4L60E puking fluid out the vent tube


Well-Known Member
May 28, 2001
What would cause a 4l60E to start puking tranny fluid out the vent tube after about 20 miles. Fluid drips onto the exhaust and turns into a mosquito fogger.

Tranny was reverse flushed in Feb. and just got the AC fixed last week after 2 months with bad low pressure switch.

Would the hi temperatures cause this, ist been 90+ the last 2 days? Should I start with a filter and fluid change and see what happens? Fluid level was low yesterday when I got home?

Any suggestions?


P.S. Doesn't seem to operate any differently
Make sure that the TCC is functional. If it's not working, that could drive up temperatures.
Overfull? That would do it. Ck hot.

The fluid was low yesterday after it was puking the fluid out the vent tube. Added a quart this morning and got it into the cold range, I stopped while it was leaking the fluid today and it was was in the middle of the hot range.

I used the same technique as I used to troubleshoot my GN's TCC and it appears as if the TCC is working.

On #turbobuick chat, Kendall said that possibly the Pump drain could be plugged, would that be possible?


P.S. This is on a 95 s-10 blazer, the vent tube parallels the tranny dipstick tube and ends about 2 inches below the top of the Dipstick tube.
Possible? Anything is possible but I dont know what it is he is referring. Sounds like heat generated and/or pump cavity wear. I wonder what line pressure is? If slide in pump stuck in high volume postion it could pump some out the bleed orifice into vent cavity. Thes are tough problems to find because you have no "damage" other than fluid which once you pull is everywhere anyway. Drain? I have no idea unless he is referring to pump seal return and 4l60e's are not known to have that problem. early 700's did but not this one. Man, tough one. Ck and recheck cooler flow.

Check for codes and expect to find code 1870. This means that there is a trans component slip. Upon further inspection you would find that the TCC Regulator valve bore is worn enough that the valve is sloppy in the bore. The BEST way to fix this is to get a TransGo Shift Kit for the 4L60E. It comes with a redesigned TCC system and new valve to go with it that will correct the problem (W/O replacing the VB) and keep it that way, PLUS it also fixes other problems that these units have that shorten the life of the tranny. This, along with 3-4 clutch failure and Sun Shell breakage is one of the most common problems encountered with these units. I do them all of the time.
If I do get the 1870 code would this be the correct kit?

TransGo Shift Kits ® 4L60E 93-up
# 35935 SK 4L60E Shift improvement / correction kit

and is the kit a fairly easy install?

Not sure of the number you have but as long as it says TransGo that is it. The hardest part of the kit is getting the Servo out and adjusted properly but it isn't that bad. I have even put these into high mileage trucks that you would swear were borderline slipping and when finished they shifted like they were brand new trannies. Now depending on the year you could potentially have a problem with the converter lining (being cooked) but if it is @97 up the lining is indestructable. Just remember that replacing the converter W/O putting this kit in WILL give you the same code IMMEDIATELY after driving.