What makes the trany shift at 2800?
 

Hello
I just got my 78 running great but the tranny likes to shift
at 2800 rpm in all the gears?
What would cause this and is it fixable???
Thanks again!
:hi2:

My guess is the shift modulator. Its either bad or the hose came off. Its mounted on the RR corner of the trans. Easy to change out & some can even be adjusted. Pop the hose off & turn the screw inside of the fitting...corn

or the TV cable is mis-aligned.

Which model are we talking about, 350, 400, 700?

I would say th350 maybe th400 being a 3/4 ton.

Sorry its a 400. I'll look at the mod. How can you tell if the shift modulator is NFG??
It shifts real strong but at 2800rpm??

That to me sounds a little more like the governor is sticky or worn out. Does it always shift there or does it change? Modulator valve might play with it a little bit. Usually that's we it wont shift out of 1st until the rpm is really really high like a WOT shift.

Alwas shifts at 2800! Very hard bam shift like it was a preformance tranny?

Have you checked the fluid level? There might be a small flat head screw in the modulator valve you have to take off the vacuum hose off it. It will be in the center of the hole, need a pretty small flat head screw driver to turn it. Some have them some don't. If there is turn it in to raise the shift points a little more and out to lower them. You can turn it all the way in but that will always make it shift very high and will not shift unless you reach that high rpm and it will stay like that.

Do you know what your rear gear ratio is and what size tires you run?

The tires are 30" and the rear end is 78 stock.
Fluid is topped up. I have to locate this Mod valve.How do you know if the
valve is good?

There will be transmission fluid coming out of it, they arent that much to replace (20.00) if it does need replaced. Take the vacuum line off and see if it shifts different. If the transmission is a th400 the modulator valve should be on the passenger side where the transmission cooler lines are, right above the pan.

If you need a picture I can post one.

mine was doing the same thing it would rev up around 3000 then SLAM into gear, Looked underneath and the modulator wasn't hooked up! Mod valve on a th350 is on the pass side with the hose coming off it to your intake

Thanks guys I'll let ya know as soon as I dig it out of the
20' of snow!
where the he!! did I put that 4X4!LOL