1997 Silverado Leak

1988GMC · July 27, 2016

Truck in question is a 1997 K1500 4x4, 350 Vortec, Auto trans, bone stock other than aftermarket wheels and tires. The truck was leaking fluid from somewhere in the vicinity of the front output shaft of the t-case. I replaced that seal, and u joints, but there is still a leak. The truck has a 2-piece front drive shaft, and it appears that the fluid is coming from the meeting point of the front and rear pieces of the shaft. Also if I apply pressure with my hand I can wiggle the drive shaft and the play seems to be coming from the same meeting point of the front and rear pieces of the shaft. There is also a vibration at highway speed. Any help or ideas would be appreciated. TIA

arcasey · July 27, 2016

How much of a leak? If it is very little it is likely from the original grease breaking down inside the slip joint of the front drive shaft. I am assuming that is what it is from your description of play at the slip joint on the shaft. The seal that keeps the grease in place has likely gone bad and you have play due to that. Those seals can be replaced, but no more than they cost, as old as that shaft is and as hard as it would probably be to get the pieces apart to fix the seal, I would just replace the whole shaft and the U-joints while I was at it.

Now, question about your highway vibration. Those front shafts (unless I am terribly mistaken and by that I mean my 96 K1500 does not) do not rotate unless the transfer case is engaged in 4 wheel drive. I am going to bet that your vibration is not from the front drive shaft. With that said if your vibration goes away from fixing/replacing the shaft please let us know.

Other things that may be causing your vibration: Bad tire, bad hub assembly, worn suspension components, worn/broken engine mounts, etc. I am replacing my front Hub Assemblies right now. Funny thing is I couldn't tell they were bad until I jacked the front of the truck up and spun the tire with my hand on the bumper to feel for the vibration. The tried and true method of checking for excess play lead me to believe that the hubs were fine because there was no play at all but i could definitely tell there was excess vibration in the bearing when turning the tire. Good luck on finding that vibration. I've got one I've been trying the find for about a year.

Colossus · July 27, 2016

Well we all start to leak, sooner or later

1988GMC · July 28, 2016

After looking further into it I don't think that's where the leak is at (where the two portions of shaft meet up). Although, I do agree with your broken down grease theory and the seal is definitely bad. Transfer case fluid level was fine, but transmission level was low. But the leak seems to be coming from that general vicinity (output shaft of transfer case). I'm puzzled. Any thoughts?

arcasey · July 28, 2016

I'll have to take a look under mine once I get it back and see what it could be. Been a while since I've been under mine and it's in the shop right now. Things that it could be without looking at it to see where the leak is coming from would be pan seal, front pump seal, or the front seal of the tranny.

Also, since it sounds like the leak is coming from the drivers side, have you checked to make sure that your power steering pump is not leaking as well? Reason I ask is some variants of power steering fluid can be reddish in color.

1988GMC · July 29, 2016

Ok that would be great. I'm pretty sure it's not a pan seal, or power steering. I don't think it's power steering because the oil mess does not make its way towards the engine. It ends about mid way up the front drive line.

1988GMC · July 30, 2016

I have found the leak. But I don't know what the gasket would be called. So the transmission mates up to a piece, which mates up to the transfer case. It's leaking between the trans and this mystery piece. The transmission mount bolts directly to this piece.

arcasey · July 30, 2016

I'm not positive but I believe the transmission output bolts up to the transfer case input. I still don't have my truck back yet to look at though lol. I think you may have a bad output seal on the transmission because I think the connection between the tranny and transfer case is a dry connection and with you stating that the fluid level in the T-case was okay but the tranny was low, that would be my guess. There isn't a real easy way to diagnose that.

1988GMC · August 5, 2016

Well I found my issue. It is not a seal but a large chunk has broken off of the transmission. It was a bolting point so you couldn't see it with it in the truck but as soon as I disassembled it, it was obvious. Anybody have a good recommendation for where to buy a tranny (4L60E)? I have heard to stay away from monster transmission...