ya, JM Rock
Frankenstein 59 (with T-56 6 spd and 3:73 rear gears)
10-13-2021, 08:59 AM
#6
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T-10 close ratio: 2.20, 1.64, 1.31, 1.00:1 ( Muncie CR third gear is 1.28. sometimes specified as 1.27.)
T-10 wide ratio: 2.54, 1.89, 1.51, 1.00:1 (Muncie WR ratios slightly different, but essentially the same as T-10 WR)
Richmond Five-Speed: 3.28, 2.13, 1.57, 1.23, 1.00:1
Richmond Super T-10: 2.88, 1.91, 1.33. 1.00:1
Richmond Super T-10 : 2.64, 1.75, 1.34, 1.00:1
Richmond Super T-10: 2.64, 1.60, 1.23, 1.00:1
Richmond Super T-10: 2.43, 1.61, 1.23: 1.00:1
A large displacement high torque bandwidth engine in a relatively light car doesn't need more than five speeds and four properly selected ratios is fine in most cases with overall first gear multiplication of 8-9:1 unless you live at high altitude and/or hilly/mountainous country.
With an 8-9:1 overall first, a base engine will easily pull a 2.73 axle, which yields about 2750 RPM at 80 with OE revs/mile tires. SHP type engines that offer less low end torque will be comfortable with a 3.08 axle that yields about 3100 at 80.
Unless you do more than 50 percent of your driving on long freeway trips the above revs at 80 are very reasonable for a vintage engine.
Also consider that a Richmond Super T-10 runs about $2K and the Richmond five-speed is nearly double that price, heavier, and I'm not sure how you get it into a C2 with a non-removable center cross member assuming it will fit in the tunnel... I don't know.
For a deeper dive download my gear chart Excel program referenced in post #3 and play some games.
Duke
T-10 wide ratio: 2.54, 1.89, 1.51, 1.00:1 (Muncie WR ratios slightly different, but essentially the same as T-10 WR)
Richmond Five-Speed: 3.28, 2.13, 1.57, 1.23, 1.00:1
Richmond Super T-10: 2.88, 1.91, 1.33. 1.00:1
Richmond Super T-10 : 2.64, 1.75, 1.34, 1.00:1
Richmond Super T-10: 2.64, 1.60, 1.23, 1.00:1
Richmond Super T-10: 2.43, 1.61, 1.23: 1.00:1
A large displacement high torque bandwidth engine in a relatively light car doesn't need more than five speeds and four properly selected ratios is fine in most cases with overall first gear multiplication of 8-9:1 unless you live at high altitude and/or hilly/mountainous country.
With an 8-9:1 overall first, a base engine will easily pull a 2.73 axle, which yields about 2750 RPM at 80 with OE revs/mile tires. SHP type engines that offer less low end torque will be comfortable with a 3.08 axle that yields about 3100 at 80.
Unless you do more than 50 percent of your driving on long freeway trips the above revs at 80 are very reasonable for a vintage engine.
Also consider that a Richmond Super T-10 runs about $2K and the Richmond five-speed is nearly double that price, heavier, and I'm not sure how you get it into a C2 with a non-removable center cross member assuming it will fit in the tunnel... I don't know.
For a deeper dive download my gear chart Excel program referenced in post #3 and play some games.
Duke
Last edited by SWCDuke; 10-13-2021 at 09:06 AM.
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Ol Blue (10-13-2021)
10-13-2021, 12:58 PM
#7
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The Richmond Super T-10 with 2.88 low would probably be a best bet combo, BUT, swapping ring & pinion is a whole lot cheaper than replacing the tranny, even if I have a professional 'set it up'. This is not really going to be a highway car, so I think I can live with a 3.70. I've got the winter to think it over as I am about to leave NH (and the 'vette) for the winter. I will continue to follow this thread with interest.
10-13-2021, 01:28 PM
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10-13-2021, 01:35 PM
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St. Jude Donor '12
T-10 close ratio: 2.20, 1.64, 1.31, 1.00:1 ( Muncie CR third gear is 1.28. sometimes specified as 1.27.)
