Tranny swap question.

[jmlloar]

I have a 98 GMC K1500 3door short bed. It has a 5.7 and 4L60E that exploded. It has a 241 man shift transfer.

The donor truck is a 97 GMC K2500 ext cab. It has a 6.5 turbo diesel (runs but needs overhauled)and 4L80E trans. And a 241 electric shift transfer.

The 2 questions I have are: Is the 4L80E a bolt in swap other than the output splines being larger (electric plugs same). And if that will work will the transfer input shaft fit out of the 243 transfer that is in the donor truck I have. Or is the internals in the diesel completely wrong for my truck?

Both have the removable bell housing.

[stumpuller454]

do you intend to run the deisel also?

[jmlloar]

Not interested in the diesel. Its complete but has been beat. Work truck. Mine is a loaded pleasure ride. I'll prob part it out.

[stumpuller454]

I`m gonna read my manuals i know everything will bolt together, its weather the trans mount will work or if you need to use the HD crossmember...you will have to probly purchase a flywheel that bolts to the 350 and the 4L80E, dout the 6.5s flywheel can be used...probly wrong pattern and balence...

[jmlloar]

I know the trans will bolt up. Even if it wouldnt the bellhousing could be swaped. Torque converter will be diff and will need to be swapped out for a V-8 gas one. So no need to change the flywheel. And the crossmember is the same since I will be using my 241 transfer anyway. The trans to transfer adapter is the same for both tranny's only the spline size on the tranny output/ transfer input is diff.

[stumpuller454]

the bell housing isn`t changable but not a problem, the flywheel will defiantley have to be changed or checked closely, the 4L60E has three studs on the TC and the TC for a 4L80E use 5 bolts through the flywheel, as for electrical connections it will have to be a visual comparison as i would not be surprised if its the same, the crosmmember can be re-used, it is slotted and should accept the bigger trans. i can only find a 261 manual shift and a 246 auto matic case then the borg warner model in the one tons... in the 98 c/k manual, and of course it doens`t have an "interchangability table" but maybe 75K30 knows more about the t-case swapabilties...

OH and another thing it may be neccesary to re-flash the ecm for running the 4L80 as compared to the 60, I recommend contacting someone like WESTERS GARAGE or blackbear performance, nelson performance etc, etc, to get a program made up for you, it would be a double bonus this way as they can give you a tune also for your engine to wake it up a bit!

[jmlloar]

Not if I remember correctly. The diesel is 6 bolt. And the gas was always 3 bolt. As far as I can remember gm never used 5 bolt on anything. On the transfer I'm not positive which model but it is an electric shift one. Truck is not a 1 ton. It's only 3/4 ton.
also gm used bolts. ford used studs

[jmlloar]

Both bells unbolt starting with the 96 model. Do you mean the 4L80E and 4L60E bells are diff on the tranny side?

Will the older 1 piece 4L60E swap out for the newer 2 piece one? If so how far back?

[stumpuller454]

I`ve been fooled by the rediculously small pics in the manual, i had to resort to reading, yup bolts not studs and the 4L60 bell is removable but the 80 isn`t, plus there is 6 not 5 bolts on the 80 (i counted wrong!). either way they both will bolt to the engine, so don`t worry about that.

I re-read your first post, do you have 2 donor trucks? is there something wrong with the t-case already on the 80?

[jmlloar]

I have the 2 trucks. My 98 and the 97 diesel.

I dont want the crappy electric shift t case thats in the 97. I like the good old shift lever in my truck.

The 98 is my truck. Its an SLE that is loaded.
The 97 diesel is the parts truck. Plain jane no extras.