Transmission leaking by wire harness?!?

[Matt Bachand]

It really appears that my tranny is leaking in the back by the bracket towards the transfer case right wehre the main wire harness goes in.

I didn't want to touch it and make it worse until I learned about it more. What type of seal is this?

 

[Missy Good Wench]

There is an electrical plug/bulkhead that goes through the case.
A bundle of wires plug into the inside and then the plug goes into the unit from the outside.

The bulkhead fitting has an O ring on it where it goes though the case.

Possibly the O ring or maybe a cracked bulkhead.

Missy

 

[Matt Bachand]

There is an electrical plug/bulkhead that goes through the case.
A bundle of wires plug into the inside and then the plug goes into the unit from the outside.

The bulkhead fitting has an O ring on it where it goes though the case.

Possibly the O ring or maybe a cracked bulkhead.

Missy

Ok, so I pull apart the wire=harness and I should be able to tell whats going on then.

Either of them seem like an easy fix then missy?

The bulkhead is the plastic fitting on the wire harness, NOT the case right?

 

[mattthebrat]

I had this problem on my tranny, when they rebuilt it, they had to order a whole new wiring harness, not sure if that is the case or if I just got soaked.......

 

[THEFERMANATOR]

The ALLISON and 4L60E use the same style plug and unternal harness. They don't leak as often, but they do leak ocassionally. Fortunatley the 4L80E one can be had for pretty cheap as it was also used as an upgrade for 91-93's as they had a different style that was pretty failure prone and the 94+ style's price came down because it was the correction.

 

[davo727]

Transtar industries Inc has everything for auto trans including your harness.

http://www.transtar1.com/electrical.asp

 

[Detroit Dan]

I changed that o-ring on mine, had to get it at the dealer but it was cheap. IIRC it is at the front drivers side of the tranny? Maybe I'm remembering it wrong because I was underneath it looking up...

 

[Matt Bachand]

The ALLISON and 4L60E use the same style plug and unternal harness. They don't leak as often, but they do leak ocassionally. Fortunatley the 4L80E one can be had for pretty cheap as it was also used as an upgrade for 91-93's as they had a different style that was pretty failure prone and the 94+ style's price came down because it was the correction.

How does this come apart? I don't want to break it as it seems pretty important considering the amount of wires that pass through it!

Also, if its not the o-ring if the bulkhead is cracked I need a whole new wire harness?

 

[Missy Good Wench]

OK here is the real deal.

There were running changes in the production con figuration of the plugs used on the 4L80 wiring harness

The later style harness on the truck has a round plastic outer shell that the wires go into.

There are some little "Gripper" spots on opposite sides of the thing. When squeezed the plug can then be pulled off.

Older ones I believe had a screw in the middle of the thing between the wires ??????

OK
The "Bulkhead" that protrudes theough the tranny case is part of the internal wiring harness.

This is not the end of the world.

Remove the pan. The harness plugs into various spots around the valve body.

Note where the wires go. Some plugs may be a one spot only and others (solenoids) may not be.

The wiring harness likely should be replaced.

The Bulkhead comes from the inside out. Once the harness from the chassis is unplugged you will see 3 plastic prongs


**** be careful with the harness plug on the chassis wiring****

These can and do break when fooled with.

The good part is that there is a replacement "Pig Tail" that can be spliced into the harness (All color coded "Piece of cake"

Now back to the tranny bulkhead

The assembly snaps into the case and the 3 prongs "latch" it in place.

The possibilities are Two (2) either the O ring on the Bulkhead is bad or the plastic bulkhead itself is leaking past a connector or maybe cracked.

Compressing the plastic prongs will allow the bulkhead to be pushed through into the case and the whole internal harness then is free to be removed.

Just make note of the plugs, wire colors and where they go.

This is an easy fix.

Clean the case out good where the fitting goes through. Lube the new Oring and push the new harness through until the prongs snap into place.

Plug the new harness in as needed and your done.

Good time to replace the filter and wash out the pan.

If the tranny has some time on it, you will probably see some dark gray stuff in the very bottom of the pan. This is normal as long as there is not black flakey stuff or metal particles.

Replece the filter, install a new gasket and replace the pan.]

Fill with tranny fluid to the add mark. run engine and cycle the selector lever through all the ranges slowly from one to the next. Set Park brake, place selector in "N" and check oil level.

Add fluid to bring level to just above ADD when cold. Allow to warm up good and recheck.

