Transmission wont go into reverse on my 95 GMC Jimmy SLT 2wd

[Thomas1973]

Hi,

Greetings from Sweden, Europe!

I have a 1995 GMC Jimmy SLT (2wd) with automatic transmission. The car is reliant and in good shape, it runs smooth to and from work every day.

When I got it back in October last year it could move in reverse gear, however it made some noise and shaking when driving in reverse.

Last month I had the fuel tank, fuel and brake lines (tubes) replaced, I even asked the garage to check the transmission fluid. When I picked up the vehicle at the garage it could not move in reverse gear at all.

The car runs perfect in all forward going gears but when I put it into reverse it is exactly like having it in Neutral. The engine sounds normal and using the speeder just brings up the RPM but doesn't move the car at all.

The garages that I have spoken to (including one specialized in US cars) claims that only solution is to replace the entire transmission...which would cost more than the car is worth - I would like to keep my little old truck and I suspect that there might be a more simple root cause to the problem.

The following indicators make me suspect that the problem is not in the transmission itself:

- When putting the car into Reverse gear, the reverse light on the back of the car does not lit up (Yes; I did chceck that the lamps are okay).

- Smooth running in all forward gears, no noises.

- No probelm in placing gear shifter into reverse mode, indicator lights up.


Anyone who has experienced something similar or can point at a cheaper solution than changing the entire transmission, then please do not hesitate to answer to this thread - Thank you.

Best regards
Thomas

 

[Molson02536]

Hi,

Greetings from Sweden, Europe!

I have a 1995 GMC Jimmy SLT (2wd) with automatic transmission. The car is reliant and in good shape, it runs smooth to and from work every day.

When I got it back in October last year it could move in reverse gear, however it made some noise and shaking when driving in reverse.

Last month I had the fuel tank, fuel and brake lines (tubes) replaced, I even asked the garage to check the transmission fluid. When I picked up the vehicle at the garage it could not move in reverse gear at all.

The car runs perfect in all forward going gears but when I put it into reverse it is exactly like having it in Neutral. The engine sounds normal and using the speeder just brings up the RPM but doesn't move the car at all.

The garages that I have spoken to (including one specialized in US cars) claims that only solution is to replace the entire transmission...which would cost more than the car is worth - I would like to keep my little old truck and I suspect that there might be a more simple root cause to the problem.

The following indicators make me suspect that the problem is not in the transmission itself:

- When putting the car into Reverse gear, the reverse light on the back of the car does not lit up (Yes; I did chceck that the lamps are okay).

- Smooth running in all forward gears, no noises.

- No probelm in placing gear shifter into reverse mode, indicator lights up.


Anyone who has experienced something similar or can point at a cheaper solution than changing the entire transmission, then please do not hesitate to answer to this thread - Thank you.

Best regards
Thomas

Put a line pressure gauge (visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" boost valve (easy fix in pan).

Common failures on 4L60E, symptom: Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell. It is possible to remedy a fluid problem by removing the checkball from its cage in the case in the rear of the trans may help (must remove valvebody), or adding a high-viscosity additive such as Lucas Transmission additive or other seal restorer product. May also have worn boost valve (can replace in the pan).

I don't think you have a broken sunshell, start with checking your transmission line pressure and replace the Boost valve, stock i believe was 0.470". Go with the 0.490" boost valve and do not flush out your transmission, that is going to make your transmission to fail.

Chances are the internal seals are hard with age and heat , frictions worn down thin. Two items create reverse gear. Reverse input clutches and the low/ reverse clutch pack. One or both have failed IF there is no reverse. Neither of these clutch packs affect / function in forward gears. The manual valve directs oil to the reverse passages , not the shift solenoids. You can unplug the 4L60e main trans case connector and the trans will shift to reverse (If reverse functions).

1 - 3 shift with the trans may be skipping 2nd gear. Often folks mistake a 1-3 shift for a 'late' 2nd gear shift. Backing offf the throttle may be allowing a weak 3-4 clutch pack to apply. IF that is happening, the sun shell has broken or stripped out.
When the sun shell breaks , there is NO reverse , 2nd gear or 4th gear. You did not indicate if Over drive (4th gear) functions.... just that the 'shifts" above that seem fine. Do you feel - see -think the trans has 3 complete shifts? 1-2 shift (late) , 2-3 shift .. then the shift to 4th gear? 2nd gear and 4th gear are the same band. Usually if one gear does not work the other gear does not work either.

Keep me posted, be glad to help you.