700R4 trans

[GrimmJeeper]

ive got a 86 astro van with a 700R4 in it. yesterday it clunked really loud while sitting at a stoplight and killed the motor. i started it right back up and it wouldnt move. i can move it through the gears and its like im not doing anything, no RPM change on the motor, nothing at all happens. i dropped the pan today to see if something had come loose inside, but it looks fine, the fluid is clean and not burnt, the shift selector is moving the piston through the valve body just fine.


anyone have experience with these transmissions? im just wondering what could have caused it to act like this. i'd like to avoid taking it to a trans shop without figuring out what is wrong with it first. i was thinking maybe the pump went out on it or maybe a problem with the coverter.

help!
thanks
-G

 

[Oatmeal]

Not sure about GM transmissions but, I stripped the input shaft splines in the torque converter of the C4 auto I used to have in my early Bronco and it acted just like that.....other than that, the trans was fine! Maybe it's something as simple as that :dunno:......I used to have a really heavy foot back then--------Hans

 

[Gerr]

sounds like a bad torque converter to me, had 2 in chevys go clunk and then nothing

 

[RobertF]

If you're really feeling nothing while cycling the shifter, no preasure applying any clutch pack or band, pull a tranny cooler line off, put a baggy over each end, and run the engine for 3-5 seconds.
If there's not a baggy full of trans fluid on one end or the other, the convertor's not even turning, like the bolts fell out of the flex plate, and there's no preasure coming out of the front pump.

 

[5-90]

86? I can tell you one thing - when you replace it, get one made after 1990.

The earlier THM700R4s were barely fit for scrap metal. I had a buddy with a 1987 S10 Blazer who went through five rebuilts in a year (he didn't do them himself, and only paid for the first one,) before he told me about it, and I told him to get a later box. That solved the problem.

Various modes of failure - there wasn't anything that could really be tracked down and fixed.

Up to about 1990, the 700R4 was, simply, crap. I don't know why, I don't know what they were doing wrong, but it was fixed after that, and worked just fine until it was "updated" (to the 4L-something or other-E.)

 

[swbooking]

Mike, if you do end up taking it to the shop, my Uncles place is in Hawthorne on Rosecrans its called California Transmission. If you shoot me a PM before you take it in, ill let him know your comming. Might be able to work you a deal or something.

 

[jeeperjohn]

I had the center of the flexplate tear out on a car before. It clunked then engine died then engine would run but no movement.

 

[GrimmJeeper]

damn. Allen wish i would have seen your post sooner. my boss had the van towed to a trans shop this morning at 8am. they called us at 3 and said the front pump is bad, converter is fine, and they are charging him 1000$ to replace the pump and put it back in.

oh well. next time i need transmission work i'll shoot you a message.

thanks for the info guys.

:wave1:

-G

 

[swbooking]

damn dude... oh well. Yeah for sure let me know.