Transmission Leak, wiring harness?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

GLS0628

Newbie
Joined
Feb 14, 2015
Messages
5
Reaction score
0
I have a 1996 c1500 with auto transmission. I starting getting a transmission fluid leak only when the truck sits for a couple days. It does not leak when I drive it daily. I had someone replace the pan gasket even though I did not see any evidence that it was leaking from there. I had the same person look at it a couple more times never finding the source of the leak. He says the only place that it could be coming from is through a wiring harness on the transmission. I don't have very much faith in this person after the first repair due to some comments that he made that just did not make any sense, such as him replacing the gasket allowed the fluid to get high enough to leak somewhere else or it allowed enough pressure to build up to force it to leak somewhere else. Neither I believe. Has anyone heard leaking from harness or do you think that it is possible?

thanks,
GLS
 

Wade

I'm Awesome
Joined
Dec 4, 2017
Messages
269
Reaction score
151
Location
Wisconsin
That explanation sounds a little hokey to me. . . It could be leaking from a sensor on the trans, like the speedometer sensor. Maybe running down the harness. How much fluid do you lose?
 

df2x4

4L60E Destroyer
Staff member
Super Moderator
Joined
Mar 1, 2012
Messages
11,149
Reaction score
12,672
Location
Missouri
Leaking through the wiring harness (or more specifically the plug for it that goes into the trans case) is absolutely possible with a 4L60E or 4L80E, not sure about others but that should cover the auto options for a '96.
 

96dually454

Newbie
Joined
Mar 20, 2017
Messages
10
Reaction score
9
Location
Portland
Agree with df2x4. Those plugs where the wires pass thru the trans case are known for leaking.
GM sells the replacement harness and o-ring setup to stop that leak. They can leak driving or sitting. Unfortunately the pan must be removed again to replace the harness.
 

skylark

I'm Awesome
Joined
Nov 15, 2011
Messages
7,836
Reaction score
7,646
Location
Grants Pass, OR
They leak when sitting because the tranny pump isn't pumping the fluid down to its normal operating level so the fluid level is higher.
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,963
Reaction score
13,743
Location
The Seasonally Frozen Wastelands
They leak when sitting because the tranny pump isn't pumping the fluid down to its normal operating level so the fluid level is higher.
In other words, it takes a while for the torque converter fluid to drain back into the pan. When it does, the fluid level gradually goes up, and all sorts of seals that would be above fluid level when the engine is running...aren't any more.

I've seen lots of similar fluid leaks on other transmissions--modulator valve o-ring, shift shaft seal, dipstick tube O-ring (or dipstick tube cracked at the O-ring groove), tailshaft seal, Kickdown or throttle-valve cable housing o-ring, etc.
 

GLS0628

Newbie
Joined
Feb 14, 2015
Messages
5
Reaction score
0
Okay time to get back to this problem. It certainly has to sot a couple days for it to leak. Parking spot at work has no drip and it has been 5 days a week for over a year. It is coming from the drivers side. i can see 2 supply lines and the dip stick and none of the 3 are leaking. There is a shield that is blocking view. I assume this is a heat shield between the catalytic converter and transmission. Do you think that it will be okay to take the shield off and drive without it so i can inspect after a couple days?
 
Top