Turbo 400 to 4l80e swap in a suburban

[Newman7786]

Good morning all. Well I believe that the turbo 400 in my suburban has gone out. I was driving it on Friday night when an awful tick/clunking noise started. It went away after a few minutes of driving but then the trans started slipping. Parked it at my stop and then when I went to go home it was a very harsh engagement at first and then barely made it home. Fluid level is up where it needs to be and cannot see any leaks. Tried to drive it to a friends shop yesterday and it wont move at all. The engine revs up but I don't feel the trans engage when moving the shifter. I will be getting it on a trailer tomorrow and getting it to the shop for triage.

Looking around yesterday I found a guy selling a 1991 3/4 4x4 suburban with a 6.2/4l80e combo. Body is rusted away but it has a plow and starts and drives great. I know 91 was the first year for the 4l80e and having it be in a square body suburban is rare. I am looking to swap the trans and transfer case into mine to gain the overdrive. With my research I will need the drive shafts as well because the 4l80e is longer than the 400. The torque converter will have to be changed as well going from a diesel to gas.

Looking for an other small things to look out for when doing this swap as I know there is a TPS and VSS sensors that have to be accounted for. What about shift linkages? Independent controller for the trans?

TIA for all the answers and I will let you know if it is a quick fix on my trans or if I will be going headlong into the swap.

 

[yevgenievich]

Use the ecm from the 91 diesel. It is already stand alone. Tps needs to be transferred

 

[RoryH19]

You've covered all the items. As @yevgenievich mentioned try to use the controller from the 91.
You should be set.
And yes, rare to find a 4L80e in a square.

 

[Newman7786]

Thanks for the replies and the reassurance guys. Researching some more and found some conflicting info on the speedometer. Will I have to take the one from the donor vehicle or will my existing one work?

 

[yevgenievich]

Thanks for the replies and the reassurance guys. Researching some more and found some conflicting info on the speedometer. Will I have to take the one from the donor vehicle or will my existing one work?

If going with vss spedo and not doing some conversion then donor spedo. Need the buffer box as well

 

[Newman7786]

Thank you. I will be going to look at it on Saturday and see if it is coming back with me or not.

 

[Newman7786]

Well I went and looked at the 91 suburban and it was not as advertised. The gentleman claimed that the trans was rebuilt but didn't have any paperwork and couldn't remember when. We could not come to an agreement on a price so I moved on.
In the mean time I was able to pull my trans down. When I drained the pan the fluid did not look dirty and the magnet did not have much for metal particles on it. There was also a missing bolt on the bellhousing on the passenger side. Not sure if I found the problem but this is what my flexplate looked like. I have never seen this before and I was surprised that the truck still started. What is the opinion here on whether or not I should have the transmission gone through? Just put up a flex plate and see what happens?
Thanks

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[TubeTruck]

Holy cow!!! I would blame brittle metal. If it were me I would throw a new flexplate on and hope it doesn't break again. You're engine obviously spins well enough for the flexplate to catch and start but not enough to engage the transmission. What does your harmonic balancer look like?

 

[Rusty Nail]

Yep!

That's your trouble lol and totally badass, btw.

Spare the tow, save your money and get to work Big Boy!

 

[eskimomann209]

Note to self.
Awful(Click+Clunking)=fubar flex plate.