Problem with TH-350 Automatic

80Camaroman

Veteran Member
Nov 16, 2001
2,676
Beavercreek, Ohio, USA
My '80 Berlinetta Camaro has been experiencing some transmission problems lately. It has a modified 355 engine with a TH-350 Automatic transmission. Every once in awhile it slips out of Drive then re-engages when the shifter is in the Drive position. This occurs no matter if my car is in motion or stopped at a traffic light. I did check to make sure the shifter was engaged properly into the drive position and it still happens. It seems most noticable when my car accelerates or attempts to accelerate initially then it pops into gear. I drove the car today and it did this again. I am almost afraid to drive it because I don't want to tear up my tranny and get stuck somewhere. I checked the transmission fluid level and the fluid itself today and all appears normal. To check and see if the shifter cable was out of adjustment, I attempted to start the engine in all gears except Park and Neutral and the engine would not start in the other shifter settings. Anyone have any ideas what would cause this? The old Haynes manual says to take the car to a qualified mechanic if all the above checks out okay. I don't know much about these TH-350 automatic transmissions. Any help would be greatly appreciated. Thanks in advance. ;)

Jim
'80 Berlinetta
 

CorkyE

Veteran Member
Lifetime Gold Member
Nov 4, 2004
11,639
Ringgold, GA
I think the Haynes manual has it right; take it to a tranny shop. Could be a pump going out but who knows until you get into it.
 

gregh

Moderator
Staff member
Lifetime Gold Member
Jun 24, 2003
4,173
Calgary, Alberta, Canada
80Camaroman said:
To check and see if the shifter cable was out of adjustment, I attempted to start the engine in all gears except Park and Neutral and the engine would not start in the other shifter settings.

All this tells you is that the neutral safety switch is working properly, if the shifter cable is stretched or out of alignment, it most likely won't affect the NS switch(it's on the steering column).

I'm not sure if the factory shifter cable has any adjustment in it but that would be the first place I'd look, a new cable would be my 2nd choice & an aftermarket shifter 3rd.
 

80Camaroman

Veteran Member
Nov 16, 2001
2,676
Beavercreek, Ohio, USA
I found a TH-350 handbook at Barnes and Noble. It has a troubleshooting section in it. It says if the TH-350 tranny slips in 1-2 shift, probable causes are:

Low Fluid Level
Low Oil Pressure
Faulty 1-2 accumulator
Faulty 2-3 accumulator-350, 350C and 350B only
Front pump malfunction
Intermediate-clutch malfunction-350, 350C and 350B only

Looks like I will have to take my car to a tranny shop to have these checked out. I don't have the right equipment to test these myself. Thanks for the help guys.

Jim
'80 Berlinetta
 

gregh

Moderator
Staff member
Lifetime Gold Member
Jun 24, 2003
4,173
Calgary, Alberta, Canada
Is the tranny slipping or popping out of gear? Very different diagnosis there.
If it's slipping: is there a burnt smell to the fluid? Is it a bright red or dark red?
 

80Camaroman

Veteran Member
Nov 16, 2001
2,676
Beavercreek, Ohio, USA
gregh said:
Is the tranny slipping or popping out of gear? Very different diagnosis there.
If it's slipping: is there a burnt smell to the fluid? Is it a bright red or dark red?

The transmission acts like its slipping out of gear rather than poping out of gear. The color of the fluid is a bright red. I didn't notice any burnt smells coming from anywhere. I forgot to mention that the speedometer needle was bouncing up and down by 5 mph when I was driving the car at 35 to 40 mph, which it rarely ever done before. Don't know if that might indicate something.

Jim
'80 Berlinetta
 

SBnBOTL

Veteran Member
May 13, 2008
270
USA
Also just maybe you could check under the hood on the steering colum there is a lever/cable there that can loosen up. at least it did on me, but i found that from other problems. maybe this helps
 

PBA

New Member
Mar 31, 2008
5
Calimesa, California
The manual valve inside of the transmission sounds like it is out of adjustment. Look at the ATSG manual or any TH350 TransGo Shift kit instructions. They will show you how to make the necessary change here to solve this. Dana
 




Top