Trans fluid blew out overflow (vent tube) on top of trans?

[troubles789]

I was driving in the mountains of TN and VA. Doing anywhere from 70-80 mph On the steep inclines straight up. There was alot of kickdowns. Was not using OD at the time do to the steep roads. I noticed a bunch of smoke coming from underneath, out of the back on one of the kickdown climbs, trans fluid even went on the rear glass and tailgate areas. Then it stopped less then a 1/8 mile. Stopped and checked everything out. Trans fluid was dripping from under the 1993 jimmy 4.3w auto. Fluid levels all checked out and everything worked fine, so I cont on my trip. It never did it again.
So what would cause this trans fluid blow out of the vent tube of the trans? Anyone else having this happen. Has only done it twice since owning this GMC. Other time was 8 years ago doing 85mph passing on a mountain. Ideas?

[BlazerLT]

Transmission was overheating.

Time for a fluid change with a new filter and have your transmission cooler flushed out.

[Jeremy Fitch]

I have also seen this happen when the transmission was overfilled.

[stolanother]

As I have been reading through these forums I find this to be a common problem with blazers. The ATSG transmission service manual for 4L60E transmisssions states if fluid comes out vent tube the problem is the oil pump (chamfer in pump body rotor pocket to large). Or fluid level is to high. Changing the filter will not help, trust me I already did that to mine. I ordered a rebuilt pump on ebay for $195.00 and I am just waiting to install it.

[troubles789]

Originally Posted by stolanother

As I have been reading through these forums I find this to be a common problem with blazers. The ATSG transmission service manual for 4L60E transmisssions states if fluid comes out vent tube the problem is the oil pump (chamfer in pump body rotor pocket to large). Or fluid level is to high. Changing the filter will not help, trust me I already did that to mine. I ordered a rebuilt pump on ebay for $195.00 and I am just waiting to install it.

So what year is your blazer? 93 jimmy s-15 here. Does mine have that trans you listed? I thought it was in the bigger brothers.
So did your trans fluid blow out all the time? Mine only did this twice, 8 years apart, driving hard in the mountains.

[BlazerLT]

fluid overheating will also cause fluid to come out the vent.

[stolanother]

My blazer is a 1995. My fluid was blowing out all the time, but a year prior it was just leaking every once in a while. It does get worse. Anyways, I replaced my transmission pump with the rebuilt one that I got off ebay, Drove the vehicle 6hrs at 70 mph down the interstate and have no more leaks out the vent tube. It was not a fun job to do because of cramped spaces, but I did it. 2 day job for me. I hope this helps you guys that have the same problem.