Thread: Yet another 700R4 tranny question...

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Hi Guys, got a question for you. I have a 1990 Chevy Suburban 1/2-ton 4x4, w/ a fuel-injected 350. There are 220,000 highway miles on the motor. I have been having some real issues with the 700R4 tranny, and need some feedback.

When we are on the road the motor won't kick down, and it doesn't matter what speed we are going at. It used to be that the motor would drop down at 40-45 on its own, but now it will only do it very, very occasionally, and then only when I let of the gas for a second. If I don't try to get it to kick down that way it will happily roar away at 50-60-70 MPH.

No other shifting issues that I am aware off, the tranny fluid level and color seems fine, and the tranny has never been rebuilt. BTW, while a slug traveling up hill is faster than this Suburban, it doesn't seem to use oil and doesn't smoke. If I can figure out an easy solution to the tranny problem I might be able to get another 50k out of this unrusted, undamaged vehicle. I consider this a hot rod topic because I use this overgrown station-wagon to fetch parts for my 71 Lincoln Coupe Lowrider !

Any suggestions from the wise ones here on the board? Thank you in advance for any help.

Michael

Originally Posted by 71LincolnCoupe

Any suggestions from the wise ones here on the board?

Hey Michael, I wouldn't consider myself "wise" so much as I would "a wise guy". Anyways, your problem is an easy fix. Simply adjust the TV cable. You will have to find the tab within a housing just behind the bracket that holds this cable. Push it in, then move the weiner backwards towards the firewall. The weiner is the part that holds the wire cable and exits forward through the bracket.

If you disconnect the cable from the throttle body linkage, then with the engine off, open the throttle wide open, then pull the tv cable forward to see if matches the hookup knob. If it is short, that is better than if it is long.

I just did this very same thing for another guy two days ago. Now he loves his truck again.

Boy, that DOES sound like an easy fix! Anyone else here concur with TyphoonZR's suggestion? BTW, what does the "TV" term mean? Throttle Vacuum? I knew I would get some good advice here.

Michael

Throttle Valve = T.V. Basically a valve in the tranny is activated via throttle movement. The more throttle you give your vehicle, the more fluid pressure is applied to the frictions and bands. Also the more throttle you give your vehicle the later the shifts occur. Consequently, in your case, the valve is not being opened enough therefore the shifts occur as if you are driving with a light throotle when in effect you are at full throttle.

Yeah, you have summed up exactly what symptoms seem to be. I took the truck to a local tranny shop a while back to see if it the problem was something small and easily fixed, and the owner recommended a complete overhaul.

I shied away from that because while there are quite a few miles on this rig, there haven't been any other tranny issues that I recalled. I am no mechanic(obviously !), but it seemed that if the transmission was actually that bad, we would be seeing other problems as well.

Since that diagnosis from the shop we have put a couple thousand more miles on the Suburban, sometimes upto 70 miles one way at one time, and this is the only tranny problem that crops up. Sounds like that place was trying to reel me in with a hook in my mouth.

Thanks for the good advice TyphoonZR, the wife and I appreciate your help in saving us some cash. Regards...

Originally Posted by 71LincolnCoupe

I took the truck to a local tranny shop a while back to see if it the problem was something small and easily fixed, and the owner recommended a complete overhaul. ...

hahaha, think about it, there is no benefit to him for adjusting your tv cable. He probably wouldn't have charged for that.

Originally Posted by 71LincolnCoupe

Thanks for the good advice TyphoonZR, the wife and I appreciate your help in saving us some cash. Regards...

HEY, it's not done yet. You have to let us know if it worked! I may still be wrong, remember, even a broken clock is right twice everyday!

Sorry for the time it took to update. Turns out that the problem was caused by a bad fan clutch. We replaced it with another, and the rig shifts again like it is supposed to. Thanks again for the responses.