My 700 has done it twice now, once to the point of me overheating my 205 from the fluid thinning out so much , and draining about a 3 quarts of "mixed" fluid out of the FILL plug of the 205 on the way to TDS in March.
I have the TH700 with the GMadapter and a 205...
My questions:
What causes this? Is it just a seal that dried out from sitting for 8 months while I did my last motor?
Can I just pull the t-case/adapter and change the seal in the back of the tranny?
Is the fluid actually being "pumped" into the case or just leaking - anyone have a good flow chart for the 700?
also, possibly not related but maybe
The four bolts that bolt the adapter to the Tranny keep loosening up (we're talking about 200 miles or so)... What would cause this?
I know one time (the first time I became aware of this) they were loos enough to make a vibration, I'm guessing this could have destroyed the seal as well??
Any input would be greatly appreciated... I'm down to 4 weeks till Rubicon and have to get this fingered out...
Pete, I'm not 100% positive, but the seal between the TH700
and the t-case is probably an o-ring. Sounds to me like like it's
toast. As far as the bolts loosening up on you, buy some new
bolts with the drilled heads and lock wire them. That should at
least keep them from backing out.
Thanks Gary...
I think the oring is between the adapter/trans and keeps the fluid from leaking externally...
I think there would have to be some kind of seal around one or the shafts on the rear of the trans or front of the adapter or rear of the adapter or front of the x-case to stop "fluid mixing" this is what I need to know and what is required in fixing this seal...
This place has some excellent info on the 700 and many other trannies. SOunds like a dried up seal, like you said. I know from personal experience those trannies don't like to sit for very long without use.
I had the same problem a while back. Turned out the spline adapter from the transmission output to the transfercase input was loose from wear. There is a o-ring inside the adapter sleeve to seal the shafts up. If there is much play between the adapters and shafts, it won't seal. I tried a little RTV, but it just leaked again and I had to pull the case again . I ended up replacing the adapter sleeve and t-case input shaft to fix mine.
A 205 will work fine on ATF, in fact that is what GM specifies in the later years that 205s were used behind automatics. They changed the spec from gear oil because of the problem you are having now, it is VERY common.
Thanks for the inoput so far guys! It sounds like it's the o-ring around the adapter shaft that took a crap....
I'm open for more suggestions if anyone has them...Thanks again
rear seal on the tranny. 700's are famous for it. S10's have that problem frequently. when you check the fluid level in the T-case, and get 6 quarts of fluid in your lap, you know you have a rear tranny seal out. I've never changed one. I just drain off the excess and keep an eye on the tranny. But I can do that since my tranny and t-case use the same fluid. and I also agree with using the safety wire on the adapter bolts.
I had this problem once with a 700R4 and NP 203 combo. The o-ring seal is for external leak protection. There is no seal at the rear of the 700R4 transmission so if your input seal on the transfercase is bad oil can be "pumped" in by the turning motion of the shaft spinning in the bad seal. The transmission can get quite hot since it is low on fluid and this can make the transfercase radiate a lot of heat--plus its not designed to run on ATF. The 700R4 bolts are metric but are similar to the U.S. bolt so if you mix these up your bolts will loosen. Turbo 350's and 400's are gennerally US bolts. Two of the bolts in a 700R4 are blind holes the other two will accept nuts on the back side of the case if you buy longer bolts so this helps if you have a driveline vibration problem that can loosen the bolts.
Jason
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