700R4 TV Cable Adjustment Lies, Bull, and What's the Truth?

[Erik the Awful]

I just got my newly rebuilt transmission in WCJr, and I'm struggling with the TV cable adjustment.

If you google it, you'll find plenty of f'n morons on YouTube and elsewhere saying that all you need to do is adjust the TV cable to where your transmission 1-2 shifts between 10-15 mph, and 2-3 shifts between 20-25 mph. Bull$#!+. That's how I burned up my last transmission.

There are guys who tell you to tighten the cable up and then floor it and it will set itself. Apparently this works fine if you have a factory TBI, a factory TV cable, and a not-so-minor splash of luck. I'm running a Holley Sniper, and so far haven't found any luck. I did measure as carefully as I could and set up my bracketry to mimic the factory TBI bracketry. The arm radius appears very close and the throttle and TV cable distances are set the same as the factory cables. The Sniper does have Holley's throttle arm corrector on it, but not the TV cable corrector that Sonnax sells.

Then there are the guys who tell you that you need to set it with a pressure gauge, but they don't give you a clue which port to use, and the pressure specs are wildly different depending on who you talk to.

I plugged my gauge into the line pressure port on the driver side of the transmission and played with the cable until I got 75-85 psi on the gauge. Then I dropped the gauge and broke it. One quick trip to HF and the new gauge reads much more consistently than the '90s era gauge I was using. Once I got the new gauge installed I took it for a test drive with the gauge hooked up. It maxed out at 90 psi.

Then I tried the with the cable tightened all the way up and floored to self-adjust. I'm getting a very consistent 120 psi max. I can't get it any tighter without it resetting at full throttle. It seems to be shifting fine, but I know that's really temporary if the cable's wrong.

Is my transmission pump weak? Am I checking the wrong port?

If the transmission comes out again, the NV3500 is going in its place.

 

[NickTransmissions]

I just got my newly rebuilt transmission in WCJr, and I'm struggling with the TV cable adjustment.

If you google it, you'll find plenty of f'n morons on YouTube and elsewhere saying that all you need to do is adjust the TV cable to where your transmission 1-2 shifts between 10-15 mph, and 2-3 shifts between 20-25 mph. Bull$#!+. That's how I burned up my last transmission.

There are guys who tell you to tighten the cable up and then floor it and it will set itself. Apparently this works fine if you have a factory TBI, a factory TV cable, and a not-so-minor splash of luck. I'm running a Holley Sniper, and so far haven't found any luck. I did measure as carefully as I could and set up my bracketry to mimic the factory TBI bracketry. The arm radius appears very close and the throttle and TV cable distances are set the same as the factory cables. The Sniper does have Holley's throttle arm corrector on it, but not the TV cable corrector that Sonnax sells.

Then there are the guys who tell you that you need to set it with a pressure gauge, but they don't give you a clue which port to use, and the pressure specs are wildly different depending on who you talk to.

I plugged my gauge into the line pressure port on the driver side of the transmission and played with the cable until I got 75-85 psi on the gauge. Then I dropped the gauge and broke it. One quick trip to HF and the new gauge reads much more consistently than the '90s era gauge I was using. Once I got the new gauge installed I took it for a test drive with the gauge hooked up. It maxed out at 90 psi.

Then I tried the with the cable tightened all the way up and floored to self-adjust. I'm getting a very consistent 120 psi max. I can't get it any tighter without it resetting at full throttle. It seems to be shifting fine, but I know that's really temporary if the cable's wrong.

Is my transmission pump weak? Am I checking the wrong port?

If the transmission comes out again, the NV3500 is going in its place.

Ill look at this more closely later today and respond if you haven't resolved by then; occupied atm.

 

[Sean Buick 76]

You need to check your line pressures otherwise you are pissing in the wind.

 

[Erik the Awful]

You need to check your line pressures otherwise you are pissing in the wind.

I plugged my gauge into the line pressure port on the driver side of the transmission and played with the cable until I got 75-85 psi on the gauge.

 

[Sean Buick 76]

You need to document your line pressure in neutral and in each gear. It only takes about 10 minutes of driving to completely ruin a 700R4 due to line pressure. Have it towed to a trans shop before it needs a $2000 rebuild.

 

[NickTransmissions]

@Erik the Awful - Harbor Freight gauges are hit and miss but assuming it's not defective, 90 or even 125 PSI max line rise tells me the TV plunger and sleeve in the valve body may be worn. Very common reason for seeing stable, acceptable line pressures at idle yet less then optimal line rise at stall / under heavy acceleration when driving.

Sonnax makes an improved plunger and sleeve kit to address this concern.

Throttle Valve Plunger Valve Kit - 77966-94K

Poor line rise or no detent downshifts can be common complaints in vehicles with a THM 700-R4 transmission. The steel throttle valve plunger continuously rec

www.sonnax.com

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What are your pressures in reverse?

Additionally, your geometry has to be perfect, not just 'close'. I've seen plenty of set ups with the wrong bracket that was able to get the geometry close but not where it really needed to be and line pressure rise was inconsistent/inadequate...These are on 700R4s that I built and went to help customers trouble shoot because they could not get adequate line rise when running the pressure test at stall.

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Did you rebuild the transmission?

If so, what were the clearances in the pump? What boost valve was used?

