shifter jumps out of gear

[CHEVY LOUston]

I have a 1991 k1500 with the 700r4. Whenever i take off hard, my shifter, jumps out of OD into neutral. I have had the trans rebuilt at a very reputable shop. That did not change the shifter problem. I also replaced the column shift spring. Also replaced engine and trans mounts. I cannot find anything anywhere with any info with this issue. Has anyone experienced this before and how did you rectify it?

 

[Erik the Awful]

I also replaced the column shift spring.

?

The detent is in the transmission. Does your shifter still have the notches for each gear?

 

[NickTransmissions]

I have a 1991 k1500 with the 700r4. Whenever i take off hard, my shifter, jumps out of OD into neutral. I have had the trans rebuilt at a very reputable shop. That did not change the shifter problem. I also replaced the column shift spring. Also replaced engine and trans mounts. I cannot find anything anywhere with any info with this issue. Has anyone experienced this before and how did you rectify it?

To be clear, you are seeing the shifter on the steering column physically move to 'Neutral' while in 'Drive' as you're taking off under heavy acceleration in first gear?

Was this issue was present before you had the transmission rebuilt and before you replaced parts on the column as well as engine/transmission mounts as well as now?

Did you ask your transmission builder about it or inform him this was happening when you took the trans (or truck) in for the transmission overhaul? If so, what did he say about it?

The rooster comb and detent roller control the position of the manual valve in the valve body which is moved incrementally by one detent position each time you move the column shifter from one position to the next...The rooster comb is part of the transmission's internal shift linkage, which includes the manual valve actuator arm that hooks into the manual valve itself in the valve body; the rooster comb slides onto the selector shaft via two flats machined into both. The rooster comb is secured to the selector shaft by a 15mm nut that has to be tightened to about 15-20 ft lbs otherwise it could come loose. Otherwise the rest of the external linkage is mated to the selector shaft via a 15mm nut on the outside of the transmission and takes about 20-25 ft lbs.

Is that nut tight and exterior linkage correctly set up and in good shape?

 

[movietvet]

To be clear, you are seeing the shifter on the steering column physically move to 'Neutral' while in 'Drive' as you're taking off under heavy acceleration in first gear?

Was this issue was present before you had the transmission rebuilt and before you replaced parts on the column as well as engine/transmission mounts as well as now?

Did you ask your transmission builder about it or inform him this was happening when you took the trans (or truck) in for the transmission overhaul? If so, what did he say about it?

The rooster comb and detent roller control the position of the manual valve in the valve body which is moved incrementally by one detent position each time you move the column shifter from one position to the next...The rooster comb is part of the transmission's internal shift linkage, which includes the manual valve actuator arm that hooks into the manual valve itself in the valve body; the rooster comb slides onto the selector shaft via two flats machined into both. The rooster comb is secured to the selector shaft by a 15mm nut that has to be tightened to about 15-20 ft lbs otherwise it could come loose. Otherwise the rest of the external linkage is mated to the selector shaft via a 15mm nut on the outside of the transmission and takes about 20-25 ft lbs.

Is that nut tight and exterior linkage correctly set up and in good shape?

Good to see you over here at this forum. I just joined because of my girls 1990 K2500. I may be contacting you soon because of a vibration in the truck at about 45 mph to 50 mph and I have inspected everything I can think of.

I was going to reach out to you at the T/Y Forum to check this thread out. Have a Merry Christmas and a Happy New Year.

 

[Schurkey]

I have a 1991 k1500 with the 700r4. Whenever i take off hard, my shifter, jumps out of OD into neutral. I have had the trans rebuilt at a very reputable shop. That did not change the shifter problem. I also replaced the column shift spring. Also replaced engine and trans mounts.

IF the trans is assembled properly, and
IF the engine 'n' transmission mounts are in good condition, and
IF the steering column and linkage down to the trans are in good condition,

About the only thing that left is body/frame flex when stressed by acceleration.

I'd be looking at the cab mount cushions/hardware, and inspecting for structural failure (rust, cracking, collision damage) to the cab especially around the dash area where the column bolts to the structure, and the frame rail brackets that secure the linkage pivots.

There'd be a wildly-unlikely possibility that the rear leaf springs or spring hangers are so wiped-out that the axle pushes forward on hard acceleration, jamming the driveshaft into the back of the transmission, which might shift the whole engine/trans in a way that affected the shift linkage...but that'd be REALLY hard on...everything...including the engine/trans mounts.

