aahrested

C5 RPM transmission just installed. along with a diff change 2:73 to 3:42, both from RPM. A short test drive to determine if I can drive it to a Corvette shop for a tune revealed it would not shift out of first gear

C5 Pete

Well, without a tune, the trans won’t know it’s supposed to shift.

dankhts

when I changed all mine it shifted but was all goofy until I set up the shift points/speeds/TC lock up points etc but it still shifted, perhaps something is askew!

RedRiderZR1

With the rear gear change, it should still shift. It would probably shift short compared to what it used to, but it would shift. When you changed gears, are you sure you connected the VSS (Vehicle Speed Sensor)? Do you get a speedometer reading on your cluster? If you manually shift the transmission from first to second, does it shift then?

Check codes and maybe a wiring issue, blown fuse, loose connection.

Here is how to check for trouble codes
http://www.c5forum.com/ayc/dtcdic.php

Fast one

There's an electrical connector for a speed sensor at the top of the transmission or differential that needs to be plugged in, if it isn't the car won't shift out of first.

aahrested

Thanks, I will put it back up on my lift today to check but, I am quite sure I did not miss any of the connections. Actually, I did get it to shift momentarily from 1st to second up around 5000 rpm. I have a long, steep, driveway, and as I drove up the drive it acted like it was slipping. It was really revving high rpm to make it up. The instructions stated it should take 10 to 12 quarts of Dextron III. despite several attempts, I was only able pump about 7 quarts in. So, perhaps after driving it a few hundred yards it will take more. I'm not sure but, I will check that as well. I finished the install several days ago but, the roads have been a mess so, I was not able to test drive it until Saturday, when, of coarse RPM is closed. So far they have been great to work with, and I am hoping this whole thing is something simple. I put this question out because I had trouble waiting till Monday, after all the work I put in, and was hoping someone could put my mind at ease.

493lszosix

Was the torque converter replaced? If it’s new did you make sure to fill it with trans fluid too?

Brad Kirby

Uh, how did you fill the transmission? It should be done with the car level, fill plug out, and engine running. Fill until it comes out, put plug in, go have fun.

tblu92

Ok When making a rear gear change on a C5/C6 you DO NOT have to make a speedo correction HOWEVER you do need to make a shift point correction for both the P/T up and down shiftpoints and more importantly the WOT both UPSHIFT and DOWNSHIFT mph speed shift points!!

Going from a 2.73 rear gear to a 3.42 rear gear requires a -25% change on your WOT shift speeds both for WOT upshifts and WOT downshifts
IF you do not make these WOT corrections the trans will skip over the WOT RPM shift points and hit the "safety rev limiter" and NOT shift
It is rather more complicated than this however the basic starting point would be to SUBTRACT 25% to both the WOT upshift speeds and the WOT downshift speeds As an example if your 1-2 WOT upshift speed is 45 MPH then subtract 25% to that do that for the DOWNSHIFT speeds at 2-1 at WOT as well Do this for the 2-3 and 3-4 and the 3-2 and 4-3 WOT speeds as well--

Bruceb66

Hey tblu92 - Sounds like you have some expertise with this topic. I've also been planning to swap out my 2.73 diff with a 3.42 diff next month, actually bought the 3.42 diff last month. However, the more I've been reading about the intricacies of shift point reprogramming, I'm starting to get cold feet....For an experienced performance shop, aside from swapping out the differential itself which should be fairly straight forward, is the programming aspect more of an art than a science? Or should it be pretty basic stuff for an experienced tech? Thanks.

lionelhutz

On a new or rebuilt transmission you need to run it through every gear while filling it. I highly recommend you run run it and shift it while it's on the lift or the jack stands so you can hit every gear. Otherwise, If you just fill it in neutral it will end up low on fluid when it does shift into the different gears.

The last 4L60e rebuild I filled when in neutral got low enough in fluid that it lost line pressure once it shifted to second while on the jack stands.

tblu92

It is actually basic EFILIVE software allows you to do both P/T and WOT shift corrections with a "one click " entry
This will get you very close---all the P/T shifts will be spot on but sometimes the WOT up/down points may require another adjustment
The more modded your eng is the more chances it may skip over the shift point RPM and hit the safety rev limiter---
The thing they call the "split" the difference in RPM between the shift at WOT RPM and the actual MPH RPM on a stock engine is around 600 RPM---When adding HP and TQ ( lower rear gears multiplies TQ) and acts just like engine mods_ you may have to increase the "split " as high as 1000 to 1200 RPMs------
This is the technical explanation Simply said just LOWER both the up and down shift MPH's at WOT--1st by the 25% then again 5 % at a time until it shifts at WOT correctly