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Where is this transmission fluid leaking from?

29K views 42 replies 7 participants last post by  reginoc58rc 
#1 ·


This picture is taken looking toward the front left of the truck. I believe that case at the top is the center differential.. but what could cause this fluid leak. I'm about to try a transmission rebuild on this thing and would like to solve this leak while I'm at it.
 
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#6 ·
Yeah, once you said it was the transfer case I was able to find a input shaft seal and output shaft seal for the case at RockAuto. I guess that is their terminology for the one that goes to the front driveshaft and the rear driveshaft. Both seem to be leaking a lot of fluid.

Next problem I ran into is I'm trying to get the front driveshaft removed but cant access the retainer bolts on the transfer case side. So I'm trying to remove the crossmember. I've taken off the two nuts and bolts on both sides of the frame and the two nuts in the middle that attach to the transfer case bushing, but its barely budging.
 
#7 ·
There is also a paper gasket that fits between the transmission extension and the transfer case (which is what looks like is the part leaking on yours). There is an input seal to the transfer case on the input shaft of the transfer case you will see once you get the transfer case out. That would not cause leakage to the outside of the unit if it was leaking. If it was bad it would allow fluid to leak from the transfer case into the transmission and vise versa. The output seals for the transfer case would be the seals to each driveshaft.

You may know this, but I'll tell you just in case you don't: You have to support the transmission when you remove the crossmember. You should be able to get the front driveshaft off without taking the crossmember out.
 
#8 ·
I'm getting a little more than I bargained for with this one. The previous owner did some mudding so I'm getting sand in my eye with every turn of the ratchet, etc.
Once I lifted the transmission the crossmember came out pretty easy. I may have lifted it too far because that transfer case/ transmission gasket started leaking more once it was up. If I do this again, I'll use the pry bar as much as possible against the bushing to keep from straining the bolts between the transfer case/ transmission.

On that front driveshaft, I got the front side free but the transfer case side is still stuck.

Any ideas?
Also the front axles don't have to come out for the transmission to drop do they? Sorry about all the questions, my service manual is in the mail.
 
#9 ·
Take the (4) 11mm head bolts (i think that is the size they are) holding the front u-joint to the yoke and it should come right out (you may have to pry a bit with a screwdriver). Be sure not to allow a u-joint cap to fall off and knock the needle bearings out of place. The front axle does not have to be removed to take the transfer case out.
 
#10 ·
I pulled the pan yesterday and found this:

About 8 paper towels worth of sludge there.

My manual came yesterday and evidently there were three transfer cases used in 1994:
NP 241
Borg Warner 4401
Borg Warner 4470
The NP case has a square fitting for the front drive shaft while the BWs have a round one. You can tell the 4401 from the 4470 because the 4401 has splines going lengthwise along the case. The 4401 is pictured.

I'm still not sure what the adapter to the left of the case above is called. I did find why it was leaking though. There was just a silicone bead instead of a gasket on the transfer case side of the adapter and the transmission side was missing two of the 4 15 mm (?) bolts. People like me without pneumatic tools will need ratcheting wrenches for those 4 bolts and the 6 15mm oneson the transfer case side as well.
 
#11 ·
Evidently you can't edit your posts on this forum but that piece to the left is called the extension housing official, or tailshaft housing. But it is considered part of the transmission, not the transfer case. Also both of the other posters were right. There is a seal on the transmission side and a gasket on the transfer case side. The gasket was missing and the seal needs to be replaced pretty bad. Anyway, on to the rebuild...
 
#16 ·
Ok I found the transmission lines will have to be removed before the torque converter can be unbolted from the flexplate. The lines are literally right in the way of where a full turn of the wrench would be. Problem is someone has obviously been into this transmission before and rounded off the flare nut to the point that it looks round. Also this is a pre-1998, so it just a flare nut. After that, they went to a e-clip supposedly.

The big nut looks to be about 19 mm and the flare nut above it can be got onto with a 14mm but its so rounded the flare wrench just spins. Edit: Evidently it is a 1/2" nut, not a 14mm.
 
#17 ·
You will not be able to remove the line by spinning/looseing the bigger adaptor that goes into the transmission housing. You will destrot the line trying that. You could always cut the line and use a double flare tool with some new ends to put it back together. You will have to do that anyhow if you plan on replacing the nut that is already stripped (although not in the same location on the line).
 
#18 ·
Thanks for that heads up. I guess those flare nuts weren't as rounded as I thought. I was hesitant to buy a fractional line wrench set but thats what it took and the nuts came right off. On to the next (and hopefully last) problem. Unbolting the flexplate from the torque converter. I read somewhere that there is an inspection plate that can be removed on the bottom bell housing on the 98 and later 4l60es. But this is all I got, the starter hole:

There is a small hole that can be used to rotate the flexplate with a flathead shown here:

Pretty sure it takes a 15 mm but a box end won't slip in there. And the raised edge of the starter hole makes a straight open end wrench almost impossible to get a full turn. Does someone make an offset open end wrench and would that be necessary?
 
#20 ·
Thanks for the help guys, especially ASTE. Heres the beast on the table. With the torque converter off, it was very liftable onto my table.



So here are the tools I would pick up to remove a 4l60e on a 94 k1500:
SAE line wrenches for cooler lines
Metric ratcheting wrenches for extension housing bolts
5/8 deep well socket for crank pulley bolt and 14mm deep well socket for bell housing to block bolts
transmission jack and floor jack
2 pairs 6 ton jack stands
OEM gasket with six bolt holes mentioned above
Flywheel turner in case your friends' backs start acting up when its time to remove those flywheel to torque converter bolts :roll: http://www.tooltopia.com/kd-tools-2270.aspx
 
#22 ·
Glad to hear you got it out. When you go back with it, remember to get the torque converter seated in the pump all the way. You should not be able to put your fingers between the transmission pump and the converter when it is all the way seated. If you do not get it seated all the way you will mess the pump and possible the converter up.
 
#23 ·
Well I have been taking my time on this rebuild. I found another possible cause of this massive fluid leak, a really bad front pump bushing:

Also I had 4 stuck valves in the valve body. One was maybe the most important, the AFL valve. Anyway I will let you know what happens when I put it back together.
 
#26 ·
Sorry about the pic, can't find the cord for our digital camera, had to take it from a phone. One tip I have for a rebuild is, make sure you have the part you want to replace in your kit before you tear apart the old one. This happened to me on the forward accumulator piston o-ring and now I have to wait for the Chevy dealership to open to start assembling it all.
 
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