Hello guys !

Didn't come on the forum for a looooong time, sorry about that.

I have a problem with my TH700R4 gearbox.

Last year, the gearbox failed : Burnt 3-4 clutch pack (pretty usual), and the splines separated from the main body on the sun shell.

I took profit of the rebuild to ask the guy that did the rebuild to upgrade the gearbox a little bit. Here's the list of the mods (as far as I know).

* Front pump upgraded to a 10 vanes rotor.
* Front pump pressure spring upgraded for having much higher internal pressures.
* All clutch packs replaced by Alto Red clutch stacks.
* 2-4 Servo replaced by a Sonnax assy (2nd gear super hold assy Part No. 77911-03K and 4th Gear Super Hold Dual Servo Kit Part No. 77767K)
* Reinforced brand new Sun Shell.

That's all I remember so far.

The gearbox got reinstalled in the car (a 1988 IROC with a stock 350 TPI), but I have some problems.

1st and 2nd gear just work fine, as well as reverse and neutral. However, I almost can't shift to 3rd gear unless I'm driving at high speed and high rev in 2nd, hit the gas pedal to the floor, then release it. 3rd gear then comes in. Never tried to do the same in 3rd to see if I can get the 4th gear to come in, as the 2-3 shift is pretty rough.

I checked the line pressures, and they seem fine according to the guy that rebuilt the transmission. I also checked the setting of both the TV cable and the shift selection cable, and both are fine. Also checked if the governor was OK, and it obviously is.

The guy that rebuilt the tranny give me technical assistance, but we are now running out of ideas.

Is there anybody on this forum who would have any other idea for troubleshooting ?

Thanks in advance for your help !

 

It does sound like an issue with the throttle valve, though.
Rough shifting at high rpms is exactly what a maladjusted t.v. cable will cause.
As you have already checked that part, perhaps the valve itself is sticking somewhere in the valve body.
I don't think there's anything wrong with the clutch bands or packs, as you seem to be acutally moving and the trans is shifting after all.

 

Thanks for your answer !

Just for info, once the pan is removed, is there an easy way to remove and inspect the TV Valve components (sleeve, spring and the valve itself) ?

Another question : Is there any kit that would improve this function of the gearbox ?

Thanks in advance for your help !

PS : Sorry if I make some mistakes in my english, this is not my mother language

 

Dude, look where I'm from. No need to excuse yourself
You're welcome, btw.

I'll have to pass on whether you can access the valve without removing the transmissions insides. Never had to do it before.
There are shift kits, though, which will replace said valve and give our firmer shifting action and different shift points, depending on the kit.
Let's wait for someone to chime in, who has in fact done such a swap in the past.

 

Contact Dana at Pro built Transmissions here on 3rd gen he knows 700R4 is inside out

 

700r4 yes you have to pull the VB to get to TV and componts Just watch your check ***** if they do fall out plenty of info on getting them back in.

 

I meant to say yes on inspecting, With pan off. if you remove the VB just watch were check ***** go. I think there is 3 or 4 in VB