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Tranny computer for 6.5 to 6.2 swap w/4L80

Gatewaybroker

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Bought a ‘99 3500 4x4 that had a 6.2 installed in place of the bad 6.5L. The exhaust and breather had to be altered, but it seems ok. The 4L80 will not shift correctly but I’ve heard you can use a TCM from a different application or get a stand alone TCM. I’m not worried about anything other than drivability. Not trying to break the bank on a old work truck.
 

smokymtn65

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I would think if the electronics are in place and and it has the DS4 could be wiring issue tranny should work as before if it good. 1623080868588.pngBD2

1623080916756.pngDS4
 

WarWagon

Well it hits on 7 of 8...
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We need pictures. Engine, close up of IP, and transmission. Don't assume they swapped the 1999 trans to a 1983. I suggest it's a simple long block engine swap as a 6.5 is more or less just a punched out 6.2. If there is a large wire harness plugged into the transmission: it's likely a 1999 electronic.

Troubleshoot it like it's the 1999 transmission and the engine replacement is just that. Pull codes, check the trans oil level and condition...

Now if they also swapped another year 4L80E in that could be a problem depending on what year they grabbed.

Won't shift correctly is vague. It specifically does or does not do what and when?
 

MrMarty51

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A series of numbers should be listed on tags to the side of the transmission. See if the numbers on those tags is legible. If so, post them in here. Someone might be able to decipher what trans it is.
 
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