I am having a problem with the TH350 in our C Prepared Firebird. Lately, even when I have the shifter in low (B&M QuickSilver, I think), after the car rolls off the start line about 100, or so feet, it will upshift on its own. At the last event, it upshifted, and I continued to make my run in 2nd gear. After the run was over, and I was returning to grid, I pulled the shifter back, and it ratcheted down into 1st! So it seems that the transmission is somehow shifting into second _mechanically_, that is, the selector is moving without any actual movement of the shifter by the driver. I do seem to be able to hold it in 1st. by putting pressure on the shifter, but that is very distracting.

I got under the car today and had a look around. My thinking was that we may have messed up the adjustment by running over a cone. Well, things seemed okay underneath. The shifter was putting the transmission solidly into 1st, and well onto the detent. I did adjust it a bit (no more than a mm, or two), but I doubt this made any difference. We will see at the next event.

Any other ideas on how the transmission could be shifting itself? Thanks for any ideas.

 

Wow. No one has any thoughts, or ideas?

 

Well, right before my 700R4 fried on the roadcourse it was shifting on its own like that. Do any gears slip when you hammer it? I'm guessing something internal.

 

They are supposed to do that unless you have the manual control version of the shift kit. When governor pressure over comes TV pressure the trans shifts regardless. The way the aftermarket kits work is they dump the governor pressure before it gets to the shift valve keeping it in the gear you have selected indefinately.

 

Crazy,

No, no slippage, only tire spin. :-) Thanks, though.

Fast,

I think the PO said the tranny had a shift kit in it, but that it would still upshift. Odd that it doesn't seem to do it consistantly. I mean one event it will upshift at about 3500 RPM, or so and another event, it will bang off the 6000 RPM rev limiter. Guess I just need to get a shift kit and do it. Are any better than others? Thanks.

 

Well my TH350 is bone stock, no shift-kit installed yet, and if I put it in 1st gear, it stays in 1st gear, it does not shift on its own. I know this for fact because I refuse to shift it on the roadcourse until I install a shift-kit and raise the line pressure. So I've only been using first gear to drift for the past 6 months, from idle to 5.5-6K it stays in first.

 

I was also told it could be an issue with the governor. I haven't had a look at it yet. I will probably pull the cover and have a look when I install the new torque arm.

 

When you install the Trans-Go Performance Shift kit. it will give you the spring to lock out the overrun feature. This will allow you to hold 1st gear to any rpm without it shifting to 2nd gear on its own.

 

install a stiffer 1/2 shift valve spring,a lighter weight governor or increase modulator pressure

 

when you have the transmission pulled into manual low, it should stay there, the only way it should go to second is if the gear selector inside the tranny is in second, therefore, your shift cable is out of ajustment either due to hitting something, cable stretch, or vibration. same thing happened to my buddies nova. it actually took alot of adjustment to get it right.

 

Yeah, I can't help but think that, too, but the shifter looked like it did pull the bellcrank on the tranny nicely into low.

I do remember way back when I had a 77 T/A that they had problems with the car actually using the shifter cable as an alternative ground causing the casing to get soft and stretch, causing a lot of shifting issues. The fix was a 'kit' with an extra ground strap that went from the tranny to the body and a new cable. Although I don't see any problems with the cable, I may try a new one of these, too.

Thanks, all.

 

Can I also adjust how harshly it shifts? I would really like to keep from hammering the rear tires when going into second. It makes for some fun turns when you shift while turning, which happens most of the time in Solo II.

Thanks.