[mjk11]

I,ve got a rebuilt TH350 that works fine in drive gears. When the chevelle is on jack stands, reverse works fine. When I put the tires to the ground, it does not go in reverse. You can feel the trans engage when shifting to reverse, doesn't move, will actually roll forward if I let off brake. I'm scratching my head and very frustrated. Any help would be great.

mike

 

[larrie]

Hi Mike,
I'll assume the fluid level is good. If you are positive you can shift into and hold high gear then try this.
Take off in 'manual low' keeping it in low accelerate and back off the throttle. Do you have engine breaking or does it free wheel(feels like neutral).
Larrie

 

[mjk11]

Hi Larry,

Fluid level appears fine on stick when I check. As for low and breaking, I will double check and get back to you.

Thanks

Mike

 

[mjk11]

Larrie,

Well, I tried running it up in 1st to see if there was any engine braking and i seemed if there was. I adjusted the linkage by the shifter, got a little improvement and then things went to hell. Smoke started coming out from under car so I shut it down. Looked under the car and a huge pool of trans fluid was there. The "modulator" where the vacuum line attaches to blew off. Is this done for or could this have been the problem and is fixable? I attached a pic.

 

[larrie]

Mike,
Isn't high performance fun ..lol ... Is the clip that holds the modulator in bent, loose or missing ...?

 

[mjk11]

Larrie,

High performance is great..... when it works! I have a buddy that is a chrysler tech that helped me build the motor and it is rock solid. But, he has no idea on the th350 as he is to "young" training wise to know the 350 trans! is this an easy fix, or should I take it in? The place I had rebuild the trans is no longer in business, go figure!

 

[larrie]

Mike,
First of all we have to determine why the modulator valve blew out. Like I said was the retaining clip & bolt installed which holds the modulator itself in the case. Second .. and I don't mean to be insulting with my questions but are you absolutely sure you have a 2-3 shift.... explanation ... the high clutch drum is also engaged when in reverse.... also there are a set of clutches in the back of the case .. which are called the low/reverse clutches.... clutches are applied when reverse is selected or when manual low is selected to provide engine braking and extra holding power in man low. ... when 'D' is selected low gear is achieved via a one way roller clutch installed in the centre support.
So .... if the mod clip is good and was tight and not mangled ... then an EXTREME spike in the line pressure MIGHT blow the valve out of the case ... but I have personally never seen it as there is a bypass valve in the pressure regulator system that releases extreme pressures.
So let me know if the clip is ... whatever ... and we'll take it from there.
Larrie

 

[Schurkey]

Finding out about engine braking will be crucial.

First Guess: No engine braking in L1. Roasted Low/Reverse friction. Drive works only because roller clutch engages, takes the place of Low/Reverse.

 

[mjk11]

Here is something that might also help with this. Why would the car "lurch" forward when put into drive if I have a 2600 stall installed? I an very knowledgeable on the whole trans thing, but I was under the impression the car should not really start going until it hit that rpm range. Also, the trans would not shift though the gears while in "D" when the car was on jackstands and engine was brought up to 4000 rpm. Is this a good time to possibly doe a 4 speed swap!!

Mike

 

[larrie]

Mike,
You still have not mentioned whether or not the modulator was bolted down... a loose modulator would cause all of these symptoms.....as for stall speed ... it will flash to the max rated stall ... not actually rev to 2600 before moving the car.
Larrie

 

[mjk11]

Larrie,

As for the modulator being bolted down, I am not certain. I "assumed" it was ready to bolt in and go from the shop, but we all know what happens when we assume! I do know that I could freely rotate the modulator by hand if that means anything. A loose modulator could affect the reverse issue? Is this a fix where a new modulator can be installed, relatively easy and fix this?

Thanks for the help.

Mike

 

[larrie]

Hi Mike,
I had another look at the pic you posted and zoomed in on the clip ... difficult to see if the 2 little fingers of the clip are broken off .. but ... I can see the shoulder of the clip bolt .. unless you backed it off it looks like it is NOT torqued down... besides the point that the lock washer is on the wrong side of the clip