700r4 Popping into Neutral

[Fortrex]

I have a 1980 GMC pickup, 2wd single cab long box. The truck was a factory 350 oldsmobile diesel with a 3 speed auto, and the truck has been through a few different drivetrain combinations since then but it currently has a 305/700r4 combo. I believe the shift linkage is still the original 3 speed linkage as it stops at 2nd gear and won't go down into first, the dash indicator was swapped to a 4 speed indicator though. The transmission works great, the only issue is when you're coming onto it the shifter wants to pop up out of O/D into neutral. If you rest your hand on it you can actually feel it push upwards if you step on the gas. I believe it is adjusted correctly, all the gears (except for 1st) are lined up perfectly and they all work as they're supposed to, the indicator is perfectly centered whether you're in park, neutral, reverse, O/D, D or 2nd. Both motor mounts as well as the tranny mount are brand new. Has anyone ever had any similar problems? I have done lots of searching bu haven't found anything yet. Thanks in advance.

 

[MrMarty51]

That is weird.
Look over those motor and transmission mountings real good. Nothing to say one of them is not bad.

 

[Fortrex]

I thought that too, but side by side with a buddy's squarebody while punching it up to 4500rpms my motor seemed to flex a lot less than his did on his ~2 year old mounts.

 

[yevgenievich]

I would readjust the linkage just to rule it out. But also the shifter it self in the column has stops and they might be gone.(where it requires to pull forward to shift)

 

[Fortrex]

I plan on double checking the linkage as soon as I can get it on the hoist. I thought there was no stop between O/D and neutral?

 

[yevgenievich]

I am thinking of the step the requires handle to be pulled away from the dash to shift

 

[Fortrex]

I double checked the linkage and it's adjusted properly and works freely through all the gears.. The truck has dual exhaust, it runs near the linkage but I don't see any marks to indicate any rubbing between the two.