International Full Size Jeep Association

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-   -   4L80E-4L60E swap questions (

Will Morris 07-03-2004 08:05 AM

Here's the deal, I'm thinking of putting an LT1 in my Jeep. It currently has a 2wd 4L60E mated to it. I know that 4L60Es and 4L80Es are both computer controlled, however my question is are they interchangeable? I already have a 4L80E 4x4 trans mated to an NP205. The trans needs rebuilt, but other than that, it's already mated to a transfer case with the correct side drop. I'm thinking this might be a better way than adapting the 2wd 4L60E, but only if I don't have to mess with any computers, reprogramming, etc. Also, GSMikie, is it possible for me to rebuild a 4L80E myself with a good manual? I already have the manual, just wondering if I'm better off paying for a rebuild. So GM techs, what's the best bet?


The Anti-Chrysler 07-03-2004 02:26 PM

Both trannies are interchangable, however the 4L80 is heavier, longer, and has slightly different gear ratios. The 4L80 is not much like older trannies in that the shifting is all electronic servo controlled. I don't know if gsmikie has dove into these yet. Same principle, but a different animal.

You could always just get a 4l60E from a 1/2ton Chevy 4x4, and use the LT1 converter to get the right stall speed. Then you keep the 4l60's lower first gear and smaller case.

If you plan on towing, etc., you might want the 4l80. Although keep in mind the cam in the LT1 is designed for sports cars, not trucks, so it's going to want higher gears than you might otherwise need.

Lastly, I've been told to stay away from Vette LT1's for swaps. Can't remember the reason off the top of my head, but I know the Camaro / Firebird motor is an easier swap, and it's slightly better tuned than the Impala version. I have a '95 Z-28, and it's a real good motor. Make sure you get at least a '95 to get the optispark version that's improved.

Will Morris 07-04-2004 05:10 AM

Thanks for the info on the interchangeability. I've heard of some Impala guys having trouble keeping the tranny alive with more power due to the weight of the car and the power, so running a 4L80E may be a better bet since it will see some hard use. Since I already have a core, I may go ahead and splurge for a rebuild or pay for it to be rebuilt since they do seem to be a pretty complicated animal from what I've seen. Plus it's about on par with the cost of an adapter from Novak for the 4L60E. The extra length and weight isn't really a concern for me since it's going into a big heavy FSJ anyway.
As far as the Corvette swap, someone said the wiring was harder, but on the other hand the Corvette LT1s were suppose to come with 4 bolt mains. I really need to find someone to talk to about wiring everything.


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