Fun71

So I chose to have the TH350 rebuilt instead of doing the TH200-4R swap. Seemed easier and quicker, plus I don't do long distance driving so not really any compelling reason to do it.

Now with the rebuilt trans the WOT 1-2 shift (in D) is too late; about 500 RPM higher than it was previously, and the light/mid throttle 1-2 shift is too soon. I told them I liked the way the trans shifted before and I wanted to keep the same governor and shift kit, which they said they did (same shop that rebuilt the trans 15 years ago, told them the same thing back then and everything was the same after the rebuild). They claim it's the same governor, and I tend to believe them since they are willing to get a governor recalibration kit and play around with it until the WOT 1-2 shift is where I want it for no extra charge.

So I am not understanding this. I have some knowledge of TH350s (rebuilt one in college and installed several shift kits) but I don't understand why the shift points are now so far off with the same governor. Just for fun, they put my old vacuum modulator back on and it didn't change anything, so now we're on to playing with the governor weights and springs.

Anyone with knowledge of TH350s have any thoughts on this?

Don R.

I'm no expert but I remember the TH350 uses a TV cable in addition to the vacuum modulator. Be sure the cable is correctly adjusted, and I would put a new modulator valve on it.

coppercutlass

The tv. Cable does not affect upshifts . The gov. Calibration will affect it at w.o.t. the modulator will under load since it uses a vacuum signal there is no vacuum at w.o.t . Another thing to think about is the 1-2 accumulator . Some shift kits specify to leave the spring out perhaps they put one in thinking it was left out ? The spring on the 1-2 accumulator will shoften or delay the shift . The modulator controls line pressure changing the pressure changes the shift points.

Fun71

No TV valve on a TH350, just a downshift detent cable that is an on/off switch. No adjustment needed as it works fine, the trans downshifts when going WOT.

New vacuum modulator was installed, they even put my old adjustable one back in for grins and no difference in operation.

Yeah, I think they mis-communicated about retaining my shift kit. When I installed the TransGo shift kit way back when, I left the factory manual low control spring in to retain the factory lockout provision that prevents a manual downshift above a certain sped/RPM. Now the trans will downshift at any speed, so I know FOR CERTAIN that they changed it.

Problem is,they are adamant that they used my original governor and shift kit. I have asked directly multiple time, both the owner and his main man, and both repeatedly said it is all the original stuff.

Fun71

I drove the car around this weekend and figured out the early 1-2 part throttle shift didn't change at all with varying throttle. Every time I took off from a stop, it shifted at 12 MPH (unless I pushed to the point the downshift cable activated). It seemed as if the vacuum modulator wasn't having any affect at all on shift points, so I pulled the vacuum line to the modulator and went for a test drive.

It shifted 1-2 at 12 MPH when I left the driveway. I drove around the neighborhood and every time from a stop, it shifted 1-2 at 12 MPH, no matter how much throttle I gave it (below the kickdown point, that is).

WTH? In the past, every time I forgot to connect the vacuum line it wouldn't shift out of 1st until letting off the throttle completely, and it dropped back into 1st at the lightest touch of throttle. It is definitely not doing that: 1-2 shift at 12 MPH and it stays in 2nd with moderate throttle application.

So maybe the modulator valve inside the valve body is stuck? If so, I wonder if that has any impact on the line pressure and therefore the WOT shift point?

coppercutlass

Well the modulator valve is easy to get to just might be messy . Now another thing to think about is the manual valve adjustment . I belive it has to be flush to a .025 varience between the manual valve and the valve body. I would be looking at the modulator because it distributes fluid to the pressure valve , detent valve , and the shifting valves. But the fluid has to go to it first and then from there it goes to those 3 . So if pressure regulation fails at the modulator it suffers elsewhere.

1970-W30

Kenneth, my offer still stands, and thats with a no questions asked money back guarantee ..........

Fun71

Good info.
I remembered something that supports the theory of the modulator valve being the issue: back in high school when I installed my first TransGo shift kit, I accidentally put the spring on the wrong end of the modulator valve (between the vacuum modulator and the valve instead of pulling the valve and putting the spring on the inside end). I remember that caused the WOT 1-2 shift to occur much higher than the factory 4800 shift point, like around 5400 RPM. Same thing I have going on now. Hmmm...

That has definitely been in my mind. If I can't get the shop to correct this then that is my backup plan.