T-10 wide ratio: 2.54, 1.89, 1.51, 1.00:1 (Muncie WR ratios slightly different, but essentially the same as T-10 WR)
Richmond Five-Speed: 3.28, 2.13, 1.57, 1.23, 1.00:1
Richmond Super T-10: 2.88, 1.91, 1.33. 1.00:1
Richmond Super T-10 : 2.64, 1.75, 1.34, 1.00:1
Richmond Super T-10: 2.64, 1.60, 1.23, 1.00:1
Richmond Super T-10: 2.43, 1.61, 1.23: 1.00:1
A large displacement high torque bandwidth engine in a relatively light car doesn't need more than five speeds and four properly selected ratios is fine in most cases with overall first gear multiplication of 8-9:1 unless you live at high altitude and/or hilly/mountainous country.
With an 8-9:1 overall first, a base engine will easily pull a 2.73 axle, which yields about 2750 RPM at 80 with OE revs/mile tires. SHP type engines that offer less low end torque will be comfortable with a 3.08 axle that yields about 3100 at 80.
Unless you do more than 50 percent of your driving on long freeway trips the above revs at 80 are very reasonable for a vintage engine.
Also consider that a Richmond Super T-10 runs about $2K and the Richmond five-speed is nearly double that price, heavier, and I'm not sure how you get it into a C2 with a non-removable center cross member assuming it will fit in the tunnel... I don't know.
For a deeper dive download my gear chart Excel program referenced in post #3 and play some games.
Duke
T-10 wide ratio: 2.54, 1.89, 1.51, 1.00:1 (Muncie WR ratios slightly different, but essentially the same as T-10 WR)
Richmond Five-Speed: 3.28, 2.13, 1.57, 1.23, 1.00:1
Richmond Super T-10: 2.88, 1.91, 1.33. 1.00:1
Richmond Super T-10 : 2.64, 1.75, 1.34, 1.00:1
Richmond Super T-10: 2.64, 1.60, 1.23, 1.00:1
Richmond Super T-10: 2.43, 1.61, 1.23: 1.00:1
A large displacement high torque bandwidth engine in a relatively light car doesn't need more than five speeds and four properly selected ratios is fine in most cases with overall first gear multiplication of 8-9:1 unless you live at high altitude and/or hilly/mountainous country.
With an 8-9:1 overall first, a base engine will easily pull a 2.73 axle, which yields about 2750 RPM at 80 with OE revs/mile tires. SHP type engines that offer less low end torque will be comfortable with a 3.08 axle that yields about 3100 at 80.
Unless you do more than 50 percent of your driving on long freeway trips the above revs at 80 are very reasonable for a vintage engine.
Also consider that a Richmond Super T-10 runs about $2K and the Richmond five-speed is nearly double that price, heavier, and I'm not sure how you get it into a C2 with a non-removable center cross member assuming it will fit in the tunnel... I don't know.
For a deeper dive download my gear chart Excel program referenced in post #3 and play some games.
Duke
10-13-2021, 02:02 PM
#11
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IMO it seems like everybody wants to spend a lot of money for very little gain OR bragging rights that they have a 5 plus speeds.
Do the math on ALL of this regarding miles driven at high RPMs, gas mileage, engine wear and how long you are going to live or own the car. I am betting that in 99% of cases you can’t make any economic sense out of ALL the advantages combined.
Personally I LOVE the feeling of the low end grunt of 3.70 or lower gears, will no longer be doing any more than a maximum of 2 hours highway cruises (85 mph) at a time AND I don’t buy high performance cars with gas mileage in mind. How many members are still young enough with the expectations of owning your car long enough to make this anywhere CLOSE to making economic sense?
If I wanted an old body style with all the modern conveniences I would build a restomod and be done with it rather than half assing things.
I leave major things alone on these old cars and live with it as part of the “old car experience.” I will upgrade the stock type engine (no new gen. engines for me) and change shocks, tires, alignment and MINOR suspension changes (no catalog engineered suspension kits for me.) Engine upgrades are expensive enough but yield the biggest bang for MY buck.
Rant over. 
Do the math on ALL of this regarding miles driven at high RPMs, gas mileage, engine wear and how long you are going to live or own the car. I am betting that in 99% of cases you can’t make any economic sense out of ALL the advantages combined.
Personally I LOVE the feeling of the low end grunt of 3.70 or lower gears, will no longer be doing any more than a maximum of 2 hours highway cruises (85 mph) at a time AND I don’t buy high performance cars with gas mileage in mind. How many members are still young enough with the expectations of owning your car long enough to make this anywhere CLOSE to making economic sense?
If I wanted an old body style with all the modern conveniences I would build a restomod and be done with it rather than half assing things.
