65 rivi w/425 super wildcat, transmission question...

[Guest onedesertdog]

Hi all,

I'm having a transmission problem that I'm hoping someone will be able to point me in the right direction.

New fluid, filter, gasket etc. It won't shift in D. Stays in first. It will shift all gears manually. I did some searches and read about switch pitch and Modulator.

I had rebuilt the carbs, (and it sounds sweet) and rechecked to make sure all vacuum lines, and linkages were hooked up. Reading about the modulator, I checked and found that the rubber hose had come apart at the tubing to modulator. I replaced and connected it, but no bueno.

Thanks for your help,

Buddy

[john hanson]

Try replacing the Vacuum hose to the carb. If it is blocked it will cause to shift at higher speed and hard.

John Hanson

[Guest onedesertdog]

Thanks for the reply. It actually did do that once while testing out the carbs.

I'll take off the hard metal line from carb, and rubber hose at modulator and check that out. The hose at the mod. was all gookin puckied, and soft. Could the modulator be plugged, and if so can I remove it to clean?

Thanks,

Buddy

[RivNut]

Once the car is in drive, will it stay there? The modulator controls upshifts. If the modulator is bad, it will not stay in the higher gears. It's either a cracked/plugged vacuum line to the carb or you just need a new modulator. Take a loooong piece of vacuum hose and bypass the steel line. See if the trans will shift and hold the high gear. If it still won't do it with new vacuum line, then replace the modulator. Check the steel line for cracks, or pinches too.

[Guest onedesertdog]

Thanks.

I'll go check those items first. Hose, steel line, bypass.

In auto, right now, it won't upshift out of low. Manually, I can shift L1 Up to L2 and then 3rd. ok.

[Guest onedesertdog]

I checked those items and nada. So I guess I'll go get a Modular valve.

Thanks for the help,

Buddy

[RivNut]

You might also ask around to see if there's a reputable transmission shop that you could get to. They might be able to diagnose it for you on a test drive. If it's not the vacuum modulator, you might not be out the price of a modulator you don't need. Most good shops will do a test drive and diagnosis for no charge. From there you can make up your own reasons for doing it yourself or having someone do it for you. Remember, it's been a few years since that style TH400 has been built. If there's an older guy in the shop who's been doing transmission for quite a few years, you'll probably be in good hands.

Ed