Scheming against the inevitable diff leak repair - ZR-1 Net Registry Forums

billschroeder5842 · 01-02-2022

As most of us do (I'm actually pretty good at this) I'm scheming against the inevitable repair project and trying to out smart what I really know is the best course of action.

My latest obsession is a small seeping leak on the differential on my 91 with 85k between the bat wing and the carrier on the passenger side, in between the bracket for the rear control arm. This is seeping was found after I saw a 1/2 dime size drip on the floor. I cleaned up the differential, narrowed it down and re established its location after a 10 mile ride.

Now, a "normal person" would just keep an eye on it and wipe small seeping every couple of weeks, but I'm too emotional for that. I consulted the FSM and found that fixing this type of seep/leak is a PIA involving dropping exhaust, springs, C-Beams, half shafts bat wings....etc. This type of juice is hardly worth the squeeze, but it may be a winter project.

While searching the net I saw a couple of references to a possible cause being a clogged vent tube on the top of the bat wing that could increase internal pressure and force fluid out? That fix seems too easy but I need to check it out before tackling this project. Has anyone heard of such a thing?

Any other ideas?

1991 Corvette ZR-1 · 01-02-2022

Hi, Bill. Love the Russian Blue in the LT5 shot. If the diff has never been opened, chances are it is just time for a reseal. That unfortunately does involve dropping the diff for it. Never heard of the vent getting clogged up top. If anything, the pressure dispersed from that vent will keep any contaminants from sitting long enough to form a strong clog that could keep the pressure in.

I had less fortunate luck, my driver side half shaft yoke seal was toast even before I purchased the car. I put it off as long as I could until I got tired of seeing wet grime. I ended up replacing the stock gears with a 3.90 Yukon set and had the whole thing rebuilt. If you are stock and keeping it that way regardless, while it is out, it could be a good idea to just have it rebuilt. Imagine going through all that trouble to reseal, then 3 or 4 thousand miles later you get a leak that requires a rebuild.

But that is just the method of my madness, plus mine was a higher mileage car. Yours seems like you will be keeping it for a very long time. If someone is keeping theirs forever and it has some miles, I do not see the harm in going through components or a system completely so it is as good as new. They are antiques at this point.

And you are right, winter is the best time to do a project like this. I did mine last summer and got a wicked heat rash on both forearms after army crawling through diff fluid and dirt on the garage floor while sweating for hours doing the job. Heat rash is no fun, the more you itch, the better it feels?but the more it itches and burns as a result.

billschroeder5842 · 02-26-2022

Well, it looks like my seeping continues to come from the passenger side seal. I get some drips on the floor after every drive and just "living with it" and wiping it off is probably not going to work. I did review some records and found that in '92 the differential seal was replaced under warranty, hence all the squishy rtv-ish sealant coming out the side.

I'm typically one to dive in and do it myself, I've read the FSM and watched a few videos. I am worried that my infrastructure may be lacking as I would be tackling this on my garage floor with some car jacks and typical tools.

Anyone else done this in their garage without a lift? I'd hate to have a pro do it (due to lack of tools) but I don't want to get started realize I'm in over my head only to have compounded my problems.

Any advise or tips? The FSM and YT videos are often at odds with how to tackle this one.

Thanks!

WARP TEN · 02-27-2022

Bill, is there any chance you could stop the seeping by just going around and re-tightening every bolt? Kind of like the problem of leaking from the oil pan. Or have you done this already? My next bit of advice is, if it were mine, I would send it straight to Marc Haibeck for the repair, or someone experienced with ZR-1s nearer you. But that is just me. Marc and Bob did two rears for me and in each case upgraded them to 4.10s. Reasonable cost and no hassle to me. Naturally, everything was done perfectly by two people who have done this hundreds of times. Just a thought.... --Bob

