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700R4 shifting problem

S

ShamrockRacing

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hey all, i've got an 87 k5 that i recently swapped motors on. (blown up 350 with not blown up '69 4 bolt but nothing too fancy). the trans (700r4) shifts fine 1-2, but when it wants to shift into third, it goes into neutral and starts revving instead. it does this in 2wd or 4hi, i havent tried in 4lo but expect it wouldn't matter. i can drive around town holding it in 2nd, but obviously i cant get on the freeway. the tranny fluid level is fine. when i was swapping the motor i broke the end off the kickdown cable (where it attaches to the throttle linkage), but i put on a new end with a short extension so that is very close to the length it was, but maybe not exactly right. i left the tranny in the car so the sift linkage didn't get disturbed. any ideas? Help!
 
Get a new tv cable for the trans and then make sure it is adjusted properly. 700R4's are very tempermental with tv cable adjustment. I wouldn't drive it too much the way it is until you get that fixed, apparently an improperly adjusted tv cable can burn up the tranny pretty quick.
 
I second gauder's comment, and can tell you from experience he's right. It's a common misconception that the cable you mentioned is a "kickdown" cable. It's not -- it's a TV (throttle valve) cable, and it's positioning controls certain pressures within your transmission. Drive around with it unhooked, or even improperly positioned, and you'll burn the transmission up very quickly.

I did almost the same thing you did. Swapped in a new motor and didn't know to even hook up the TV cable. Had the same problem you did slipping into neutral, and thought it must've been because of the massive horsepower the new motor was putting out. (You can all laugh now) Even when someone pointed me in the right direction, I found that it's an unholy pain to get the thing correctly adjusted. Theres a slider connection with a pushbutton release that should attach to your carb linkage. By pushing the button, you get about 30 or so different adjustments, and boy is it finicky. In the end, I burned up 2nd gear because I never got the cable right.

There's a good walkthrough of adjusting the cable here: http://www.powerdemon.com/PowertrainPointersFEB03.html

If you have problems, IMHO it's worth paying the guy at the local transmission shop to set it for you. They can put gauges on the transmission and make sure that everything's ok. Doing it yourself is fine, but when you look at $1800 for a 700R4 rebuild....

Hope this helps.
 
A misadjusted TV cable will cause a sloppy 1-2 shift ( 1-2 shift will slip) so if your 1-2 shift is good then most likely the throttle valve cable is adjusted in the ball park, I have never seen a TV cable cause a missing gear. Check your fluid and if it is burnt then you have roached your 3rd clutch pack, you will need to tear is down to make sure but I'll bet from all the 700r4's and 4L60-E's I have rebuilt your input housing (input shaft and bell) is leaking somewhere around the 3rd clutch piston (with the input housing removed and fliped over and disassembled it will be on the bottom). A new input housing and a overhaul and you shoulb be fine. And remember always installed a new TV cable and a governor when you rebuild. Do not buy those "universal" one form Napa, buy the GM factory one only 12 bucks. Good luck.

One more thing, in order to have 4th gear, third clutch is holding and the 2-4 band is applied, so if you are missing 3rd, you got no 4th. Only first and second gear.
 
It sounds to me like the 3-4 clutch packs are shot and just slipping. My brother had that happen to him when he put a V-6 transmission behind his 305. He ended up eating the clutch faces off shift 1-2 was fine when it hit 3rd it would just rev up. My uncle who is an ASE Certified GM Mechanic said it is called "Flaring" and told us the problem. We took it apart and the clutch pac looked like nothing but steels there was no friction material on anything.

Ira
 
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