Strange T-350 issue

GLHS60

GLHS60

Well-Known Member
Stock column shift, non-lockup T-350 suddenly developed an issue trying to shift into high gear.

It's been fine the past couple of years but now it feels like its binding severely on the 2-3 shift.

It's normal otherwise, strong reverse, no noise, clean fluid, 1-2 shift is fine.

It feels like 2nd won't release to let 3rd engage, just binds up so I drove home in 2nd. .

Governor, modulator, kick down cable couldn't cause this, any one have any ideas??

Thanks
Randy
 
It could be the Vacuum modulator, Kickdown cable issue, and the Governor is stuck as you stated.
Its been a long time since I worked on a TH 350 Trans.
The last I solved by swapping in a Known good used Governor.

One Snake Oil that works Nice in Transmissions is SEA FOAM.
Add the Full can in.
Does a good job freeing up stuck shift valves.
 
I'll bet you need to adjust the Throttle valve cable. On most most TH350s there is a stamped steel button on the cable where it clips into the bracket on the intake, hold this button in with your thumb and pull the cable back toward the firewall, this is the tightest setting. Now get in the car and hit the gas pedal to the floor. You should hear a ratcheting sound, now the cable is adjusted. Are you running a high lift/ long duration cam? If so you may need a "lighter" modulator. If it's the modulator with the Allen wrench adjuster screw you can try a dusting down.
 
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Or have a sticking governor. There's a cover on the side of the trans you can take off & remove the governor. As you lift the weights on the governor the spool valve should move freely through its entire range of travel and return when you let go. If it's sticks try cleaning it with brake cleaner.
 
Appreciate the replies but the " Governor, modulator, kick down cable couldn't cause this"

It wouldn't shift to 2nd properly if any of these were at fault.

1-2 shift is fine, when it tries to make the 2-3 shift, 3 is applying, but 2 wont release, this is when the "binding" occurs.

Its trying to be in 2 and 3 at the same time, leave it in 2 and its able to shift 1-2 and can drive.

Strange issue for sure.

Thanks
Randy
 
Auto shifts are controled by governor pressure, the governor is a centrifugal device that opens a spool valve, based on speed. The modulator and throttle valve are used to supplement the governor by sensing engine load and throttle angle. This is what makes the trans shift later, or down shift when you floor it. If you are getting normal 1-2 shifts, but no 2-3 shift, you may have a sticking governor, or a misadjusted manual valve/shifter cable. I covered above on my post 3 how to free up the governor. I always try the cheap easy things before looking for the more difficult problems.
 
It's a stock 400 SBC with a T-350, 1981 Pontiac Parisienne 2 dr.

Keep in mind the 1-2 shift is perfect so that rules out governor, kick down cable, modulator.

All can cause delayed or no shift, my issue is 2nd won't release when 3rd engages.

It would burn up in about 10 seconds if I left it binding (overlapping) trying to complete the 2-3 shift.

Luckily, when it happened in slow moving heavy traffic, I pulled the stock column shifter down into 2nd and kept going.

Happens if I start out in D, 1-2 good, 2-3 binding.

Same thing if I start out in 1, manually shift to 2, good, manually shift to D, no good, binding, 2nd won't release.

Certainly not a common T 350 issue!!

Appreciate the input !!

Thanks
Randy
 
Another possibility is a Hydraulic Cross Leak.
The Valve Body Gaskets Failed.
Or a Steel Checkball is is stuck in the Steel Valvebody seperator plate.
Not a commen issue unless the the car is Drag Raced Hard.

On A Fords C6 You leave the Valvebody gaskets out for severe Drag Race Use.
No gaskets to blow out and fail.
Did that when I when I rebuilt the C6 Trans in my 1973 Lincoln Mark IV 460 Big Block Continental .
Worked fine on the street.

Never tried leaving out valvebody gaskets on GM Transmissions .
Nor do I Recommend.
 
I had a pretty good trans guy explain what he thinks is my issue.

The intermediate sprag, or one way clutch, is jammed up 2nd so can't freewheel

2nd has to freewheel when direct drive, or 3rd engages..

Normally the int sprag breaks and the trans has no 2nd.

Mine probably cracked and jammed at the same time.

Thanks
Randy
 
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