Please read this, I need to know what happened. Ok, here's the deal. I had a stock 700 trans in my car a long time ago, and it went out on me. I had a good friend of mine that has worked in trans shops for 17 years take it apart for me to see if he could rebuild it. What he found when he took it apart was the reverse drum where it forks together was pushed outwards and was scoring the inside of the trans case. He told me there was no salvaging it, and that in his 17 years had never seen anything like it nor could he say what caused it. I then purchased another used 700 in good cond't and had the same guy put a B&M shift kit into it. It then lasted me another 3 weeks and went out. I then sold it to another guy who rebuilds trans' on the side, and he just called me today, saying that the reverse drum had forked out and started to score the inside of the trans case!! He also had no idea what could have caused it and couldn't believe what he was seeing and wanted to know if my trans had been shifting overly hard (which it wasn't, it was nice and firm) or been making any noise (none). I could not believe my ears when he told me this, that I had done this to two transmissions in a row which neither guy had seen before in his life, nor could explain the cause. So I wanted to ask all you trans experts on here if any of you have ever heard of something like this happening, and what could have caused it. I'm extremely curious to know what happened, and I want expert input so that I know that these trannie's blowing up wasn't my fault in hooking something up wrong. Thanks for reading all this and any replys.

 

The input sprag is sliding, when it should be holding. When this happens the reverse input drum can go up to 3 times engine rpm's, this allows the drum and or sunshell to expand and sometimes enough to start tearing uo the case. Both parts have to be replaced, and the input sprag assembly needs to be the latest from Borg Warner and the inner race needs to be in near perfect condition (the surface needs to be "extremely" smooth) and the outer race in good condition but roughened up with 80 grit sandpaper in the direction of rotation, this will stop this from happening. The overrun clutches should be Borg Warner also. While you are this far into it repalce the input to output shaft seal with the "viton", this will guarantee lube to the rear planet, and put in the Borg Warner Hi-Energy 3-4 clutches for longer life.

 

Like Dana said, its centrifical force bending those tangs out. I saw some of those at the GM Training center, but never saw one in the "field".

You must be sitting at red lights and revving the engine like a rlcer... J/K

Jesus, you can't even say rlcer w/o it being being censored. What is this world coming too?

 

Ok, that makes good sense then. The sprag slides and allows the drum to rotate at around 1500 rpm's or so, I can see how that would make it fork out like that then. But the thing I still don't get is what would cause this to happen to 2 transmissions in a row? What causes the input sprag to start sliding when it should be holding? Dosn't sound like it happens to much, and just don't get how it happended to me twice in a row. And plus, I really wasn't breating on these trannie's all THAT hard, or keeping them at a high rpm very long, so I don't see how they could fork out so far so quick. I guess i'm just mainly confused about why the sprag would start doing that to allow the drum to expand, since it happend twice. Why's that happen??? Thanks in advance guys, I appreciate your knowledge.

 

Bliss,

I'm busting up over the ***** comment...... Makes me want to go out and order a combination plate........

 

From what I've read there is a heavy duty sprag (28 element?) to cure this problem. I guess the stock ones don't apply enough force to prevent slipping. Or the inner race is scored up on the rebuilt trans. My 2nd 700r4 did that, Now it just breaks the reaction carrier shaft and takes out the rear planetary. I'm saving up for the h/d stuff 5 pinion planets, hardened sun shell, intput shaft etc. Then I can start breaking driveshafts. Weee!

 

The later 700's came w/ 28. The newer Borg Warner is 29 element, the same used in later 4L60-E.

 

But the main thing I want to konw is what would cause the input sprag to slip when it should be holding?? I understand now that when that happens it will cause the drum to expand, but what causes that to happen?? I'm still really confused about that part. Any answers?? Thx.

 

Probuilt or anyone else, do you know why the input sprag would slide when it should be holding?? I'm really trying to figure this one out and I can't. Thx.

 

When the sprag itself has to much wear on it, or a sudden increase in torque or horsepower, possibly the wrong type of fluid (not likely), bad parts from the start (case hardening to shallow on inner race), etc.