96 Tahoe Transfercase

[khenry]

I picked up a 96 Tahoe 4X4 with no motor, trans, wiring and no engine control module. I installed a 383 motor, 4L65E trans, MSD EFI and TCM. The RPO codes for the rear end are, GU6 3.42 ratio and G80 posi. Tire size is, 245/75R 16, the transfer case is a 243C electric with a 2.72 ratio. My problem is that its running RPM was 4,000, going 40 mph, in 4th gear. Found out I was in 4wd low and front differential was not engaged due to missing wiring. I hooked up a switch to the shift actuator and got it out of 4wd low.
And know I am at 3,000 - 3,500 rpm, 45 mph in 4th gear. I am thinking I might be in 4wd high? If so how can I get it into 2wd high? Most wiring to transfer case, 4low, 4hi, 2hi switches, and trans was removed when I bought this truck. For testing I removed driveshaft to front differential.

Thank you.

 

[bigfootchiro]

4Hi will not change RPMs compared to 2WD, if I’m not mistaken. You posted about this before, right? 3000 rpm at 45 still seems very high, especially with 3.42 gears. I know I asked this last time, but are you are POSITIVE you’re in 4th gear? That sounds more like 3rd. Even an unlocked 4th wouldn’t be 3000 RPM

 

[khenry]

Yes positive in 4th. Yes I posted before and got it out of 4wd low and it made a big difference. But yes its in 4th, I feel it shift plus the trans controller LCD screen shows it in 4th. Was wondering if it could be in the transmission gearing? It had a 4L60E and I put in a 4L65E?
Thank you for your reply.

 

[bigfootchiro]

I think the gearing is the same for both trannys. If different, it’s probably negligible and won’t make that big of a difference in RPM. Do you have a scan tool or OBD reader that will read your RPMs?

 

[khenry]

Yes, the MSD transmission controller has a hand held to view data, and also the MSD fuel injection system has a hand held, and they both read the same RPM and the tach.
Thanks for your help.