I've got a 1998 4WD Blazer that I recently purchased. I noticed that it's leaking transmission fluid at highway speeds. At idle and it doesn't seem bad. I have checked the coolant lines and they are dry. I'm thinking that it might be coming from the front seal. Any suggestions? Thanks.

 

I can't tell you for sure Bryan, as I am in pretty much the same boat and posted almost the same question about my 97, but very good chance the answer is yes. Are you able to tell the source of the leak? Maybe hit everything with degreaser and a pressure washer and try to find out where its coming from. On mine its coming from the overfill/breather tube which is tied towards the top of the trans. dipstick.

 

96 and newer has a 2 piece case/bell housing. The bellhousing bolts onto the case. the bellhousing has 2 inspection plugs 1 large and 1 small one, located on the bottom side. a quick pick with a screwdriver and you can shine a light or inspection camera up in the holes to see the leak area. Front area leaks require removal and complete reseal. if it's a higher mileage unit, you might want to consider a complete teardown for inspection of damage.
Leaks from the vent tube are usually Torque converter/heat related and the transmission vents the expanded/overheated fluid. Scan the Vehicle for transmission codes, see if p1870 tcc slip exists. if it does a Gil-Younger (RIP) orange box shift kit usually fixes it. Tek-pack fitzall makes a tcc regulator valve that works as well. if it does not have any slip codes. try a transmission cooler for the heat.
Keep us posted

 

Update. I finally got the Blazer inspected and I was driving it back from the garage. I didn't have any smoke for about five miles. I was babying it for a little and then decided to take some back roads and get a little rough with it. I noticed a smoke cloud following me after a while. I only had a couple miles till I got home so I kept going. After another mile I noticed that I didn't have 3rd or overdrive anymore. I was able to manually shift from first and second but it would not shift up any more. At this point I thought that the transmission was toast so I nursed it home. I left it cool off for a half hour and took it out for another drive. To my surprise the transmission was working fine again. An error code was set though. I haven't had a chance to check to see what it is. I would think that it is a slippage code. I'm going to look up the shift kit that you recommended and see if that solves my problem. I'll keep you updated. Thanks again for your help!

 

I found this posted on another site:

This is a known issue with GM vehicles that have the 4L60E transmission. The issue normally presents itself after the transmission has had time to warm up and has been driven approximately 50 - 60 MPH. At highway speeds the torque convertor locks up for increased efficiency and so that it generates less heat. The lockup is accomplished by a solenoid in the tranmission's valve body which applies the torque convertor clutch (TCC). The solenoid and valve body itself are made of different metals which cause them to expand and contract at different rates. This constant variance in rates causes the valve body to wear away. The wore valve body allows transmission fluid to slip past the solenoid, causing a weak TCC apply. This weak apply is detected by the tranmssion as a slip. When a slip is detected the computer increases the line pressure to the shift solenoids to make the shifts firmer to minimize damage. This increased line pressure is what causes the hard shift that you feel, it is most noticable from 1st to 2nd gear. If the transmission detects the slip on two consecutive trips it will illuminate the "Check Engine" or "Service Engine Soon" light and store the code P1870.
If you ignore the problem, you will end up damaging your transmission and it will require a rebuild or replacement. However, if you catch it in time you can generally save your transmission. There are two ways to remedy the problem. 1) Replace the valve body. (GM has a new updated one) 2) Repair your current valve body, this can be done with special repair kit available through Sonnax.

 

3rd & 4th gears are a clutch set. The P1870 code you copied from the other site is a different section or system of the transmission. Remember the transmission uses several different hydraulic and electrical systems to accomplish all the gears and lock up. You may have multiple failures. P1870 & 3-4 clutch failure are at the top of the list. Also diagnosing from a remote location is harder to do. A seat of the pants/ hands on approach is always faster. We share expertise and our own experiences. Hopefully to lesson your aggravation and to speed up your repair.

Keep us posted

 

Tranzman,

I've been looking for the Gil-Younger (RIP) orange box shift kit that you posted about but I'm not able to locate it. Can you point me in the right direction? Thank you.

 

Update. I installed a ATP Automotive SK-3 Automatic Transmission Shift Kit. The transmission was working good again until it heated up. After 5 miles it started blowing transmission fluid out of the breather again. This time there was a small fire from it blowing out on the exhaust manifold. I'm thinking of trying a transmission cooler next. After that I'm to the point of a replacement. Any suggestions? Thanks.

 

Your trying to put a band aid on something that needs stitches. You will just spend more money than needed in the long run.

 

I have installed a transmission cooler and I've still got overheating problems. The cooling lines are hot to the touch. At this point I'm done messing with it. The next step will be a remanufactured transmission.