Transmission swap

[dmbaile]

Alright, I've got a '98 K1500 with the 5.7L. I've got a BBK throttle body, Comp Cam, K&N filter, and dual exhaust on her. I've only got about 117K miles on her, but I'm going to have to replace the transmission relatively soon. It's starting to act up and I've heard that it's expected to go out around 100K. I've got the Z71 4-speed automatic transmission, but I was thinking of trying to put a 5-speed automatic in her. The problem is I don't know anything about the problems that might arise. I don't know how much of a role the computer plays in that and I don't know any engine light that would come on. I know there will be problems with the shifter and the numbers on the instrument panel, but I don't know what. If ya'll have any info/thoughts/ideas on this please let me know.

[Koots]

I don't think there is a 5 speed auto that could be easily installed into the chassis and mate with the engine. If you have the cash you could probably go with the new 6 speed auto's but there is a lot of hurdles to get over in that department as well.

The transmission needs a computer to control it and i don't think the aftermarket has one yet and it's not economically feasible (not impossible though) because the price of the new transmission by itself could probably get you an LS1 and a 6 speed manual (just guessing)

Thats all the info i can give you, sorry if it doesn't help and Welcome to the site :fsc:

[dmbaile]

Thanks for the welcome.

Are you talking about the Allison thats in the new Chevy's? Would that really work? What kind of computer issues would I have?

[98GreenMachine]

GM doesn't have a 5 speed auto in any of its vehicles. Majority are the 4 speeds and the Allison is a 6.


I think there already was a thread or two about trying to fit a Allison in a OBS, the conclusion being it ain't gonna happen.

[young blood]

getting an allison 6 speed into an obs has about a snowballs chance in hell. go get an LS1 and a nv4500 (5 speed manual)

[Koots]

I was thinking the 6 speeds in the 07-08 trucks 6L90's i think they are called. but i can imagine the price and hassle is not worth it. If you don't like manuals, i would go with a TH400 and a gear vendor overdrive.

[Racking9398]

the allison was a 5 speed

[Koots]

thr allison was a 5-speed it is now a 6 speed.

[dmbaile]

thr allison was a 5-speed it is now a 6 speed.


I thought that was the case. Sounds like it might be more hassle than it's worth. I don't have another car to drive around while the truck's torn up. I need to do some research is what it looks like.

[98GreenMachine]

the allison was a 5 speed

There was/is a 5 speed made, the 2000 series, but it was never in a Silverado. The Allison 1000 series transmissions that are used in the Silverado pickups are 6 speeds.

[Koots]

The allison is a big and heavy transmsission, probably very priey as well, so i would vote a "no" for that idea.