crene67ss

I have a 700r4 tranny that's acting up. I added a B&M shift kit and a billet servo. The tranny kicks nicely and shifts to 1st and to 2nd with no problem. But after going to 3rd and 4th, it all of the sudden looses pressure. From then I have now removed the mods of the valve body, rechecked the servos seals. I have preassure checked the whole tranny and everything checks. I have even adjusted/ replaced the passing gear cable several times. If anyone has had similar problems or know on how I may be able to resolve I would gladly appreciate it.

Any help is appreciate it, thanks in advance... Rene.

crene67ss

Hello, again. I forgot to include that the transmission was overhauled with not even a mile on it. Also, when I said that it looses pressure, the rpms will start from zero winding up and shifting to 4th. On 4th it does the same thing.

Thanks... Rene.

MadMax350

Well, this may not be the appropriate "advanced" reply, but did you check the basics:

Is the fluid level correct?
Is your filter seal tight and not ripped?
Has the transmission front pump been overhauled?

How do you know the trans is loosing pressure? Do you have a pressure gauge hooked up to it and if so, where are you hooking the pressure gauge to on the trans?

700r4/4L60-E trannys have a common problem in 2 areas that result from shift RPMs occuring over 5500 rpm or so...

1) Even a full fluid level could run low at WOT and high rpms causing a temporary pressure loss. I experienced this problem after the weather turned cold here and actually had to overfill the trans by about 1 pint to get it to shift correctly into 3rd gear.

2) The front pump slide spring in 700s and 4L60-Es needs to be upgraded in any application that sees shifts higher than 5500 rpms to help maintain pressure. If your front pump is stock, and you are pushing these high RPMs, you might need to look into this.

OneFlyn95z28

Max has some good info there. Along with it I have a question and some info

Does it do it at WOT only?

DID you change the seperater plate?

There are some(starting to get forgot about) issues that can cause this if you use the wrong VB plate. ALL the new GM replacement plates need to have a Line Bias valve changed in the VB to match them. MANY do not know this. It will cause a lose of Pressure at WOT because of a double bleed happening.

I hope you find a solution soon

crene67ss

Thanks for responding Max and Ellis:

Thank you, for helping with this problem at hand. Yes, the tranny was check with a pressure gauge, aswell as air checked to see that all of the gears are functioning properly. I have identified the problem and have successfully resolved it. A piston inside the valve body was getting stuck, causing 3rd and 4th to loose pressure. So I decided to remove all pistons and springs from the valve body and clean it up with solvent. I noticed a piston in the valve body that didn't want to come out so I began cleansing the valves. After washing all parts I put it all together, added oil and took it for a spin. Everything was working fine. All gears are going in when they're soppose to. Thanks for your help guys I really appreciated it. Thanks once again. Rene.

OneFlyn95z28

Glad you got it going. You will have to forgive me for not mentioning to clean the VB. I just took it for granted it had already been done

Good luck!