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94 suburban k2500 transmission

R

Randerson2

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Oracle, Az
I just picked up this thing for next to nothing trying to find out what the original tranny was. Previous owner had transmission replaced and it went shortly after. I think he may have had wrong one put in. I see that it may have the 4L60e or the 4L80e. I am trying to figure out what I can put back in. What other models and years will work and if I have to reprogram computer. Any help would be much appreciated.
 
Look in the glove box for the RPO code sticker. ( If it's still there ) MT1 for 4L80 or M30 for 4L60. I'm pretty sure that's what the RPO codes for the transmissions are.
 
Welcome to the forum.

What exactly is happening? Maybe something fixable rather than complete swap.

No way I would run a 4l60 when I can choose the 4l80/4l85, Even if it did come stock. Something went WAY wrong if you dont get 100,000 miles on 4l80- even with a hp built engine. Normal lifespan when engine is mostly stock is 250,000-300,000 miles.
4l60 not good for diesel,big block, big power, towing, etc.
Kinda only good for grocery getter, mostly in cars, and not over 200,000.

RPO codes tell what original trans was iirc. But if gone,
4l60 has pan like more like a rectangle, and 4l80 is kinda oval shapped.
Post a pic of yours, or if needed I will of my 4l80 so you can compare.

There is a good trans shop in Az. A member here mentioned more than once. @WarWagon
 
The 4l60 has 16 bolts and the 4l80 has 17 bolts in the pan if I remember right.

Welcome to the forum. There is some seriously good knowledge on this forum.
 
Right on thanks for all the info I do appreciate it. The pan is square of the one that's in there but that is the second one. With 4l80 what kind of modification is required if any. I got the thing for next to nothing with a blown tranny everything else works well. The guy who did work for previous owner has since moved on so there is no real good info. My guess he saw them coming. As far as what is wrong thing only has reverse and it slips. Strange though fluid doesn't smell burnt. Makes me wonder if there is a chip problem. Are these trannies vehicle specific or are they interchangeable. That's why I prefer my old blazer everything swaps.
 
Look through the threads in the "all other" tranny section that talk about the 4l60e and 4l80e and I think you will find several threads that give good detail about which year works with which. @THEFERMANATOR knows these things, so pay particular attention to what he says. With the square pan you would have the 4l60e.
 
What engine do you have? If it's a turbo diesel or 454, then it would have a 4l80e. If it has a 350 then it was 4l60e. Going to need alot more details on the truck to tell you much. I will say if it was a 4l80e, 94 is a 1 year only, but 95-96 can be made to work semi easily. If it has the 4l60e, then only 93 & 94 interchange directly. It's not a simple swap to go between the 2 transmissions. The 4l60e is around 2 inches shorter, has a 27 spline output shaft vs the 4l80e's 32 spline, the wiring is different in a few ways, programming is completely different, different driveshafts, the crossmember is the same but bolted into different holes, the flexplate on the engine is different, trans cooler lines, different trans support arms, and I'm sure some more I'm forgetting. So yes it can be swapped, doesn't cost too terribly much if you know what parts to scavenge, but it is not cheap if you don't know what you're doing.

That said, a properly built 4l60e can take a good bit of abuse, but this is all guessing without knowing exactly what you have.
 
Welcome to the forum Randerson.
Please, put in Your signature lines the make, year, model and any other pertinent information that would be helpful in diagnosing problems.
That will help those in the know imensely when trying to help You.
If this is a 6.5 Suburban, you are going to love this rig.
 
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