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700r4 shifting problems- Please help.

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roydavenport

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I have a 91 Suburban with a 6.2 diesel and 700r4 tranny. The last 2 or 3 times I've driven it I noticed it starting to shift a bit later and harsher than usual. Now today on my way back home from my sons class, it didn't want to shift into second or third. When I took off from a light the engine just revved right up in first intil it wouldn't go any faster and wouldn't shift into second until I let up. Got on the gas again and it did the same thing again and wouldn't shift to 3rd until I let up. Got back on the gas and continued on and it shifted on up through the gears eventually getting to overdrive, but taking longer than normal for each shift. The problem seems to lessen to where it's hardly noticeable once the tranny heats up. It acts up the worst when I first get rolling and the tranny is still cold. It seems to have plenty of fluid. Any ideas? Thanks in advance for the help.
 
Make sure the TV cable is connected and working and if needed remove the governor and inspect it for damage.
 
X2

Thinking there is a problem with the TV cable. Maybe binding up and not working properly.
 
I admit that automatic transmissions are one of the things on trucks that I know next to nothing about how they work. I've had others also suggest the TV cable. My thoughts are that with a cable either it works or it don't. I'm not saying that anybody is wrong, but could someone explain to me why if it's the TV cable that once the transmission warmed up that it seems to shift ok. I'm trying to understand why transmission temp factor seems to be making a difference. Thanks for the replies.
 
well, the automatic transmission uses fluid pressure to engage or disengage different parts. When an auto trans is cold, the pressures are higher, which would effect shifting, once warmed up, pressure drops a little and creates softer shifts. The TV (throttle valve) cable is the only way the transmission knows what the engine is doing...it adjusts line pressure accordingly to how much throttle (input) your giving it...

If the TV cable becomes stretched, it will not be accurate anymore and the shifting will change.
 
Yep, as a transmission wears, the seals get old and hard. Pretty much the opposite of us men darn it....

But that means as the fluid warms up and thins out all the pressures drop. That particular transmission is, in my opinion way too dependent on the TV cable for control. Lots of other ones just use it for kickdown, or shift points.
That one has very low pressure at idle, but it jumps up rapidly when the cable moves.

If the cable comes loose, stretches, or gets out of adjustment in any way, it will burn up the transmission real quick because there is not enough pressure to engage the clutches and brake bands.

Just like driving down the road with the clutch partially pushed in on a manual.

The method of adjustment it to retract the adjustment all the way back, and then push the throttle to the limit.
The correct adjustment is when the cable is stretched all the way out just at wide open throttle.

However, if someone changes the throttle linkage, such as putting on a different carb, or converting it from TBI to carb or the other way, then the cable might be all the way out at WOT and still be wrong.

Not only is it important at WOT, but the rate and distance that it moves is important also.

Either way, it can cause big problems and should be checked anytime you notice anything change with the tranny.
 
Thanks for the explanations. It makes way more sense now. I was thinking that the cable served only as a "kick-down" linkage. I didn't realize it was so important to the shift patterns on this transmission. I'll try and adjust it asap and see what happens. Thanks again.
 
Any resolution to this?

Mine started the same exact symptoms yesterday. Very long, delayed shifts when cold (of course it's been cold outside this week also), then as the tranny comes up to operating temp it seems to return close to if not all the way to normal.

I have not changed anything with my throttle valve cable, nor can I see anything blatently obvious during a quick slide under the truck and look under the hood.

I plan on dropping the pan tomorrow and checking everything out, changing up the filter and fluid.

Does anyone have an easy to follow procedure to re setting the TV cable? Or should I get a new one as this one may be "stretched" or otherwise compromised?

Any help would be appreciated, didn't plan on rebuilding a transmission at Christmas. That would really throw some suck into the holiday.
 
Try changing the fluid and filter

I pm'd Greg Ducato, another member who came up on every search I did 700R4 related. He suggested the filter was clogged and to change it.

I did this morning, was extremely happy to find no debris in the pan:woot:, put in a Wix filter and re filled with 5 qts of Royal Purple Max ATF as well as a pint of Seafoam TransTune.

Drove it. At first it acted the same as before, longer shifts, a bit harsh when it did, and most times in 1-2 or 2-3 I'd have to let off the gas a touch to get it to shift up. After a short distance, 3-5 miles, it cleared up, almost instantly. Drove it at varying speeds and it shifts smoother now than any time in the last 2 yrs I've owned it.

Plan is to let it cool completely over night tonight and check it out in the morning. I'm thinking that did the trick.

One thing I noticed while changing my filter. The o-ring on the old filter neck was stuck up in the oriface. It was a pain in the arse to get out. Finally got it.

Thanks to this site and members like Greg for the help.:bow:

Perhaps your issue will be resolved similarly. Good luck.
 
I recently read a service /overhaul manual for 700r4's I came across at a flea market,one of the best ones I have seen yet--has step by step rebuilding procedures,pictures,and shows how to modify the pump passages for longer life,etc...

One "tip" in the book shows how some aftermarket pan gaskets block off a drilled passage between the pan bolt holes,and it says it can lead to shifting troubles and worse problems,so they reccoment making sure whatever gasket you use doesn't block off that passage!..
 
That's interesting because I changed the fluid and filter with new gasket about 1000-1500 miles before it started acting up. I don't remember seeing any kind of hole that could have gotten blocked off by the gasket though, but it's worth a check. I did try adjusting the cable, but it still isn't shifting right.
 
It sounds like you've been having a valve stick from some debris somewhere - probably just clutch material from normal wear. The 700 has one valve that is especially prone to sticking. In the TV assembly, the innermost piece is floating. That is, there are no spring on it. It is pushed "in" by the rest of the valvetrain as you open the throttle. Then it is returned only by fluid pressure. When it's stuck the shift points can be as high as WOT. The fact that yours was affected by the throttle position tells me that whatever was sticking was still able to travel partway.

New ATF is an incredible solvent. After changing it you may run through some other problems as other old junk starts moving around.
 
Blue85 said:
It sounds like you've been having a valve stick from some debris somewhere - probably just clutch material from normal wear. The 700 has one valve that is especially prone to sticking. In the TV assembly, the innermost piece is floating. That is, there are no spring on it. It is pushed "in" by the rest of the valvetrain as you open the throttle. Then it is returned only by fluid pressure. When it's stuck the shift points can be as high as WOT. The fact that yours was affected by the throttle position tells me that whatever was sticking was still able to travel partway.

New ATF is an incredible solvent. After changing it you may run through some other problems as other old junk starts moving around.
Click to expand...

I would have to agree. I'm dealing with a simular issue with my 89K5 / 96 vortec swap. It seem's that the Tv assembly bore/plunger in the Valve body is worn causing it to stick. Changing the fluid on a used trans (if it has ever been changed) when we start to notice a problem is like playing russian roulette. It will show signs that it shifting better.... Than surprise you only can go in reverse.
That's only in my experience with Transmissions not saying for anyone else.

roydavenport:
Here is a link http://www.tvmadeez.com/ that I used for setting my TV cable.
Hope it helps.
 
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