1991 Suburban 2500 4x4 Turbo 400 to 4L80e

[cjk3500]

Hi,

I'm looking at a really nice 91 2500 4x4 with a 350.  It's fully loaded with everything but the 4L80e.  What would I need to swap in a 4L80e in place of the Th400?  I already have a chip for a 91 with the 350 and 4L80e.  I know that 91 was the only year you could get the 80e.  I think the Tcase will bolt to the 80e but I might have to move the cross member and change the lengths of the drive shafts.  That doesn't bother me.  I always looks for 91s and I really love this one and was ready to jump on it until I looked at the gear shift indicator and didn't see the D with the circle around it    I was also thinking about eventually swapping in a 6.2 LS motor and 6L90e but that will probably be quite a while when the prices come down.  I'd love to be able to bolt in a 4L80e to hold me over.  I hate a Th400 and 4.10s on the highway not to mention the gas bill 

Thanks for any help or ideas!

[slammed79]

A gear vendors unit would prolly be the easiest lwau to go until your swap, then only the rear shaft will need to be shortened. Just my 2¢

[cjk3500]

Yeah, I was thinking about the GV.  Then after I swap to an LS motor I could use the GV on something else.  The Th400 in this one is in great shape.  Supposedly the PO changed the trans fluid every time he changed the oil    Either he almost never changed the oil or he spent a ton of money on trans fluid 

[slammed79]

Yeah, I was thinking about the GV.  Then after I swap to an LS motor I could use the GV on something else. 

Exactly!  It keeps the cycle of building projects goin. Plus you'll have an engine and trans on hand to start the next one with

[cjk3500]

Yeah, I just have to find a deal on a GV with the right adapter...  I have plenty of driveshafts I can shorten..

If I can find a cheap enough 4L80e I could get a stand alone controller for about half of what the GV would cost.

[Lt.Del]

since 4l80e came in these 91 2500's, go to a salvage yard and get parts off of one.  You may have to ask around at several yards or wait a bit.  I know th 2500's were not as common at the 1/2 tons.

www.delbridge.net/suburban.html
 

[cjk3500]

Thanks for the reply!  Your Suburban is really nice!  What kind of MPG do you get?  My 91 2wd 454 with the 4L80e only gets about 12...

[Lt.Del]

thanks.  you mean gallons per mile?  I get around 10-11 in the city, which is most of my driving.  I have gotten 18 on the interstate once, all interstate going to the outerbanks of N.C. and following a tractor trailer a lot of the way drafting.  I can usually get around 16 on the highway.  I have 3.73 gears and ran 33's most of the time.  I am going down on the tire size to 265 75 16's and that will give it a tad more gear down low.