GT Trans on an SE

[Burton99SE]

Any one here replaced their SE trans with a GT or GT1 and kept the same SE computer(engine size 3.4L)?
I found two threads here.
One say it will work and another says it wont.

I just want to make sure it does, before I spend $600 to find out that it wont work?

Thanks

[Brandon]

gt/gt1 is the same tranny :)

[Colin]

Originally posted by Burton99SE
Any one here replaced their SE trans with a GT or GT1 and kept the same SE computer(engine size 3.4L)?
I found two threads here.
One say it will work and another says it wont.

I just want to make sure it does, before I spend $600 to find out that it wont work?

Thanks The GT has different gearing therefore the computer has a different program ...

[Burton99SE]

So if I get the GT computer to work with the GT trans, will the SE engine wiring match up with the GT computer?

Originally posted by Colin
The GT has different gearing therefore the computer has a different program ...

[MantaGreen97]

Yeah the final drive is different, plus I *think* the GTs had a 4T45-E instead of the 4T40-E to handle the whole 10lbs ft. more torque or whatever :roll2: lol.

The transmission out of a GT should work with the SE's PCM however it might not behave as it would in a GT (with a GT PCM) because shift points might be different. I believe the 40 transmission has a higher maximum shift speed than the 45 does, however it's only be a couple hundred RPM IIRC.

I wonder, then, if the GT transmission will perform better with the SE PCM, at the cost of transmission longevity though?

[RickHigginsHtbr]

i forget where i read it, but a company is making the gearing to turn a 4t40e into a 4t45e. but yea, the 4t45e may handle 10 extra lbs of tourque, but i know my eco redlines at 6700 - 6800 rpms, where the 4t45e won't rev that high. get the gear kit, and while your in there, do the LSD kit too :) more work, but a little less money (maybe) and definately better results.

[TA^Guy]

Originally posted by RickHigginsHtbr
i forget where i read it, but a company is making the gearing to turn a 4t40e into a 4t45e. but yea, the 4t45e may handle 10 extra lbs of tourque, but i know my eco redlines at 6700 - 6800 rpms, where the 4t45e won't rev that high. get the gear kit, and while your in there, do the LSD kit too :) more work, but a little less money (maybe) and definately better results.
Your telling me that a 4T40E will turn greater RPMs than a 4T45E?
They are essentially the same exact transmission.
Thats like saying because I swap my differental gearing in my truck from a 3.43:1 to a 3.73:1 that my truck won't rev to 6500rpm anymore. It will, however your speed at said RPMs will change.

[RickHigginsHtbr]

Originally posted by TA^Guy
Your telling me that a 4T40E will turn greater RPMs than a 4T45E?
They are essentially the same exact transmission.
Thats like saying because I swap my differental gearing in my truck from a 3.43:1 to a 3.73:1 that my truck won't rev to 6500rpm anymore. It will, however your speed at said RPMs will change.

wow, now that i read what i wrote, i feel like an idiot :lol: keep forgeting the different engine thing.

[car audio dave]

a GT computer should work on the 3400 as long as its from the same year. i dont think the engine was any different except for the "ram air" and "dual" exhaust. none of that is effected by the computer anyway.

[Patchez]

Toss in the trans and get the VCM flashed with the same year GT information. GOOD TO GO!!

[99blackSE]

It would probably be cheaper and easier as said before to just change the gears and do some other parts to it.

[bu01]

FYI

the grand am se has the 4t45e with the 3.05 ratio
the grand am gt has the 4t45e with the 3.29 ratio

the malibu has the 4t40e with the 3.05 ratio

the alero has the 3.05 ratio but i forget if it has the 40e or the 45e

[Colin]

FYI , the SE has the 4T40E with 3.05 ratio and the 4T45E is optional ...

[gectek]

ok well to start out all transmissions are not created equal. the 4t40 "can handle" alot more revs, because it has the 3.05 gearing, that means that for any given MPH it will have lower RPM than the lower geared 3.29. simple gear ratio concept. ok so then why is the 4t45 rated to hold more power, just a few changes with internal bearings really and a few upgraded parts. GM always goes conservative with their numbers of course. also, the sensors are the same and the FDR is given to the computer via the output shaft speed sensor, so there is no need to change the computer to compensate for gear ratio changes, because the differential is IN the transmission. only on a RWD would u need to do that. the only changes in the 4t40 programming that i could think of would be the shift pressures, and the TCC lockup and a few other things, but it could run just fine if you used the DHP PT on it. any other trans questions?

also you dont have to have gearing to run a 4t40 in a 45, they are different final drives, so just swap out the ring gear, final drive carrier and the sun gear and thats it. 3.29 in a 4t40. but also you can change the chain drive ratio in both of them to garner different FDR as well. the regular ratio is 35/35, but you can get 33/37 or 32/38...so that means u can get up to a 3.91 FDR with the 32/38 chain drive and 3.29 gear ratio...talk about fun. im building my trans with that right now, so i will let u in on that when i run it at the track

[TA^Guy]

Originally posted by RickHigginsHtbr
wow, now that i read what i wrote, i feel like an idiot :lol: keep forgeting the different engine thing.
lol, no need to feel like a idoit, crap slips our minds from time to time. :D
Originally posted by 99blackSE
It would probably be cheaper and easier as said before to just change the gears and do some other parts to it.
He may not be looking just for the incressed gear ratio, maybe he is getting a new transmission because his is shot. In that case you are looking at a near minimum of $1000 for a rebuild. I wouldn't say it's easier nor cheeper.
Originally posted by gectek
ok well to start out all transmissions are not created equal. the 4t40 "can handle" alot more revs, because it has the 3.05 gearing, that means that for any given MPH it will have lower RPM than the lower geared 3.29. simple gear ratio concept.
Correct, technically the RPMs are teh same, just with a lower ratio the speed will be incressed slightly to each rpms.

