97 Tahoe limp mode?

[WesAbbott]

Hello! I recently purchased a 1997 Tahoe 4wd 5.7.. i was unaware of what limp mode was.. the p0785 code is the only code being thrown let me tell you a little bit about the problems I'm having any help would be appreciated.

-truck revs high and shifts hard from the first 2 gears(I am not sure its 1-2 because i cannot put the truck in 1st maually it stops at 2 on the dash) then it stays in the next gear

-speedometer bounces or doesnt work at all, all the other gauges work including tachometer (gas gauge bounces but that may be a different issue.

- the previous owner removed the front drive shaft for 4wd (stated he wanted better gas mileage) there are 2 plugs that arent plugged in not sure where they go or if they were for the 4wd

I have installed a new TPS didnt help, could it be the speed sensor? i was going to purchase the ignition switch because it seems to be a common problem, but it seems to me that most people with ignition switch issues lose all gages on cluster.. truck is in great shape other then that and i just want to get it solved.

also if it is third gear im stuck in, and i Believe it is because when i drove it home at about 45-50 i was running at about 3000 rpms and of course it wouldnt go into OD.. is it ok to drive it for my short commute to work as i only go about 45-50 the whole way

 

[bigfootchiro]

https://www.obd-codes.com/p0785

Here’s a good description about that code. Make sure to read the “note” section about the 3-2 shift and the causes.

 

[WesAbbott]

Thanks Ive read that one a few times over.. Im almost certain it is electrical and that the solenoids are good.. so many people talk about how they replace the solenoids and still have the problem

 

[WesAbbott]

im also wondering about the drivability while i assess the situation.. like i said its not a far trip and i dont go above 50 mph

 

[drakon543]

it also sounds like your stuck in 4lo aside from the speedo bouncing and not shifting manually into 1st. my tahoe was shifting very hard and seemed like it wasnt grabbing 4th when i first bought it. my problem was the front actuator kept blowing the 4wd fuse and the neutral safety switch kept it from going back into 2wd.

 

[WesAbbott]

drakon543 is that possible even though the 4wd drive shaft in the front has been removed

 

[bigfootchiro]

Also, not manually going into 1st could be do to the shift linkage in the driver side of the transmission. It is adjustable, so may be out of adjustment.

 

[WesAbbott]

im pretty sure its in limp mode which is why its not going into 1st.. the trouble codes said electrical issue AT the transmission.. any thoughts on repacing speed sensor or ignition switch

 

[drakon543]

4lo is in the transfer case not the front end. so yes it would be possible. only suggesting it as its a cheap easy fix and my tahoe had the same symptoms as yours aside from that trouble code.

 

[WesAbbott]

4lo is in the transfer case not the front end. so yes it would be possible. only suggesting it as its a cheap easy fix and my tahoe had the same symptoms as yours aside from that trouble code.

What did you do to fix the problem and get it out of 4lo