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1994 4l80e to a 1993 2500 4x4 with same transmission

Otbc_gyro

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So I found a 1994 4l80e transmission for 600.00 that came available because the 6.5l diesel suburban it was in caught fire. The harness and speed sensors were melted but the trans fluid was clean and the owner claimed it had only 18000 km on it. After some time I had a transmission shop install it into my 1993 2500 4×4 with a 454 engine .

The truck is not showing any error codes, but it does not shift unless you let the gas off . I don't believe it goes into 4th at all and the kick down seems almost hyper sensitive.

I should also mention that we used the electrical from the 93 trans that was in there, but did not change the solenoids or torque converter. From reading here I think I understand some of the differences between the years, but was really hoping some one could offer some work around to make this 94 work I the 93 truck.
 

THEFERMANATOR

FRANKENBURBAN
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The short answer is you're missing the 40 tooth reluctor wheel that the output speed sensor reads on your 93. So the ECM doesn't know how fast you're going. You essentially have 2 different transmissions even though both are 4l80e's. There is 91-93, and 94+. They use a different valve body, 91-93 4x4's are the only 4x4 4l80e's to have a reluctor installed, the harness can be different, different style trans fluid temp sensor, and a different pressure control solenoid. You can either open the 94 trans up, add in the 40 tooth reluctor wheel, and swap valve bodies. Or you can get a custom prom burned for your ECM and add in the wiring to tell it when you're in 4low and hook up the speed sensor input to the ECM from the VSSB. The catch is your transfer case is setup so it only can use the 2 pin switch and not the 3 pin that tells 4low and 4x4, so you will have to make your own 4 low switch.
 

Otbc_gyro

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Thanks for your response. I guess I should have just had my 93 transmission rebuilt. I assume that by opening up you mean it has to be pulled out and basically rebuilt . Not something that can be done from taking the pan off.
 
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