3.05 to 3.29 really is not that large of a difference.

I would look at what the car is being used for before I start swapping.

Mostly highway driving I would keep the 3.05:1. Better fuel ecconomy and higher topspeeds (if it were unrestricted).

City driving or some weekend drag racing, the 3.29:1 obviously gives you a edge off the line and in traffic doesn't require the motor to work as hard to get the vehicle moving for stop light to stop light.

[gectek]

well u cannot really say that the 3.05 is better for highway driving though, due to a number of factors, it has been proven many times that changing the gear ratio doesnt always mean you take a loss on the MPG...with my 3.29 i used to get about 30 or so on the highway, now 3.91 thats a different story

and any change in gear ratio can be a big difference due to torque multiplication and output/input speed. if you have the OD gear lets look at that. it is .68 correct. so that is the gear is driven .68 times faster than the direct gear, so that is on the 3.05 od = 2.07, on the 3.29 its 2.24, so that is a small change, but in the gearing world it is alot of change, just like the OD in a RWD goes like this on the 4l60 the ratio in 4th is .70, with the stock gearing in a z28(which is 3.42FDR) that is 2.39, with the 3.73 it is 2.61 for the overall gear ratio. so even with a small change in FDR, it gives a big performance in overall ratio in any gear

[TA^Guy]

Originally posted by gectek
well u cannot really say that the 3.05 is better for highway driving though, due to a number of factors, it has been proven many times that changing the gear ratio doesnt always mean you take a loss on the MPG...with my 3.29 i used to get about 30 or so on the highway, now 3.91 thats a different story
Technically if all other factors are the same average highway fuel consumption will be reduced, but as I stated it is only a slight difference.

Same principles apply to FWD, RWD, motorcycle, ect.

[gectek]

unless by changing the ratio you keep the engine better in its power band helping the timing and everything else take better advantage of the gears...yes obviously since u pull more RPM per MPH it seems like u should get worse MPG, but that is not always true...it has to do with lockup, and a few other things, like i mentioned the powerband and other variables

i thought that switching to higher gears from 3.42 to 3.08 in my 95 blazer that i would get better MPG...i was wrong

[TA^Guy]

As for Blazers with lower ratios they are horrible and suck more fuel around town than with 3.43:1 Driving my 4.3 with 3.43:1 LSD and going to my fathers or Friend's blazers with the lower ratios they are exteremly doggish espeically with larger tires. That can have a dramtic effect on fuel consumption.
After all some 73% of a average fuel consuption is from accelerating from a stop.

[gectek]

esp at WOT...lol

im lookin at making that one a cyclone anyway hopefully

[mikethomas]

Bottom Line: For 600 bucks you could do better. The gearing differences are not worth it for a 175hp car. If your plans are for more power. I would find a way to improve the chain of the 4T-45E trans. That in my opinion is the weak link of it all. Or, do as GM did and modify the 4T-65E of the Grand Prix with a custom 1/2 shaft and benefit from higher power ratings in that you can put much more power to the 65.

[gectek]

the chain is def not the weak link, they upgraded it from 3/4 to 7/8 in 98 or 99 IIRC, and the gearing is alot better for lower end perf. the 4t6x swap is alot more invovled than just getting one and slapping it in. the only weak link in the 4t4x trans are the plastic accumulator pistons, and if it is a 99 - 01 trans then the crossdrilled valve needs to be replaced with a new solid one. im going to run 3.91 gears in my GA in a few weeks, and that is going to be fun.

[CARS GONE WILD]

hold on, so having a taller gear to reduce rpms will not reduce mpg? well what about when you're at highway speeds at lets say 3k rpms, if you had taller gearing so that you'd be going the same speed in mph but at 1500 rpms or so, wouldn't you be consuming less? can the motor really be injecting the same amount of fuel at 3k or at 1.5k ? logically mpg should get waaay better, right?

[CARS GONE WILD]

also, is there some way to alter only the 4th gear, as in make it taller or replace it with another so its good for highway crusin, but leave the other gears alone? i dont know much about auto trannys...or manual for that matter...but can anyone here share info or opinions?

[grandam01]

Ahhh gectek getting out with the tranny knowledge, I believe the discussion has been set before about our tranny's, there is an ongoing debate about the weak links in the 4t4X tranny's gectek seems to be the only other person person testing it out at the track, I still have to try and get in on one of the tranny builds from ya gec.

[gectek]

thanks man ill give everyone the heads up soon

[9t8alti]

I have a GT 4t45-e in my SE with no computer change and it drives ok but it does shift hard after driving for a while or pushing the car hard the trans seems fine because i can turn the car off then start it back up and the trans shift smooth as butter againand the trans fluid is still bright red, this only happens once and a while.

[GrandAm2000se]

they are basically the same trannys, and they all SUCK