I have a 4R70W tranny, was accelerating from a light and then all of the sudden the engine revved up and the truck wouldn't go. Now I notice that it starts out fine in 1st and shifts to 2nd, but after that when it shifts into 3rd the engine just revs. If I push the OD off, then it just shifts from 1st into 2nd and stays there, won't even shift into 3rd. Any ideas??? By the way, I have a Transgo shift kit which I installed about 7-8K miles ago.

 

Is the transmission simply not moving beyond 2nd gear, or does it rev high and then shift into 3rd when you take your foot off the gas???

To my knowledge, there is a 1-2 Shift Accumulator Piston and also a 2-3 shift accumulator piston. The 3-4 shift is handled by a valve inside the valve body. The 1-2 & 2-3 accululator pistons are inside the transmission, rather than the VB.

Since you did the Transgo install, you can answer this question: The 2-3 Accumuator pistion is inside the transmission. It's located at the back, on the passenger side. This piston is pressed into the transmission, followed by a sping and then an aluminum disc. Did the disc and spring fall out when you removed the VB??? I ask because when I had my VB out and the disc fell out, I reinstalled it the wrong way. The cone on the disc needs to face down, and is held in place by the VB itself. My truck shifted fine for a few days, but after a few WOT shifts, the 2-3 shift began to slip. I removed the VB and turned the disc around and haven't had a problem since.

That's one possibility.

Another is that the VB is not holding enough pressure to make the 2-3 shift. Did you use a new VB gasket and properly torque all of the bolts in the correct order when it was reinstalled?? This is very crucial. If the VB leaks, you can bleed off pressure and not have enough for the shift.

Another possibilty is low fluid or a filter that is not properly attatched to the VB. Could also be that he rubber gasket on the filter came off and is pressed up inside the VB. A loose filter or low fluid will both cause the transmission pump to suck air. If air instead of fluid is passing through the VB, you won't have enough pressure to make the shift.

 

The tranny does shift beyond 2nd, but whenever it does, just the engine revs until I slow down and it downshifts back to 2nd then it's ok. I'll pull the pan and check all the things you mentioned above. When installing, I did change the gasket and torqued according to specs. I'm just praying that the tranny's not shot!!

 

I pulled the pan and found that the seal on the 2-3 accumalator was chewed up, I replaced with a new one and reinstalled the VB with new gaskets. Still doing the same thing. Runs only in 1st and 2nd, once it shifts again, only the engine revs and the truck won't go! I have to coast until it downshifts to 2nd again. Any other suggestions?

 

It sounds as if the 3/4 (direct) clutches may have sustained damage because of your accumulator seal failing.

 

I was afraid it was something major!! Does the trans have to be totally rebuilt or is this something specific that can just be fixed so that it doesn't cost me my right arm? Truck only has 24,000 mi.

 

It's tough to be 100% sure from 3000 miles away, but it sounds like you have trouble. I know it's a hard pill to swallow, I deal with this every day- most people don't WANT to fix a transmission, but they NEED to. With your low milage I suggest that you get it checked out and have it fixed right- if it needs it.