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Differential Leak at Driveshaft - Diff Brace Issue?
Was installing my shiny new rear diffuser and saw a fat drop of oil on my sway bar. The seal at driveshaft has a small leak, and my diff bushing is starting to bulge (see pic). This is a recent issue as I installed a Bell differential brace at 107k in August, re-torqued it after 1000 miles. Everything was dry then and the rear bushing was not bulging. I am at 114k now, this is also really just normal wear, yes? I drive hard, this is my 2nd G37x and it really is one of the best cars I have ever owned. I'm 53, and have owned a bunch.
What were the labor hours/cost? Not trying to get on my back to change out bushings...
I'll upgrade to a solid rear diff bushing, and can anyone identify all the parts I will need? See below diagram-
I will drain and change diff fluid tomorrow, see how much has leaked. Thanks, advice/insights appreciated
Last edited by ChefMatt; 12-03-2021 at 04:31 PM.
Reason: Additional info
yes I had that issue as well. I also have the same diff brace as you
I think it's leaking from where the diff seals in the front where it bolts to the driveshaft. Maybe because it is now solidly mounted and when the rest of the driveline moves around, it kind of yanks the diff to the point where the seal gets a little opened up and spews some fluid
Interesting... I have never liked the idea of bolting one side of the differential to the subframe.
Bushings serve an very important function to reduce shock loads...a diff brace effectively "welds" the rear of the diff to the subframe (but just on one side!!)
From my experience, a weeping diff pinion seal is not a common issue, so you both may be onto something.
What is common is for the diff cover to leak after the brace, the loosening and retightening of these bolts can crack the RTV seal. It happens to some folks when they change their hardware on timing covers.
Since there's liquid gasket holding it is really easy to break the seal.
Just like Sonic stated pinion leaks are not common and it's possible the drivers bushing on the diff has taken some beating causing the diff to shift a bit changing your differential resting angle.
It could all be tired bushings either way that pinion seal is fun work. You may want to just source a differential and swap it. X differentials should be more common than manuals.
Interesting... I have never liked the idea of bolting one side of the differential to the subframe.
Bushings serve an very important function to reduce shock loads...a diff brace effectively "welds" the rear of the diff to the subframe (but just on one side!!)
From my experience, a weeping diff pinion seal is not a common issue, so you both may be onto something.
Originally Posted by BULL
What is common is for the diff cover to leak after the brace, the loosening and retightening of these bolts can crack the RTV seal. It happens to some folks when they change their hardware on timing covers.
Since there's liquid gasket holding it is really easy to break the seal.
Just like Sonic stated pinion leaks are not common and it's possible the drivers bushing on the diff has taken some beating causing the diff to shift a bit changing your differential resting angle.
It could all be tired bushings either way that pinion seal is fun work. You may want to just source a differential and swap it. X differentials should be more common than manuals.
Thanks you for the input! I had the same feeling that the pinion seal weeping is not a common issue. For sure my diff is tired from taking my daily beatings, but when I installed the diff brace in August the rear bushing was smooth, not cracked at all really, and for sure no bulge like it shows in the recent picture.
I thought about just swapping in a used oem X diff, and briefly looked at a new Z1 diff with better gearing. I would have to change the transfer case as well and don't want to go down that rabbit hole. Also the new parts are coming today (Pinion seal, bearing, Z1 bushing set, new fill plugs). I am considering leaving off the Bell brace after this rebuild.....thoughts? That diff brace is really one sweet mod, I felt it made a big difference in getting power down to the rear wheels. The bushing by itself will be somewhere in-between?
My mechanic is charging me 1000.00 labor to do the Pinion seal and bearing, bushing install, and swapping my front shocks (installing KYBs on same OEM springs). That seems pretty fair, and something I don't want to tackle myself in any case. Doing the rear shocks tonight myself.
Well good news and bad.
Bad news is more than likely the brace killed the main bushing which is common and the minute they get a small tear that's the end of them.
Good news is that bushings will get you set
Having an extra diff can come in handy, you could turn the spare diff into a LSD with some unorthodox parts(phantom grip), gearing on the X can be an issue due to availability of parts and to my understanding only GTR front gear/pinion is the only one you can use which means the rear has to match as well. Rabbit hole indeed.
On another note I've seen documentation of members having difficulty with the brace not lining up with the diff (unsure about quality control) and this could be the case.
I wonder if these braces were made with a donor with decent bushing life or was it made with solid bushings as these are a huge factor with alignment and since there's only one bolt holding the rear there is movement back there.
The template of these braces is made once and I'm sure they did their initial test on a couple of vehicles and that was it, onto production. Quality control can show bad batches
I suggest once the bushings are in place that the diff is bolted and the alignment of the brace is checked as it could be off. This will be the true test as bushings should have it where it needs to go, the brace is intended to to prevent any extra movement from it's natural position.
My rear diff bushing was already blown when I purchased the car last year. I added this brace and filled the bushing with some epoxy that Frank recommended.
Brace was installed 6k miles ago.
Epoxy filling 3k miles ago.
Well good news and bad.
Bad news is more than likely the brace killed the main bushing which is common and the minute they get a small tear that's the end of them.
Good news is that bushings will get you set
Having an extra diff can come in handy, you could turn the spare diff into a LSD with some unorthodox parts(phantom grip), gearing on the X can be an issue due to availability of parts and to my understanding only GTR front gear/pinion is the only one you can use which means the rear has to match as well. Rabbit hole indeed.
On another note I've seen documentation of members having difficulty with the brace not lining up with the diff (unsure about quality control) and this could be the case.
I wonder if these braces were made with a donor with decent bushing life or was it made with solid bushings as these are a huge factor with alignment and since there's only one bolt holding the rear there is movement back there.
The template of these braces is made once and I'm sure they did their initial test on a couple of vehicles and that was it, onto production. Quality control can show bad batches
I suggest once the bushings are in place that the diff is bolted and the alignment of the brace is checked as it could be off. This will be the true test as bushings should have it where it needs to go, the brace is intended to to prevent any extra movement from it's natural position.
Good points, I didn't think of replacing the diff with a used OEM, only rebuilding current one. I just checked ebay and there are tons of X rear diffs for 250-400, some with low miles. In any case, I think I will leave off the brace after rebuild, see if I notice a difference.
Prior to pulling the plug on an online sale check your local yards to see if there is a local one. The diff weights about 75lbs so if you can avoid shipping it should save you a couple of dollars.
In all honesty I think the brace will be fine as long as it's all installed together.
Prior to pulling the plug on an online sale check your local yards to see if there is a local one. The diff weights about 75lbs so if you can avoid shipping it should save you a couple of dollars.
In all honesty I think the brace will be fine as long as it's all installed together.
Update - About 2 wks after the pinion seal bushing repair (along with Z1 bushing install) it's leaking again. Took it back to the shop, they put it right up and confirmed the repair didn't hold. Going shopping for a AWD rear diff on ebay, any more advice? Other than to look local? I have 117k on this G, planning on keep til 200k at least. Is a Z1 diff worth it? Thoughts?
Update - About 2 wks after the pinion seal bushing repair (along with Z1 bushing install) it's leaking again. Took it back to the shop, they put it right up and confirmed the repair didn't hold. Going shopping for a AWD rear diff on ebay, any more advice? Other than to look local? I have 117k on this G, planning on keep til 200k at least. Is a Z1 diff worth it? Thoughts?
12-03-2021 | 04:02 PM