I leave major things alone on these old cars and live with it as part of the “old car experience.” I will upgrade the stock type engine (no new gen. engines for me) and change shocks, tires, alignment and MINOR suspension changes (no catalog engineered suspension kits for me.) Engine upgrades are expensive enough but yield the biggest bang for MY buck.
Rant over.
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10-13-2021, 02:18 PM
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I have done a search and turned up some real old threads (including great info from DZAUTO). My 1962 which I have owned since 1975 currently has 3.08 that I had installed back in the fuel crisis days. The car has a close ratio 4 spd and the combo has never had great take of from standing. (The engine is an LT-1). My question is: how difficult is it to change out the gear ratio? What ratio would you recommend for daily driving?
Thanks
Thanks
Jeff
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vettsplit 63 (10-13-2021)
10-13-2021, 02:25 PM
#13
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It is a simple operation that can be done in an afternoon. The third member (complete) pulls out of the rear axle housing and you can bolt in another third member with the gear ratio of your choice. The axles have to be looseded at the backing plates and pulled out a few inches, but that's it. I could probably do it in about an hour. If your 3.08 unit is a positraction, I would be interested in it.
Jeff
Jeff
Or, a little more expensive (unless your trans needs attention) would be to switch to a wide ratio trans that has a lower ratio 1st gear that will solve your dead stop take off issue. This comb is the best of both worlds for most guys with your set up.
10-13-2021, 02:29 PM
#14
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All the information above is good.
If you are serious about changing the ring and pinion in your existing rear, the 3.08, 3.36, 3.55, 3.70 ratios are DIRECT interchange gears on a 3-series posi.
And as Jeff above mentioned, your rear can be pulled out and the gears swapped. Of course, it will then need to be setup with a good tooth contact pattern and bearing preload.
BUUUUUUUUUUUUT, IF IT WERE MY CAR (and it is not), I would search around for another posi center section with the desired gear ratio---------------------AND HANG ONTO THAT 3.08---------------------just in case you decide you prefer the 3.08 for installation at a later time.
I have a 3.08 posi in the 56 behind a SB400 and wide ratio (M20) Muncie. I REALLY like that combination.
Performance from a dead stop? Well, take a look.
If you are serious about changing the ring and pinion in your existing rear, the 3.08, 3.36, 3.55, 3.70 ratios are DIRECT interchange gears on a 3-series posi.
And as Jeff above mentioned, your rear can be pulled out and the gears swapped. Of course, it will then need to be setup with a good tooth contact pattern and bearing preload.
BUUUUUUUUUUUUT, IF IT WERE MY CAR (and it is not), I would search around for another posi center section with the desired gear ratio---------------------AND HANG ONTO THAT 3.08---------------------just in case you decide you prefer the 3.08 for installation at a later time.
I have a 3.08 posi in the 56 behind a SB400 and wide ratio (M20) Muncie. I REALLY like that combination.
Performance from a dead stop? Well, take a look.
10-13-2021, 05:42 PM
#15
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10-13-2021, 08:03 PM
#16
Melting Slicks
10-13-2021, 09:02 PM
#17
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The brands are: Motive, Richmond, USA Standard, & Excel (which appears to also be Richmond). No comments on country of origin.
https://www.summitracing.com/search/...rder=Ascending
https://www.summitracing.com/search/...rder=Ascending
10-14-2021, 09:14 AM
#19
Tech Contributor
The gear price swings are from supply and origin. There are no more usa made gears, US Gear is gone, leaving what you see on Summit or from any vendor. Yukon, Richmond, Motive- all imported. Motive has limited ratios, Yukon has more but a lot are back ordered. US Gear is what everyone was using the past 20+ years. Richmond is owned by the same company that owns Motive.
Here is the final nail in the coffin
US Gear – a Meritor Industrial Products Company | Maynards
Here is the final nail in the coffin
US Gear – a Meritor Industrial Products Company | Maynards
10-14-2021, 01:00 PM
#20
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I found and downloaded SWCDUKE's spreadsheet - great tool - Thanks! It sure looks like a T-10 WR with my 3.08 would be the best of both worlds - nearly the same take off as a CR/3.70 and the top end of the CR/3.08. Problem is switching out the rear is much cheaper (and maybe easier??) than the tranny. UNLESS there is someone out there who wants to swap a WR for a CR. Anybody??