350 transmission

[HotRodPC]

Sorry if I was being confusing. It's the 350 Transmission it has the vacuum module on the side of the transmission it was leaking transmission fluid so I had it replaced when I pull the vacuum hose off of the modules it leak transmission fluid that's why I replaced it

OK, now we're getting somewhere. So it's certianly NO 700r4 and is a Th350. So this leak, was it the modulator itself leaking at a seam, or was the fluid in the vac hose being sucked into the engine, or was it the O ring where the modulator goes into the case?

 

[Randy Terry]

No I haven't had it but a couple of months but it just felt unusual because I had in 86 model that had to 700R Transmission in it. I would say when it goes from 2nd to 3rd it probably drops RPMs but I don't have an RPM gauge

 

[animal]

Exactly what I'm thinking, and he's thinking the lock up he feels is a **** to OD.

If the truck "*****" to OD then Shaky has MUCH bigger problems.

 

[Randy Terry]

When I took the hose off of the module on the side of the transmission fluid came out I was told the diaphragm in the module may have been worn out so I needed to replace it, you have to get under the truck towards the rear of the transmission to get to the module.

 

[Randy Terry]

It's a 3-speed transmission, it doesn't have OverDrive.

 

[HotRodPC]

Probably another easy thing to check just for ****'s and giggles is the governor. The governor is inside the round cap on the driver side of the transmission. I wonder if the governor valve could be hanging up.

And there is no electric plugs ins going to the transmission at all right? And you don't see any place where an electric plug would even go on the drive side of the case?

And did this problem start right after you changed the Vac Modulator? Or did you change the modulator thinking it would correct this problem?

 

[Randy Terry]

I change the vacuum module thinking it would correct the problem because it was leaking fluid at the module .

 

[HotRodPC]

When I took the hose off of the module on the side of the transmission fluid came out I was told the diaphragm in the module may have been worn out so I needed to replace it, you have to get under the truck towards the rear of the transmission to get to the module.

Yes, that's true. If you got fluid out of the vacuum line the diaphram had a hole in it and it was sucking trans fluid. You may have even gotten some of that into the engine and you should have seem some white smoke. No worries there though. It may have been just a tiny pin hole and not enough to notice. All it would do is lube your valves real good and burn off so no harm to the engine.

 

[Randy Terry]

When I drive slow that's when it shift from 2nd to 3rd fast, but if I take off fast and keep up the speed it shifts fine.

 

[HotRodPC]

A Th350 isn't as dependent on the detent cable adjustment as the 700r4 is on the TV cable. So that wouldn't cause this problem. I just wish I understood better what you mean by it feels like it shifts into OD. Hopefully @74 Shortbed may have a better understanding. If I was guessing you're saying it's bogging down or dragging. If that's the case, that leads me to believe when it goes from 2nd to 3rd, there's a valve that's not moving all the way as it should and you're getting a bleed to where it's kind of hanging in 2nd and 3rd at the same time.

 

[Randy Terry]

Yes that sounds like the way to put it when it goes from 2nd to 3rd when driving slow when it goes in the third it kind of bogs down, but when you accelerate fast and keep up the speed it shifts 1st 2nd 3rd just fine

 

[HotRodPC]

When I drive slow that's when it shift from 2nd to 3rd fast, but if I take off fast and keep up the speed it shifts fine.

So there's 3 things that determine shift points on a Th350, Vac Modulator, Governor and detent cable adjustment. It'll shift fine without the detent cable hooked up, it'll just shift very early and no kickdown whatsover. If Vac modulator is unhooked it will shift very late but will eventually shift with the governor overrides the vac valve. If the governor is hung it probably won't shift at all.

When was the last time you've done a fluid and filter change? So if you're take off like half throttle or better it shifts fine, if you take off slow then it's 1st to 2nd Ok, but 2nd to 3rd has problems? Whatever this is, it's not a common Th350 problem. We should wait for Art to get here. Sometimes 2 guys are better than one, or I'm overthinking or overlooking something.

 

[Randy Terry]

I don't know when the last time the fluid has been changed. If I take off at half throttle it shifts fine, if I take off from a dead stop fast it shifts fine, if I take off from a dead stop slow first to 2nd shift good but second to Third shift fast and bogs down.

 

[HotRodPC]

OK, I think I'm getting it now. It's not like it's going into OD, I think understand what you're saying now. You sure you can't get any more adjustment on the detent cable? And, turning the screw inside the new modulator clockwise about 1/2 turn may help too. I'm beginning to think you just don't have any throttle pressure at all at low throttle so it's shifting early, way early. That would be the only thing I could thing off of hand.

 

[Randy Terry]

Okay, thanks I will try that and see what happens thanks for the info.