If level is good, your set.

The harnesses as I mentioned saw some changes. be sure to get a replacement harness that is the same as your old one.

The chassis pig tail harness replacement is NOT CHEAP from MA General.

I bought a New one off ebay for $30 and was jumping for joy. At the GM store they are about $200.

I can't tell you what the inner harness goes for but likely the tranny parts suppliers can provide these cheaper than GM does.

Hope this helps.


Missy





A

 

[Missy Good Wench]

In thinking back, I believe the wiring plugs inside the tranny are all different so that they can't get swapped around.

Just Plug and play ya know


Missy

 

[THEFERMANATOR]

There are 2 tabs that you squeeze together to unplug the harness. Then you drop the pan and find a socket the fits the plug that comes out of the tranny tightly(1 1/8" I think it is) and slide the socket over the stub sticking out and it will squeeze in the retaing tabs so that you can pull the stub out from inside of the trans. The o-ring's do leak every once in awhile, but if it is wet inside of the plug where the actual terminals are it is the harness bulkhead leaking and you will need to replace the internal trans harness.

http://cgi.ebay.com/ebaymotors/ACDE...r_Truck_Parts_Accessories?hash=item22ffeb2c9f

Or a cheapy.
http://cgi.ebay.com/ebaymotors/NEW-...r_Truck_Parts_Accessories?hash=item19b6d369ff

 

[Matt Bachand]

Thanks guys. This is why I asked, I would have tried to unplug it from the outside.........

Guess I'll leave this one alone till next summer when I'm due for a pan drop/filter/synthetic changeover.

My tranny was rebuilt 25,000 miles ago, so next summer will be right around 30k ish....... Good time for all that jazz..................

 

[Missy Good Wench]

I remember making a tool from aluminum that does the thing with the 3 prongs.

Done a few things with the 4L80 but have not had one all the way apart as yet.

Basically a Th400 with some extra parts for the OD and of course the electronic shift controls and pressure controls.


If the leak is not too bad, next summer will probably be fine for the repairs.


Missy

 

[Missy Good Wench]

Here is the internal wiring harness.
This is an ebay link. The guy selling this is an oK fellow. I have done buisness with these guys. (about 30 minutes from me)

Ebay number 4599547175

$45 and some change plus shipping. Not at all bad


Missy

 

[Detroit Dan]

Missy, where did you get checking it in neutral from? I've always done mine in park, trans up to temp. I thought neutral was specifically a Dodge/Chrysler transmission thing.

 

[Sparky8370]

If it is the same as the allison, mine was leaking too. Only when unplugged though. I cleaned it off and plugged it back in. Probably been 6000 miles now.

 

[Mudbath]

The harness inside has plugs for the Manifold pressure switch, EPC solenoid, TCC solenoid, 1-2 shift solenoid and 2-3 shift solenoid. The only two that you have to be careful with is the 1-2 and 2-3 shift solenoids as they can be switched. They are color coded IIRC.

 

[Missy Good Wench]

Most trannies dont circulate fluid in Park.

This is a technique I was taught back in the dark ages (70's)

Just stayed with it as it was always a fail safe way to do it.

Run the box through all the ranges to fill things up and purge any air out.

Again, training from ages past.
Many of the newer boxes may be different now.

If I come out in the morning after my 94 Burb has sat for a few days, the tranny will not drop right into drive unless I go to N first and allow things to fill.

Likely there is an internal leak allowing some drain back from the converter.

Aways had great success doing it this way ??????????/


Missy

 

[mattthebrat]

Most trannies dont circulate fluid in Park.

This is a technique I was taught back in the dark ages (70's)

Just stayed with it as it was always a fail safe way to do it.

Run the box through all the ranges to fill things up and purge any air out.

Again, training from ages past.
Many of the newer boxes may be different now.

If I come out in the morning after my 94 Burb has sat for a few days, the tranny will not drop right into drive unless I go to N first and allow things to fill.

Likely there is an internal leak allowing some drain back from the converter.

Aways had great success doing it this way ??????????

I don't have any leak problems with mine, but that is always what I do after a rebuild or a f/f change, run it through all the gears, and let it sit in neutral, recheck/topoff, and then do it all again before the truck ever moves.

 

[daustin]

I thought the trans dipstick was stamped on it "check in park engine hot" or something like that. If i do a drain & refill I always cycle through all the gears, Neutral as well and then check back in park..etc until it's full and warmed up.
Don