is this tranny swap possible

my 1991 buick lesabre custom's transmission is completely shot... wont shift from 1st to 2nd and slips in 3rd...

my car is a

1991 buick Lesabre custom 3800
VIN = 1G4HP54C1MH425195


my friend has a

1994 buick Regal custom with a locked up TPI 3800
VIN = 2G4WB15L7RI427198


her tranny is still good and shifting fine.... mine is not.... i was looking online supposedly mine has the 4T60 and hers has the 4T60-E....

though my 91 does not look the same as other 91's and does not have the same gauge cluster... i looked and her tranny has the same things on the front side...

will this be possible... is the tranny from this regal compatible with my lesabre custom?

a guy at a transmission place told me if it has the same amount of pins in the connector that it is compatible as i read and keep reading that my car is the newer 1991 model and was made past May and has the 4T60-E

My experience with that particular era is limited but I did recently rebuild and upgrade a 4t65e on my 2000 LeSabre. I'm going to go out on a limb and say the chances are pretty slim. The best advice I can give you is to get the ATSG rebuild manuals at www.atsg.com. I have the one for the 4t60-e which I'll sift through later to see if it mentions anything about the 1991/1992 transition.

You're going to face many many challenges trying to find a proper match for any of the 4t60/65 transmissions. Even within the same model year there are usually upwards of 10 different variations of the same transmission. Amongst LeSabres within the same model year there are at least two varients of the 4t60/65e used throughout the 90's and 00's. LeSabre had an option from 1992 to 2005 which upgraded to a 3.05 final drive ratio. The 3.05 unit came as part of the Gran Touring package. Everything from sprocket ratios, to torque converter and final drive ratios are specific to your vehicle. Changes in any of those specs with a swap will thoroughly confuse the PCM. Even minor changes in solenoids and valves will throw the PCM out of wack because it will be calibrated for the precise configuration installed in your car. When you buy an aftermarket rebuilt transmission they take great care to match all of those specification to your specific VIN and transmission service tag.

You can typically purchase a cheapo rebuilt trans for less than 1k online. You might also want to ask a local trans shop what it would cost to rebuild yours if you do the labor of removing and reinstalling it yourself. You can also buy the rebuild manuals from ATSG and take a stab at doing your own rebuild to solve the problem you have.

This swap will not be possible..

Your 91 has the 5 pin connector and is not controlled by the ECM, with the exception of the TCC clutch..


The 94 has the 4T60-E that is controlled by the PCM..

You would have to wire in the harness and the newer PCM to make it all work..

So the trans you are looking at will not work for you..

All of the H bodies used the THM440-T4( 4T60 ) for the 91 models... The 91 C Bodies went to the newer 3800 TPI engine and 4T60-E trans..

ATSG offers update and service manuals for the 440-T4 as well as the 4T60E. All of the manuals are relatively cheap and would provide you with a lot of great information if you are looking for a donor unit. You could also get an idea of what's wrong with your current transmission.

When you perform your swap you have to pay close attention to the metal transmission service tag attached to the tranny itself. The ATSG manuals help you decode the service tag and tell you how to match specs on your donor unit.

I really don't think that re-wiring or somehow superficially "hooking up" the later model transmission will result in any sort of success. The PCM is calibrated very carefully to match all of the little nuances in the valve body design. You really need a transaxle which is mechanically and electronically identical to yours.

Even late model 4T65E units with identical mechanical specs and identical electrical connectors underwent major design changes internally that would render seemingly identical units entirely incompatable and useless for swapping.

You have to understand all the internal design changes and specifications from one model years to the next before you attempt any sort of swap.

Pcmos's post is excellent.

Think of GM's eras as distinctly cutting off in 1991 and starting over in 1992, then starting over again in 2000. Major swaps generally won't cross these boundries (there are exceptions like the 91 Park Avenue, which is almost a clone of a 92 Lesabre.) The ATSG book for my 92 Lesabre's tranny was excellent and educated me that I could use the innards (including valve body area) from a 94 Lesabre tranny (which I happened to have) for rebuilding my 92 Lesabre's tranny (which I did.) I simply used the internal wiring harness from my 92, checked to see that the gear ratios matched (which they did) and installed a shift kit (which was very good.)