Wheel Stander

I'm sure this question has come up before, but can anyone tell me what the factory RPM shift points are for the automatic tranny in a 1992 LT-1? I was told that this transmission is not computer-controlled and to modify the shift points I would have to install a shift kit and possibly modify the governor, servo and valve body. Is that correct and, if so, what can I expect to spend for the necessary modifications?

tunedport85inject

Correct,you can "tune" your shifting point by changing governor weights and springs.You can also put new boost valve (larger .500) and intermediate valve and spring from Sonnax into your tranny oil pump (you can do it by simply removing the pan,just a snap ring to remove to unplug the valve housing inside the pump.As for the governor,you can remove your old unit just removing the governor housing cover;your exaust pipe may interfere,but i was able to drop my governor leaving the exaust on.You can play with weights raising your shifting point, it's a trial and error. A shift kit can complete this trans tuning,usually you have to enlarge some oil passages,and you can find some larger valves depend on what type of kit you choose.

see Patc transmission

http://www.transmissioncenter.net/pe...automotive.htm

http://www.sonnax.com/parts/2330


corvette governor $ 44
governor weight kit $ 49
boost valve $ 44

c4cruiser

One thing to consider for raising the shift points is that the ECM has a built-in fuel cutoff that happens at 5850 RPM. So it may not help to raise WOT shift points above that RPM value unless you tune the fuel cutoff out or raise it.

IIRC when I had my '92 convertible, the shift points at WOT were just at or below that 5850 RPM value.

Wheel Stander

You seem knowledgeable when it comes to transmissions. My car is a 1992 LT-1, so would it have the 700R4 or 4L60 model in it? Also, what (if any) difference is there between the two and how might that effect any modifications I might want to make regarding shift points?

tunedport85inject

you'r trans is a 4l60,it was redesigned in 1987 when it was deeply upgraded.most important mod was the adoption of a new auxiliary valve body,but lots of minor mods too.when you comes to raising your shifting point you have to consider what C4cruiser said in post #3.The LT1 is an highier spinning engine compared to an L98 this let you use a lighter tuned governor compared to one mounted on a 4l60 in a L98 engine.When you use a stick trans you upshift when you come in the powerband peek range,there's no sense in spinning an engine over this powerband peek,no more torque or power hp peek over this point and revving over is useless (not to say that a fuel cut off function is built in your ecm).Here you have to fine tune the governor's weight just an hair before max hp power point (ok let say 2 hairs).The boost valve .500 give you max fluid pressure built up and the shift kit makes your gear shifting firmer and crisper.Note here i'm assuming you'r modding the trans for performance ,the result is a firmer ,crisper shifting and a trans that upshift highier when you floor the pedal,revving in the entire usefull powerband.