PaddycakeFTW

iTrader: (22)

I've been scratching my head for weeks over a transmission problem. Hoping you guys can help.

I bought a rebuilt 700R4 years ago from Jet Performance, back when they still sold transmissions. I opted for the non-lockup version because I didn't want to deal with wiring at the time. I had it in my old Ford behind a 350 and it worked great. No issues whatsoever.

I sold the tranny to my dad last year and he put it in his '56 Chevy, which has a very mild big block. I gave him all of the accessories I used - TV cable, TV cable bracket, everything. He installed it just like it was in my car, even with the same kind of Edelbrock carb. I had the replacement arm that goes on the throttle linkage to correct the TV cable geometry - he used that, too.

His car is now on the road and it won't shift into 4th gear - well, it SOMETIMES will, but it won't stay there. 1, 2, and 3 are all fine. Crisp shifts, no noises, no leaks. He told me it never hit 4th and I told him to stop driving around the neighborhood and take it on the freeway. I read that sometimes the internals stick when the tranny sits unused and told him to go give the car a workout. I ended up going to his place and drove the car with him - high speed, low speed, WOT, freeway cruising... The car just doesn't respond. At 50-60 mph, if I take my foot off the pedal, the car will definitely upshift from 3-4. But as soon as I give it the slightest bit of throttle, it immediately downshifts back into 3rd. Again, there is no lockup so that's not what I'm feeling and not an issue. When the tranny was in my car this didn't happen. It would shift into 4th just as well as any other gear, and stay there until I gave it enough gas to downshift, just like it should have.

I just don't get it. Our cars are set up almost identically. The TV cable is adjusted to spec, the fluid is topped off, and I just don't know what else to do. I don't want to pull the tranny and tear it apart, and I really don't think I should have to considering that I know it worked perfectly for me and absolutely nothing has happened to it since I pulled it from my car and my dad put it in his, other than sitting quietly in a corner of his shop, covered up and tucked away where it couldn't get hurt or dirty.

Any thoughts from the tranny pros around here? I've been reading up for a forthcoming rebuild on my new project and am impressed, as usual, by the expertise shared on this forum. Thanks in advance.

Eric

bbond105

I don’t think you will need to pull the trans out of the car. At most you may have to remove the valve body or governor. Are the shift points at about the right speed for the rest of the gears? How was the TC cable adjusted? If the engine is low on power and it is taking a lot the throttle to get up to speed it won’t up shift to 4th until you let off the throttle.

PaddycakeFTW

iTrader: (22)

Still hoping for some help with this 4th gear problem.

My dad bought a pressure gauge setup and we ran the car through the gears to see what was going on. Below are the results. They look normal to me, based on what I've read on this forum and others.

We also reinforced the TV/throttle cable bracket after we saw it flexing a little bit when we hit the gas pedal. Nothing changed as far as shifting but now I know for sure that it's not causing any issues.

bbond105: The 1,2,3 shifts are all good. They happen at the right speeds and feel normal. Downshifting from 3-2 and 2-1 are good as well. The car is running great. I can't imagine it's a lack of power - it's a 454 with aluminum heads and a few other goodies. It's definitely making more power than the 350 I had in my car with this transmission, and it shifted into 4th just fine.

All further thoughts/ideas/advice are appreciated. Thanks.

Gear/PSI@idle, TV connected/PSI@idle, TV disconnected/PSI@high idle full TV
Park/90/60/150
Rev/125/100/240
Neu/90/60/150
4/80/60/150
3/80/60/150
2/120/120/120
1/120/120/120

bbond105

Where pressures where taken with the car sitting still and you just placed the shifter in each gear? When taking trans pressure readings you need to be driving the car and have the trans in the gear you are taking the reading of or have the car on jack stands and have it in the gear to be tested.

It sounds like you have a valve stuck in the valve body. You can remove the valve body with the trans still in the car and check for any stuck valves.