01-02-2022	#1
billschroeder5842 Join Date: Nov 2016 Location: Southlake, TX Posts: 584	Scheming against the inevitable diff leak repair As most of us do (I'm actually pretty good at this) I'm scheming against the inevitable repair project and trying to out smart what I really know is the best course of action. My latest obsession is a small seeping leak on the differential on my 91 with 85k between the bat wing and the carrier on the passenger side, in between the bracket for the rear control arm. This is seeping was found after I saw a 1/2 dime size drip on the floor. I cleaned up the differential, narrowed it down and re established its location after a 10 mile ride. Now, a "normal person" would just keep an eye on it and wipe small seeping every couple of weeks, but I'm too emotional for that. I consulted the FSM and found that fixing this type of seep/leak is a PIA involving dropping exhaust, springs, C-Beams, half shafts bat wings....etc. This type of juice is hardly worth the squeeze, but it may be a winter project. While searching the net I saw a couple of references to a possible cause being a clogged vent tube on the top of the bat wing that could increase internal pressure and force fluid out? That fix seems too easy but I need to check it out before tackling this project. Has anyone heard of such a thing? Any other ideas? __________________ Bill Schroeder Texas Proud! 1991 Corvette ZR1 #1388 2015 Challenger Scat Pack Shaker Last edited by billschroeder5842; 01-02-2022 at 02:11 PM.

01-02-2022	#2
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 297	Re: Scheming against the inevitable diff leak repair Hi, Bill. Love the Russian Blue in the LT5 shot. If the diff has never been opened, chances are it is just time for a reseal. That unfortunately does involve dropping the diff for it. Never heard of the vent getting clogged up top. If anything, the pressure dispersed from that vent will keep any contaminants from sitting long enough to form a strong clog that could keep the pressure in. I had less fortunate luck, my driver side half shaft yoke seal was toast even before I purchased the car. I put it off as long as I could until I got tired of seeing wet grime. I ended up replacing the stock gears with a 3.90 Yukon set and had the whole thing rebuilt. If you are stock and keeping it that way regardless, while it is out, it could be a good idea to just have it rebuilt. Imagine going through all that trouble to reseal, then 3 or 4 thousand miles later you get a leak that requires a rebuild. But that is just the method of my madness, plus mine was a higher mileage car. Yours seems like you will be keeping it for a very long time. If someone is keeping theirs forever and it has some miles, I do not see the harm in going through components or a system completely so it is as good as new. They are antiques at this point. And you are right, winter is the best time to do a project like this. I did mine last summer and got a wicked heat rash on both forearms after army crawling through diff fluid and dirt on the garage floor while sweating for hours doing the job. Heat rash is no fun, the more you itch, the better it feels?but the more it itches and burns as a result. Last edited by 1991 Corvette ZR-1; 01-02-2022 at 06:36 PM.

02-26-2022	#3
billschroeder5842 Join Date: Nov 2016 Location: Southlake, TX Posts: 584	Re: Scheming against the inevitable diff leak repair Well, it looks like my seeping continues to come from the passenger side seal. I get some drips on the floor after every drive and just "living with it" and wiping it off is probably not going to work. I did review some records and found that in '92 the differential seal was replaced under warranty, hence all the squishy rtv-ish sealant coming out the side. I'm typically one to dive in and do it myself, I've read the FSM and watched a few videos. I am worried that my infrastructure may be lacking as I would be tackling this on my garage floor with some car jacks and typical tools. Anyone else done this in their garage without a lift? I'd hate to have a pro do it (due to lack of tools) but I don't want to get started realize I'm in over my head only to have compounded my problems. Any advise or tips? The FSM and YT videos are often at odds with how to tackle this one. Thanks! __________________ Bill Schroeder Texas Proud! 1991 Corvette ZR1 #1388 2015 Challenger Scat Pack Shaker

02-27-2022	#4
WARP TEN Join Date: Apr 2007 Location: Lake Bluff, IL Posts: 2,045	Re: Scheming against the inevitable diff leak repair Bill, is there any chance you could stop the seeping by just going around and re-tightening every bolt? Kind of like the problem of leaking from the oil pan. Or have you done this already? My next bit of advice is, if it were mine, I would send it straight to Marc Haibeck for the repair, or someone experienced with ZR-1s nearer you. But that is just me. Marc and Bob did two rears for me and in each case upgraded them to 4.10s. Reasonable cost and no hassle to me. Naturally, everything was done perfectly by two people who have done this hundreds of times. Just a thought.... --Bob __________________ 2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough"