: Changing final gear ratio



eldorado1
05-14-04, 01:45 PM
I apologize if this is in the wrong section - but I couldn't find any tranny-specific one... Anywho, how much work is it to change the gears from a 3.11 tranny to 3.73 gears?

4t80e sorry..

BeelzeBob
05-17-04, 12:11 AM
I apologize if this is in the wrong section - but I couldn't find any tranny-specific one... Anywho, how much work is it to change the gears from a 3.11 tranny to 3.73 gears?

4t80e sorry..
It isn't the simplest nor easiest job but it is possible to remove the complete final drive assembly from the trans while the trans is in the car. The tail housing of the trans comes off after removing the wheel/tire, knuckle, drive axle, etc... then the final drive can be removed and replaced.

If you replace the existing final drive with a 3.71 ratio the PCM cal that you have will not recognize this and will set some codes as it will think the trans is incorrect.....

eldorado1
04-16-05, 05:27 PM
I'm right in the middle of the swap. How in the **** do I remove the HUGE snap ring holding in the large gear? The one that's 8" in diameter, and 1/4" thick!?! I assume I need to compress it somehow to remove it from the grooev, but with what!?!

eldorado1
04-16-05, 06:43 PM
Nevermind, figured it out. What a pain that stupid snap ring was...

sts15l7
04-16-05, 07:59 PM
damn. that seems like a hardass job eldorado1, to be doing urself at least.

good luck, and be careful! :)

eldorado1
04-16-05, 08:24 PM
Naw, it's not so bad. Sucks to have a time restraint though (gotta be done by monday) http://cadillacforums.com/forums/images/smilies/16suspect1.gif

Ran into a couple problems, but when in doubt, use a BFH. http://cadillacforums.com/forums/images/smilies/bouncy.gif

eldorado1
04-17-05, 08:32 PM
w00t! No leaks, and it runs pretty good! All the cars should have 3.71 gears :D

Hason560
04-18-05, 01:59 AM
what about the codes? did you get any? i know you are into something very custom so i have no idea if you even useing the stock computer.

eldorado1
04-18-05, 02:43 PM
what about the codes? did you get any? i know you are into something very custom so i have no idea if you even useing the stock computer.

hehe nope - my computer thinks I'm running a manual ;)

davesdeville
04-18-05, 08:33 PM
...thinks you're running a manual? Aren't shifts controlled by the PCM in these cars?

eldorado1
04-18-05, 10:35 PM
...thinks you're running a manual? Aren't shifts controlled by the PCM in these cars?

Yes - I built my own f1-style-paddle-shifting TCM to control the transmission.

mtflight
04-18-05, 11:19 PM
holy smokes, that sounds cool! How did you do that? Show it off by posting some pictures.

eldorado1
04-19-05, 12:55 AM
holy smokes, that sounds cool! How did you do that? Show it off by posting some pictures.

How did I do it? I'm an EE, I build electronic gadgets ;)

It's not much to look at...... I'll be selling these on ebay and elsewhere if you're interested....... http://cadillacforums.com/forums/images/smilies/drinker.gif

mtflight
04-19-05, 12:48 PM
Very cool... all you need now is a racing seat with lateral support, and a helmet!

duecentoi
04-23-05, 03:20 AM
How do you get the PCM to still control line TV (for lack of a better term) pressure when taking shift control away from it? It will set a code if it isn't in the gear the PCM wants, after all. How much do you want for the paddle shift set up? Email me at flatboy@comcast.net, if you would.

eldorado1
04-23-05, 01:53 PM
For anyone else that was interested - the pressure is controlled by tying into the throttle position sensor. Wide-open-throttle is max pressure (adjustable by you), idle is min pressure (again, adjustable). OBDI computers can be rechipped into thinking they're running a manual, and then don't care about what gear they're in. For pricing, determine your own. They'll be on ebay soon http://cadillacforums.com/forums/images/smilies/thumbsup.gif

MrEr1c
04-25-05, 12:16 PM
the manual paddle shifting sounds cool with a caddy but what year will you be making them for? only the obd1 cars?

how does the car run with the new gears? feel quicker? have you brought it to the dragstrip with the new gears yet?

DeVillish
04-25-05, 04:44 PM
omg that is the coolest freaking thing i've seen for a caddy so far! I would love to have a paddle shift caddy, so cool! do you still use the stock shifter to put it into drive and park and stuff? kinda sounds like a dumb question but i dont really know to much about paddle shift cars. thats soo cool though. i'll be very interseted in getting that if the price is right(and if i even get the eldorado i want, its a 93 so obd-1 yay).

eldorado1
04-25-05, 05:05 PM
the manual paddle shifting sounds cool with a caddy but what year will you be making them for? only the obd1 cars?

how does the car run with the new gears? feel quicker? have you brought it to the dragstrip with the new gears yet?

It works for all cars with the 4t80e transmission (i.e. every northstar caddy, olds 4.0 aurora, etc..) Development for the 4t65e is coming soon, and 4t60e after that. Please note that this isn't specifically designed for the caddy, but more of a "hot rodder toy". You may have to putz around with making the computer happy when using it with the stock car. Or custom rig the paddles to work well with the caddy steering wheel.

Back on topic - the car runs great with the new gears. It feels quicker from a stop and in mid-throttle, but overall, the butt-dyno says it feels about the same... I have not brought it to the dragstrip (either before or after).

ronbo
07-05-06, 05:27 AM
eldorado1, can you PM me... again?
(it's been quite a while, but I dtill don't have PM privlages)

re: TCM - I know you stopped making yours, but I'm getting desperate - and about to dig into my old prototyping parts... see what MCU I can come up with to do the job... but I want to explore all other options first - which is why I'm looking you up again. (I have over 25 yrs in EE / R&D, but not active in my current job - though it's still my main hobby... besides my car)

My ride:
'98 Aurora Autobahn, immaculate White Diamond, 80k miles, med. dark. tint all around.

I've looked at the Granetelli Trans Tuner (in fact, have one in transit), but really don't like the idea of running higher line pressure full-time, when it's only needed during heavy throttle application (or actually just during the shift, if that's predictable from various inputs far enough in advance to affect line pressure before the shift actually happens). Would also like manual control over the shifts - ala: paddle-shift, but maybe not using paddles.

My mod list:
Full intake box mods (no more restrictions there, also using Accel Kool Blue filter element).

Exhaust: using latest St.Steel. high-flow metallic element 300 cell core cat. converter, straight thru S.S. resonator, S.S. mandrel-bent pipes back to S.S. Borla XS muffers, dual oval S.S. tips.

Just finished: Cross-drilled (& chamfered), Slotted, Anodized (silver), Deep-Cryogenic treated rotors; P.F.C. Carbon-metallic pads (Deep Cryo treated); epoxy painted (white) calipers.

Also (this week) 18" rims (Boss 318's), 255R4518 all around (leaning towards Kumho ECSTA ASX W-rated tires, nice 420 treadwear rating - new silica compound)

Next up is boring my T.B. and spacer out to 80mm.
Then I'll be looking for ways to move the torque curve up a bit, and relax that redline to maybe 6500.

Also like the idea of the new electronic power steering pumps - get that load off my engine! PRobably would call for more CPU work to control it... unless there's a good donor solution.

ANYWAY... I'm already at the point of worrying about my trans. clutches - since the factory programming allows for such a sloppy shift.

So far, for not having touched the engine internals, the ECU or TCU, I'm amazed at how much better this 4.0 runs... why did they suffocate it so bad?? I often wonder if the 4.0 responds better to mods than the 4.6l does for some reason. (and I can still average 21+ MPG)

Any help would be greatly appreciated!

zonie77
07-05-06, 12:13 PM
Give us a complete run down. We hear some predictions of codes and not running but I think it should run great. Shift points might be off but maybe not.

I had said it might be a great mod for city/suburban driving.

Anyway, gas mileage change, performance, shift points, highway cruise, I'm interested.

parts68
07-06-06, 08:11 PM
Ive got a spare 371 tranny if you need it

0to60n4.5
07-06-06, 09:57 PM
Project sounds like fun, but I'm glad my 01' STS has 3.70 gearing and a gated shifter.