92 Auto Trans not quite right

[red88gt]

I recently installed a new / used 3800 engine and 4T60E trans into my tired 92 Transport. The engine trans combo is out of a 92 Bonneville with slightly over 110,000 on it. I searched for quite a while to find the correct year & model so that I would'nt have problems with the install. This was an exact replacement for the previous engine & trans. It runs pretty good now except that the trans doesn't seem to shift exactly right. It goes through all the gears as it should and the TCC locks up fine. It just seems to rev out further than it should before shifting. On the freeway, it downshifts and the TCC disengages fairly quickly when you apply more throttle. Needless to say, in this condition the gas mileage is suffering. It runs fine otherwise and is pretty peppy. Are there any adjustments to be made to this setup ? I can't find a ATV cable on this unit. Thanks for any advise.

[guido0136]

I'm no expert, but the computer might be the issue. I'm sure LMP can confirm or deny this.

BTW what was the total cost of this as I would like to do the same to my '93 some time soon.

[maxwedge]

All electronic no adjustments here, check the tps on a scanner this could cause delayed shifts, also could be internal with some of the solenoid issues on these units, or the relearn is in process,

[LMP]

My first interrogation would be about the gear ratio. The gear ratios are not the same in all these 3800-4T60 combos..and having driven both transport and bonnie in the same year models, I remember the bonnie revved slightly faster.
I have the transmisison codes for '93...
Of course, the computer firmware matches the intended transmisison ratio to appreciate speed as well as TCC slip....and some issues have been reported with mismatches. SO...I'd pay some attention to that detail before anything else.

[maxwedge]

Good info LMP, I could see a higher rpm for a given speed or lower for that matter depending on the gear ratio, It would seem with a lower numerical final drive the additional load on the engine at a given speed would cause more frequent down shifts, but excellent point made here.