I read quite a bit of information on how TV cables work on the 700R4 trannys and in specific my 1990 corvette. My tranny guy told me to go ahead and adjust my cable 1 or 2 clicks toward the front of the car (so it would be making the cable longer or looser). I have already checked and it would appear that the cable right now is in the correct preset position to where it should be. Being my tranny guy rebuilt the transmission I have to trust him when he says to go ahead and move it a click or two. The primary reason he told me to go ahead and do this is because I told him that the car is shifting too late at WOT in first to 2nd gears. I mentioned to him that I believed the cable didn't affect WOT and only did part open throttle positions and that the govenor adjusted WOT and why not just change the weights and/or springs in it. He said no no no. NO adjusting of the governor is needed and that he felt it was working fine. He once again told me to just adjust the tv a click or two.

So my question is. Who is right? After all the reading I did on how the TV system works I can see it affecting everything and not just part open or WOT conditions.

How much of an impact does moving it 1 or 2 clicks looser make on the tranny? I don't want to blow anything up down the road, but want the car to shift earlier then it is at WOT. Being I don't have any special guage to check TV pressure at the tranny after I adjust it the 1 or 2 clicks, I have no baseline to go by if I have moved it too far or not. I told my tranny guy this as well and he didn't seemed very concerned by it. Said don't worry 1 or 2 won't hurt. Is he right?

Please help, Iam not gonna touch this thing, I wish he would, but it appears he might be fed up working on it. I dunno really what to do.

Jeff

 

1 click either way is acceptable, in my opinion. If the cable is old, a new oem tv cable is money well spent. If any doubt, attach a guage to the side of the trans and read the tv pressures with the guage. This will confirm a possible problem, if there is one.
The purpose of adjusting the cable is to make it as tight as possible while not moving the internal tv valve. Slack, generally speaking, is bad.

 

Back before I knew any better, I tried adjusting the cable. However it seemed only effective at softening the shifts, at WOT or part throttle. It had little or no effect on the speeds at which the shifts took place. I learned a loooong time ago that an up shift takes place when the governor pressure over comes the throttle pressure. The lighter your pressure on the gas pedal, the easier (lower speeds) it is for governor pressure to exceed throttle pressure, as throttle pressure is lower at lower pedal pressures. At WOT you have a predefined throttle pressure (gas pedal to the floor), therefore it is most effective to recalibrate the governor. The problem with adjusting the TV cable is that the adjustments are "global", effective at all throttle pressures, and that at light throttle, there may not be sufficient pressure to achieve complete, slip free shifts. Slipping heats up, wears out, and shortens the life of the transmission. Of course, through out all of this, I defer to Pete K.

RACE ON!!!

 

Nope, that hits the nail squarely on the head

 

HEY! That's one in a row.

RACE ON!!!

 

Good informatin above, what do you deem "to late" for a 1-2 shift?

There is no "preset" TV position, the unit is overhauled, installed, the TV is pushed full back and the pedal is smashed to the floor setting the cable length "near" correct. For 90% of the vehicles, that's fine, tweaking it a few notches, especially looser after an initial smash carries no dangers.

After tweaking it, play and see where your WOT shift is now, but remember, you haven't stated what late it, if it's near redline, it's not late, maybe later than you wish, but not late, and as mentioned, you will need someone a bit more savvy than an average AAMco type tech to know and have the spare springs and such to tweak a govenor into a TV pressure.

When lengthening a TV cable, pay particualar attention to drawn out and lazy shifts, specifically 2-3, the 700 is not only releasing a band, but applying a clutch pack on that shift and lazy shifts due to lax TV pressure signals in the valve body can be a long term death sentence. But again, a click or two either side is not abnormal.

And remember, while he should take care of it for you, techs do not generally overhaul a unit, then go bang it to check WOT shift points. They check for all shifts on the lift, then take it out for a quick run looking for issues in normal driving conditions.

 

Read the following link and that should answer your questions.

http://www.tvmadeez.com/article/index.php

I use a 300psi guage with a 6 foot hose on it to set a T.V. cable.There's a plug on the drivers side of the trans case just above the linkage.Thats where I get my pressure reading.At idle presure is about 75psi.You want to adjust the cable just a hair short of making the pressure rise.Hope that makes sense.

 

Shift speeds are as follows after todays test runs.

Under 1/8 throttle

1st - 2nd at 10
2nd - 3rd at 25
3rd - 4th at 42

Under 1/4 throttle
1st - 2nd at 15
2nd - 3rd at 42
3rd - 4th at 55

Under 1/2 - 3/4 throttle
1st - 2nd at 45.....Shift held 40-45mph or 4700rpms for 2 seconds.
2nd - 3rd at 80
3rd - 4th...stopped before

Under WOT
1st - 2nd at 50 Shift held 50mph or 5200rpms for 2 seconds.
2nd - 3rd at 85
3rd - 4th stopped before

I basically did this for this time only, usually when the car starts winding out as bad as this I get off of it.

Jeff

 

what do you all think?

 

*I* think you need to recalibrate, or a different governor. As *I*, and others said above, playing with the TV cable can be a dangerous business. I have to chuckle at those that say a click or two in either direction will do no harm. There is no such thing as a click or two, tighter than spec. Maybe up until, but not after you mat it. Look at the adjustment procedure.

RACE ON!!!

 

Did your transmission guy use your original trans? Corvettes have their own governor. My 85 had the trans replaced before I got it and they put a rebuilt one in, my shifts were almost 6,000 rpm at WOT. I put a Corvette specific governor in it and now it shifts where it should. Follow PeteK and CFI-EFI's advice and only adjust the tv cable to factory specs or you could be giving the tranny man more $$$.

 

I use a gauge when ever I install a rebuilt OD trany because the TV cable can destroy a trany in short order if the pressures are not correct. Here is a good explanation on TV cables and what they do. http://www.tvmadeez.com/article/index.php

 

Good advise. This is true anytime a new or used trans is installed. It is especially true if installing a 700r4 in a carburated car.

 

For maximum line pressure at WOT, the TV cable should be set on the tight side (not over tight) just no slack in the TV cable setting at WOT. If the tranmission shifts late at WOT, then backing off is going to reduce the line pressure and do little if any in change of the WOT rpm shifts, and probably do damage to the transmission. You solve this with a change in the weights & and a little from the springs.

 

Thanks guys I see a visit to the tranny guy in my future if he won't help Iam bringing it somewhere that will and pray for the best. So sense owning one of this things if your unhappy with it.

Jeff

 

good info