TH 350 shift issues

[Mlcdc1]

shifting issue with TH350-Shifts great until it gets warmed up and then intermittently will shift down into lower gear or not shift up after a stop. I had a rebuild on it about 2500 miles ago and returned to the transmission shop, had it checked and they say it’s working fine. I recently installed a new vacuum modulator is hopes that would correct the problem but it did not. I’ve checked the governor and it seems to be working as it should. I’m at a loss for what to do next and would welcome any input. Thanks.

 

[AuroraGirl]

shifting issue with TH350-Shifts great until it gets warmed up and then intermittently will shift down into lower gear or not shift up after a stop. I had a rebuild on it about 2500 miles ago and returned to the transmission shop, had it checked and they say it’s working fine. I recently installed a new vacuum modulator is hopes that would correct the problem but it did not. I’ve checked the governor and it seems to be working as it should. I’m at a loss for what to do next and would welcome any input. Thanks.

have you checked the underside and what the fluid, filter are doing? are your cooler lines kinked or restricted? THe cooler itself?

 

[Vbb199]

The modulator itself has a little flathead screwdriver bit in if to adjust shift points a little
You may want to consider looking into it, or perhaps, is there a vacuum leak on the modulator line ?

 

[Mlcdc1]

Thanks for the input. The fluid is good and there are no apparent kinks in the lines. Adjustment with the modulator screws doesn't seem to affect the issue either way. There isn’t a leak on the line.

 

[AuroraGirl]

Thanks for the input. The fluid is good and there are no apparent kinks in the lines. Adjustment with the modulator screws doesn't seem to affect the issue either way. There isn’t a leak on the line.

is it hard line most of the way? if its hose it may collapse

 

[Mlcdc1]

Has the hard line except at manifold connection and modulator cennection

 

[Bextreme04]

What's the kickdown cable look like? Maybe getting stuck?

 

[Mlcdc1]

kickdown cable is working ok. Have driven with it unhooked and makes no difference.

 

[Memaloose]

Sounds like the rebuild shop needs to take it for a drive.

 

[Vbb199]

The pump halves perhaps were never actually broken down and inspected and remachined

Its a common thing for transmission builders to conveniently forget IMO


As it heats up, pump pressures degrade due to scoured pump halves


There's a test port on the outside of the trans to check pump pressure.

1/8th npt

 

[Mlcdc1]

I had back to the rebuild shop and they checked it out and said there was no problem. not sure I’ve got enough understanding to check pump pressure myself so may find another shop and get a second opinion. After doing some further reading, what’s the possibility that the governor is failing?

 

[Matt69olds]

How easy is it to duplicate? If it’s an occasional thing, a little detective work on your part could help. If it’s fairly easy to get the trans to act up, have them drive it or have someone ride with you until it does act up. If it happens pretty regularly or is easy to duplicate, the shop should do what it takes to make it right.

Put a Tee on the vacuum line as close to the modulator as possible, put the gauge in the truck where you can see it. Drive it around while watching the gauge, that way you have a idea of what the vacuum reading should normally be. Next time it acts up, look at the gauge. If the vacuum reading are way different, you know where to look for problems.

It may be a sticky valve in the valve body. Sometimes it helps if you loosen, then retighten all the valve body bolts finger tight, and retorque them in a spiral pattern. The tolerances between the valves and the bores they fit in is very tight, it does t take much to hang up a valve.

 

[AuroraGirl]

I had back to the rebuild shop and they checked it out and said there was no problem. not sure I’ve got enough understanding to check pump pressure myself so may find another shop and get a second opinion. After doing some further reading, what’s the possibility that the governor is failing?

"nothing wrong"

If you have serious issues and its not something they could "miss" you should have said ******** or been along for the ride.

 

[Vbb199]

I vote pump degradation, stuck tv valve, jacked up modulator or substandard vacuum to it, OR the filter is clogged already (suggesting bad things)

Operational, freshly built transmissions don't miss shifts and fall out of gear when at temp

 

[Mlcdc1]

What’s the possibility of it being a bad valve body unit?