94 k2500 transmission, what's involved with

Edited the question for clarity and the correct name of the model!

It is worth a try. Back of the engine to the transmission should be the same. Others have done engine swaps in the link.

https://www.google.com/search?q=will+a+engine+from+a+94+sonoma+rwd+swap+with+a+94+sonoma+4wd

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All 4L60E /4L60/700R4 have the same gear ratio which can not be modified. ..swap the 94 internal harness into 95 and 96 transmission

This year of GM Transmission doesn't have a vacuum modulator, it is all electronically controlled. And yes a shift solenoid can cause this but that should turn the check engine light on and set a fault code.

welcome to modern cars, the newer cars have a TCM.
you can just swap a mech, trans for a electronically swifted trans.
I swapped, you meant.
its not clear what you are doing here,.
why are you swapping engines
and are you expecting both cars to run? which makes above line odd.
no?

You might want to replace the filter in the transmission and make sure ththe fluid clutch is operating correctly. Both of these checks are relatively cheap compared to rebuilding or replacing your engines transmission. Hope this helps.

Change the filter and flush the transmission. If that doesn't work, it needs to be rebuilt. Seldom is a transmission an easy or cheap fix.

It can be done. It's the same block as a 350 so you should be able to use the same parts as a 350 swap. It's a tight fit for sure and requires some specialized parts. Look around on the internet for 350 swaps or check some of the off road mags. You shouldn't have any trouble finding complete swap kits or step by step instructions as well as what type of special pieces you will need. Hope this helps.

the engine was not a match from the same building codes as yours. computerized engine swaps must be exact swaps or problems will arise such as yours

Yes.

If your idle is going from 500rpms to 1000rpm's fluctuating at and idle your EGR valve is probably carbon up and needs cleaned or replace.