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Well I sent my truck to the shop on Thursday morning and I found out from their diagnosis that I am missing a VSS sensor and that my transfer case is "incompatible" with the engine/tranny setup. Whatever. SO should I adapt a VSS sensor into my original transfer case or should I have that sensor deleted out altogether and make the PCM think its a 2wd? Or would that be bad?
you should have two speed sensors. Supposedly the front one can be disabled. The two are used to determine slippage. I've wondered if the PCM could be tricked by hooking both sets of wires to one functioning sensor.
I do now, both in the transmission, but I think the computer still thinks there should be a VSS back there in the transfer case. Well I did have one thought though, when I brought it home, the transfer case was locked in 4 wheel drive and I never changed it. Could that be the problem? Maybe it thinks its still in 4 wheel drive?
do you maybe have it tricked into thinking its in tow-haul mode?
Also, have you done a circuit check on the TCC solenoid to see if the windings are good?
Oh ya know, I didn't even think about the towing mode. How do I check that? And if it is in towing mode, how do I change it? No I haven't checked the TCC solenoid but I will definitely look into it.
I'm not sure on the tow mode since I've always run car PCMs. PM GasGuzzler and maybe he can tell you which wire on the PCM triggers tow mode in the PCM.
Tow/Haul switch is wires directly to the 2000 BCM. The BCM sends a Class2 message to the PCM to engage T/H mode. I don't think you have that issue but I'm not sure how some of these swaps work without the use of a BCM.
I also originally missed the fact you have no VSS in the transfer case. Yes, you need it...badly. It makes no real difference if the T/C is in 4WD or not AS LONG AS IT'S NOT IN 4LO. I doubt a 4L80 will shift into OD in 4LO. Also, I'm surprised it shifts at all with no VSS. It's my understanding that the two speed sensors on an 80 are for internal trans slip diagnosis and TCC application. The VSS does all the work for shift timing/pattern, etc.
Here's the GM internal component checks for no 4th gear.
Seals (527) (531) Nicked or cut
Cup Plug (530) Missing
Bolt (26) Loose, broken, or missing
Piston (528) Jammed
Spring Assembly (532) Jammed
Retainer Ring (523) Not seated
Friction Plates (525) Worn or burned
Reaction Plates (526) Worn splices
Housing (529) Damaged or cracked
Housing (504) Broken
Reaction Plates (508) Worn splines
Sun Gear (650) Worn
1-2 Solenoid (313)
• Stuck Off
• Pinched wire
• O-ring failure
• No voltage to the solenoid
No signal to the solenoid
3-4 Shift Valve (308) Stuck
PCM Quad Driver Module Failed
Check the PCM for current DTCs.
Since he has both speed sensors in the trans, shouldnt he be able to run a 2wd PCM and it should shift the transmission perfect regardless of transfer case gearing? Isn't the reluctor wheel on a transfer case shaft 40 pulse, too? Putting the sensor in the transmission should have alleviated the transfer case issue, unless there isnt the reluctor plate in the 80e transmissions that are built for 4wd trucks, correct?