Hi,

Following on from my last post. I have jacked the car up and run through the gears. 1 to 2 to 3 changes only happen at 4000 rpm.
I do not get a 3 to 4 change at all. TV cable is adjusted fine and working and I have changed fluid and filter. Following on from a suggestion I have removed and cleaned the governor. All seems to be OK. ( Should I have one weak yellow spring and one stronger purple spring ?) Gear is fine. I am really stuck now. Could it be due to a sticking TV exhaust ball valve and how difficult is it to remove the valve body with the tranny in the car?
I am in the UK so details here are difficult to find. the car was running fine one day then this happened. I have the GM manual for the car.

All suggestions would be most welcome

Thanks Guy

 

Sounds like a sticking TV valve. You can remove it w/o taking the valvebody off, so it's a little easier.

You just remove the pan, and cable from inside. Remove a bracket and a pin inside the TV housing. Remove the TV plunger and spring. You can then tap the TV valve inside with a screwdriver.

This site has a GREAT explanation and help for how the TV works too...

http://www.tvmadeez.com

Tom

 

Thanks Tom - I will give that a go

Guy

 

Last time I checked, 700R4's don't shift into 4th at WOT. They aren't supposed to, they never did and never will.

 

Thanks,

The car wont shift into 4th at any throttle opening not wide open.
I have just taken out the valve and checked everything as suggested. The valve can move OK and I have put it back.
Can't test yet as I need to refill the trans and it will be Wednesday before I can get the fluid.

 

Last time I checked, the B4C cars did, still do, and always will.

 

Yeah the B4C cars are not the same as the rest of the 700R4's. Because the cars needed to go really fast to catch the bad guys, they got a special modified upshift valve that allowed shifts into 4th at WOT. The rest of the 700R4's (inc the 1LE cars) won't shift into 4th at WOT. Here it is straight from the technical articles of this website:

Why won't my automatic tranny shift into overdrive at wide open throttle?

A: It's designed not to shift into overdrive if your foot is all the way to the floor. You must be at 2/3 throttle or less before the tranny shifts into OD. So when you hit the top of 3rd gear, you'll have to let off the gas to allow for the shift. But putting your foot back into it will probably cause a downshift resulting in the same problem.

B and M makes a kit modified kickdown valve (part # 70237) which fixes this problem. It costs about $30 and can be ordered through the Summit or Jegs. GM also makes a modified upshift valve which it included in police packages and that part # is 8673948 and sells for around $15. This will allow the tranny to shift into OD at full throttle.

 

I have just refilled the box and tried again with no success unfortunately.

Car still only goes 1,2 3 at WOT.

I guess I am going to have to get someone to take a look at the box.

Can someone confirm that the only connection the 700R4 box has with the outside world is the TV cable and that there is no electric trickery involved !

I assume the wiring harness is purely for the lock up. Am I correct?

Guy

 

Did you read what I posted? B & M makes a kit modified kickdown valve (part # 70237) which fixes the problem of the 700R4 not shifting into 4th at WOT.

 

what Guy is trying to say is that his trans. will only shift @ WOT, not @ legal street speeds.

 

Yep, tcc only. The newer thirdgen's also have vss wire, but being an 87 yours is cable driven.

Let us know what the problem is when you find it, I'm curious to see what it is

 

Hi, Thanks for that.

I can't get 4th at all. The only gears I get are 1 to 3 with changes at Wide open Throttle. Certainly makes for interesting driving!

Guy

 

Well a trip to my local trans specialist had it sorted in no time.
He has a machine which flushes the system and cleans out all the rubbish. It took 19 litres of trans fluid and a couple of hours but I had all the gear changes back just as before. There was no damage to the box at all and the pressures were fine so it was something in the valve body.

I am one happy Z28 owner now!

Thanks for all the help and suggestions.

Guy

 

i know that part # the tech articial gives as the fix to get 4th at WOT but it's the incorrect fix. Trust me I installed it. B&M 70237 and GM 8673948 only give you 4th gear at 2/3 throttle and less. Not WOT. I've had a hard time tracking down the correct fix but heres the correct part # for those looking B&M #70249 its $118.00. that part # will give you 4th at WOT.....