Before I replaced the body mounts and hardware on my 'Camino, the thing was a flexy, rattle-trap that the doors wouldn't open or close properly. Stuffing fresh (Polyurethane) body mount cushions and new bolts into place made the whole car enormously more rigid. I could tell that the car was stiffer before I even got it off the jack-stands afterwards.

 

[someotherguy]

Related but unrelated, who remembers when GM engine mounts were re-designed as a "cage" style to prevent total separation when the rubber bond failed? I know it was likely at some point after 1982, because I helped someone with an '82 Cutlass Supreme that thought he needed a new transmission because when you stepped on the gas, it would pop into neutral. Engine mount was bad and let the engine lean way over, forcing the mechanical linkage into neutral.

That was somewhat more preferable of a result than my '63 Suburban that floored the gas pedal when the engine leaned over due to failed mounts. Quick thinking had me manually shifting the TH400 (swapped) into neutral so the engine would settle back into place and let off the pedal. Come to think of it, that truck taught me a lot of "act fast" lessons, like when a brake flex hose failed at speed and I lost all brakes thanks to the single bore master cylinder setup.

Richard

 

[movietvet]

Related but unrelated, who remembers when GM engine mounts were re-designed as a "cage" style to prevent total separation when the rubber bond failed? I know it was likely at some point after 1982, because I helped someone with an '82 Cutlass Supreme that thought he needed a new transmission because when you stepped on the gas, it would pop into neutral. Engine mount was bad and let the engine lean way over, forcing the mechanical linkage into neutral.

That was somewhat more preferable of a result than my '63 Suburban that floored the gas pedal when the engine leaned over due to failed mounts. Quick thinking had me manually shifting the TH400 (swapped) into neutral so the engine would settle back into place and let off the pedal. Come to think of it, that truck taught me a lot of "act fast" lessons, like when a brake flex hose failed at speed and I lost all brakes thanks to the single bore master cylinder setup.

Richard

Been there and done that with my 65 C10 when a brake line failed as I exited the highway on the ramp. Some tricky steering and down shifting and horn honking. This was when I lived in a salt on the roads state of Mo. Freakin' rust, I hate it. So glad I live in the rust free PNW now.

 

[someotherguy]

Been there and done that with my 65 C10 when a brake line failed as I exited the highway on the ramp. Some tricky steering and down shifting and horn honking. This was when I lived in a salt on the roads state of Mo. Freakin' rust, I hate it. So glad I live in the rust free PNW now.

My '63 Suburban was such a rust bucket you could watch the front tires rolling through the forward floorboard area, and occasionally a rock would fly up and hit the ceiling. I later patched 'em up with roofing tin, pop rivets, and spray undercoating. It was still a cool truck, though! It was 350/TH400 swapped and was the Energizer Bunny of trucks. All the wear and deferred maintenance in the world wouldn't stop that truck. I was young and broke - was my first truck, fourth vehicle owned.

Richard

 

[GrimsterGMC]

Related but unrelated, who remembers when GM engine mounts were re-designed as a "cage" style to prevent total separation when the rubber bond failed? I know it was likely at some point after 1982, because I helped someone with an '82 Cutlass Supreme that thought he needed a new transmission because when you stepped on the gas, it would pop into neutral. Engine mount was bad and let the engine lean way over, forcing the mechanical linkage into neutral.

That was somewhat more preferable of a result than my '63 Suburban that floored the gas pedal when the engine leaned over due to failed mounts. Quick thinking had me manually shifting the TH400 (swapped) into neutral so the engine would settle back into place and let off the pedal. Come to think of it, that truck taught me a lot of "act fast" lessons, like when a brake flex hose failed at speed and I lost all brakes thanks to the single bore master cylinder setup.

Richard

I had similar experience when I swapped a 350/TH400 into my English Bedford J1 truck (Pickups were still a dream back then) and one of the engine mounts I used broke. I didn't realize until I pulled out of a side road into traffic and when I gave it some gas to get moving the engine leaned on over against the steering rag joint (remember this was a right hand drive) and when I went to turn the steering wouldn't move and I went straight ahead. Luckily I realized something was up real quick and backed off the gas and truck turned as it should have. Pulled over and checked it out but with the engine sitting back down again everything looked good. So i headed off again, although very cautiously, and it done the same thing at the next intersection that's when the light bulb in my brain went off and it all started making sense. I was able to turn it around and go back home with minimal gas got it fixed up.

 

[PlayingWithTBI]

who remembers when GM engine mounts were re-designed as a "cage" style to prevent total separation when the rubber bond failed?

yeah, I had the motor mounts tear apart too on my '63 Chevy. I couldn't afford new ones so, I stripped all the rubber off and welded them together - never had a problem after that