Rear gearing?
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Burning Brakes
Joined: Jun 2005
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From: Hyde Park NY
St. Jude Donor '05
Rear gearing?
I have a 95 VERT, stock 3.07 rear differential. What are the options and associated advantages/disadvantages of changing the rear gear ratios. Any info would be appreciated.
Team Owner
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From: Athens AL
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On an LT1 you'd get at least .2-.3 if not more (depends on driving skill) in the 1/4mi, it'll feel like a whole new engine.
Downside would be mileage losses on the hwy, but 3.54 should be a nice choice and not cost you more than a couple mpg on the hwy at most.
If the mpg losses scare you away, a torque converter would give about the same gain in ET, but no loss of mileage.
Downside would be mileage losses on the hwy, but 3.54 should be a nice choice and not cost you more than a couple mpg on the hwy at most.
If the mpg losses scare you away, a torque converter would give about the same gain in ET, but no loss of mileage.
Instructor
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From: fl
IMO, For an automatic, a 3.73 is about perfect..the acceleration difference from what you have now is really not describable(it's that drastic)....Like was mentioned, a bit less gas mileage on the highway, but about the same around town, Iv'e had some cars that actually got better mileage with (stop and go driving) after the gear..........with an otherwise stock car , with dragradials so that you would have some traction, you could drop over a half second from your quartermile times(seen it so many times)......and even more of a gain with the right converter selection...(with traction)....
Last edited by 95NOSvette; May 10, 2006 at 01:23 PM.
Instructor
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From: fl
Originally Posted by RAGOVET
OK. One question .. Assuming my 3.07 stock differential is a D36 and to go to the 3.54 or 3.73 would need the D44, do i also need a different drive shaft?
Last edited by 95NOSvette; May 10, 2006 at 02:28 PM.
Team Owner
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From: Athens AL
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Originally Posted by RAGOVET
OK. One question .. Assuming my 3.07 stock differential is a D36 and to go to the 3.54 or 3.73 would need the D44, do i also need a different drive shaft?
You dont need a new driveshaft.
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Team Owner
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
If you drag race, pick a ratio that will put you at the top of your 1:1 gear in the quarter mile. (auto = 3rd, stick = 4th).
If you are concerned about highway cruising and mpg, pick a ratio that'll give you an acceptable rpm in overdrive at the speeds you drive.
If you are concerned about highway cruising and mpg, pick a ratio that'll give you an acceptable rpm in overdrive at the speeds you drive.
Thread Starter
Burning Brakes
Joined: Jun 2005
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From: Hyde Park NY
St. Jude Donor '05
Originally Posted by CentralCoaster
If you drag race, pick a ratio that will put you at the top of your 1:1 gear in the quarter mile. (auto = 3rd, stick = 4th).
If you are concerned about highway cruising and mpg, pick a ratio that'll give you an acceptable rpm in overdrive at the speeds you drive.
If you are concerned about highway cruising and mpg, pick a ratio that'll give you an acceptable rpm in overdrive at the speeds you drive.
Interesting. I assume that the increase in RPM that I would run at , if I were to increase my rear gear ratio, would be portional to the ratio of the new gear to old??? In other words , if I go with a 3.54 rear gear, then the increase in RPM I would see would be 3.54/3.07 or a 15% increase. If this correct? Anyone know...? If I went with 3.73, it would be a 21% increase in RPM? I believe that at 70 mph in OD, I run at about 2000 rpm, so this would increase to 2200 for 3.54 and 2400 for 3.73. Is this proper interpretation?
Thread Starter
Burning Brakes
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From: Hyde Park NY
St. Jude Donor '05
In addition to the question on RPM/MPH vs rear gear, I have a question on changing the rear gear and the computer control module for the A4 transmission shifting. Does changing from my stock 3.07 rear gear to a higher gear, require that I change the computer programming to reflect this for transmission automatic shift points???
Melting Slicks
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From: Milan
Originally Posted by RAGOVET
In addition to the question on RPM/MPH vs rear gear, I have a question on changing the rear gear and the computer control module for the A4 transmission shifting. Does changing from my stock 3.07 rear gear to a higher gear, require that I change the computer programming to reflect this for transmission automatic shift points???
same rpm.
different speed.
If you adapt the speado gears (to read the new correct speed) you will have the TC lockup at part throtte coming later if you see the rpm and at the same speed as before.
If it was using to lock at say 1800 rpm at 45 mph... now it will be at 45 mph at 2200.
(I used random speed and rpm for the example....)
-Beppe-
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Something like that.
Or calculate it. Pick 26" for tire diameter if you don't know any better.
MPH = RPM x TireDiameter / TrannyGear / RearEndGear / 336
RPM = MPH / TireDiameter x TrannyGear x RearEndGear x 336
Or calculate it. Pick 26" for tire diameter if you don't know any better.
MPH = RPM x TireDiameter / TrannyGear / RearEndGear / 336
RPM = MPH / TireDiameter x TrannyGear x RearEndGear x 336
Melting Slicks
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From: Lakeville MI
With a 4L60E, shift points are set as a function of tps and mph for each gear. (At least that's how my 95 K1500 with pcm 0D works.)
The shift points will need to be reprogrammed to occur at lower speeds to maintain the desired shift rpm. You can scale the tables by the old ratio/new ratio.
The shift points will need to be reprogrammed to occur at lower speeds to maintain the desired shift rpm. You can scale the tables by the old ratio/new ratio.
Instructor
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From: fl
Originally Posted by tequilaboy
With a 4L60E, shift points are set as a function of tps and mph for each gear. (At least that's how my 95 K1500 with pcm 0D works.)
The shift points will need to be reprogrammed to occur at lower speeds to maintain the desired shift rpm. You can scale the tables by the old ratio/new ratio.
The shift points will need to be reprogrammed to occur at lower speeds to maintain the desired shift rpm. You can scale the tables by the old ratio/new ratio.
Last edited by 95NOSvette; May 11, 2006 at 02:06 PM.
Thread Starter
Burning Brakes
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From: Hyde Park NY
St. Jude Donor '05
Originally Posted by 95NOSvette
Part throttle yes.......but full throttle goes by engine RPM
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Originally Posted by RAGOVET
OK for a 1995 A4, if I were to get the new 3.54 or 3.73 gears for my D36 (replacing the stock 3.07) what do I need to reprogram the computer??
Thread Starter
Burning Brakes
Joined: Jun 2005
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From: Hyde Park NY
St. Jude Donor '05
Originally Posted by vader86
You dont have to upgrade to D44, they make the 3.54/3.73 for yur D36.
You dont need a new driveshaft.
You dont need a new driveshaft.
I am told that they do NOT make the 3.54 or 3.73 for the 3.07 D36 carrier but only for the 2.73 D36 carrier???
Le Mans Master
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From: Metairie Louisiana
I also want to know how this works out. I have the same gear 3.07 with an auto trans. The difference is that I have a 2800 stall Torque converter and have a problem now getting traction on the launch. I know this would be solved if I got stickier tires but it's a daily driver and I have no way to store or get extra tires to the track which is 1.5 hours away. I wont give up my tires good wet traction. It's saved my *** too many times. 
Thanks