Line pressure chart for those following the discussion.

You must be registered for see images attach

 

[Erik the Awful]

The transmission got a $250 "rebuild" by a friend's cousin. I absolutely knew it was going to be a crapshoot, but I was willing to take a chance on it. If the plunger and sleeve are worn but acceptable, I have no problem with that.

I just went out and fired it up again to recheck the reverse pressure - 120psi @ 1000 rpm.

Just as a historical note, I'd dropped $700 previously rebuilding the original transmission myself, and it drove okay for about two weeks before burning up. This is a last chance for 700R4s in my truck. As stated above, if the $250 rebuild doesn't work it's getting an NV3500.

 

[thinger2]

@Erik the Awful - Harbor Freight gauges are hit and miss but assuming it's not defective, 90 or even 125 PSI max line rise tells me the TV plunger and sleeve in the valve body may be worn. Very common reason for seeing stable, acceptable line pressures at idle yet less then optimal line rise at stall / under heavy acceleration when driving.

Sonnax makes an improved plunger and sleeve kit to address this concern.

Throttle Valve Plunger Valve Kit - 77966-94K

Poor line rise or no detent downshifts can be common complaints in vehicles with a THM 700-R4 transmission. The steel throttle valve plunger continuously rec

www.sonnax.com

------------
What are your pressures in reverse?

Additionally, your geometry has to be perfect, not just 'close'. I've seen plenty of set ups with the wrong bracket that was able to get the geometry close but not where it really needed to be and line pressure rise was inconsistent/inadequate...These are on 700R4s that I built and went to help customers trouble shoot because they could not get adequate line rise when running the pressure test at stall.

------------
Did you rebuild the transmission?

If so, what were the clearances in the pump? What boost valve was used?

Line pressure chart for those following the discussion.

You must be registered for see images attach

Agreed. Linkage geometry has to be "perfect"
Cable orientation to throw of the cable as it relates to throttle open has to be exactly right per the factory GM diagrams.
There is no close enough on a 700r4
Ive smoked at least 4 of them
With an aftermarket setup you cant trust any part of that.
There is a very specific geometry between the throttle linkage and the TV cable and you cant go outside of that geometry no matter what intake or carb setup you have.
That geometry between the throttle plate opening and the cable that goes into the transmission always has to be exactly right for a 700r4 to not burn up.
An aftermarket carb or a carb spacer or any change in that geometry will fry a 700r4 really fast.
It isnt about the linkage at the intake.
It is all about how that TV cable moves inside of the transmission.
If you have the wrong cable or an aftermarket carb or a riser or anything that makes that cable throw different than factory.
You will cook your 700r4
That TV cable and its relationship to the throttle linkage is attached to the the transmission and it uses that cable to set shift points and line pressure.
Things that really need to happen in a predictable way.
That cable controls where the transmission fluid goes and if it applies pressure and shift points Etc...
You really need to get the TV cable set up perfect
.

 

[Erik the Awful]

With the engine at 1000 rpm in park I pulled the TV cable taut and it still only went up to 120 psi. From what I'm understanding, manually pulling the TV cable should get me to that 166-203 psi range. Is that a clear sign the transmission is a fail?

If not, does anybody have experience with Sonnax's $75 bracket and corrector kits? As stated above, I duplicated the geometry as best I could.

More Information for SONNAX AS404K

More Information for SONNAX AS601

Performabuilt Transmissions has a pretty good video explaining that most of the info out there is bunkum and he talks about taking the pan off and very exactly adjusting the TV cable so that it rests right up against the plunger at idle and fully actuates it at WOT. This may be my next step, but it'll be a couple weeks before I can tackle this again.

xc_hide_links_from_guests_guests_error_hide_media

@NickTransmissions - I did check to see if you had a TV cable video first.

 

[NickTransmissions]

With the engine at 1000 rpm in park I pulled the TV cable taut and it still only went up to 120 psi. From what I'm understanding, manually pulling the TV cable should get me to that 166-203 psi range. Is that a clear sign the transmission is a fail?

If not, does anybody have experience with Sonnax's $75 bracket and corrector kits? As stated above, I duplicated the geometry as best I could.

More Information for SONNAX AS404K

More Information for SONNAX AS601

Performabuilt Transmissions has a pretty good video explaining that most of the info out there is bunkum and he talks about taking the pan off and very exactly adjusting the TV cable so that it rests right up against the plunger at idle and fully actuates it at WOT. This may be my next step, but it'll be a couple weeks before I can tackle this again.

xc_hide_links_from_guests_guests_error_hide_media

@NickTransmissions - I did check to see if you had a TV cable video first.

Yep, that's a good vid...Typically, the plunger will be pre-loaded when the TV cable has the appropriate amount of tension upon adjustment but def worth checking. If it does, I'd just replace the factory plunger and sleeve with the above mentioned Sonnax part and then retest...It also comes with a TV boost spring which will also help...If you do and it's still not responding as it should, I'd suspect either the TV boost valve in the VB is worn or the pump boost and/or PR valve are worn (they can be replaced at the same time as the plunger/sleeve, trans removal not required) or pump rotor-deck clearance is excessive (would require trans removal, pump removal and teardown and pump re-machine or replacement with a re-man pump to correct).