Can I replace my rear diff cover without dropping the sub frame?

[BigDave]

I have severely worn rear diff bushings I finally figured out. The bushing material has crumbled and is falling apart. I have already bought a new Genuine BMW cover with fresh bushings and a new paper gasket. Can I replace the cover without dropping the sub frame?

I have a 2005 cabrio and my trunk seems to be in the way for some of the top most fasteners. I have not found a single DIY so far addressing my question.

BTW, I just had my subframe out 18 months ago to replace five bushings.... The single front diff and the four main bushings. I had no idea the rear diff bushings should have been attended to at the time. I very much do not want to drop the sub frame again so soon.

[Cubieman]

I have severely worn rear diff bushings I finally figured out. The bushing material has crumbled and is falling apart. I have already bought a new Genuine BMW cover with fresh bushings and a new paper gasket. Can I replace the cover without dropping the sub frame?

I have a 2005 cabrio and my trunk seems to be in the way for some of the top most fasteners. I have not found a single DIY so far addressing my question.

BTW, I just had my subframe out 18 months ago to replace five bushings.... The single front diff and the four main bushings. I had no idea the rear diff bushings should have been attended to at the time. I very much do not want to drop the sub frame again so soon.

No, you do not need to drop the SF to remove the diff. cover. It may be difficult to reach some of the bolts and or/the rear diff. torx bolts in which case I use these:

https://www.harborfreight.com/3-piec...saAlI9EALw_wcB

I just put in CMP SF bushings which makes the space between the vehicle and the diff. bolts even less. I used those socket caps from harbor freight and 9/16"s wrench with the wrench inside of a piece of steel pipe in order to put the proper 90° of angle on the rear diff mounting bolts.

[Kdubski]

It's probably much easier to just drop the diff (undo sway bay, driveshaft (6 bolts) and axles 12 bolts). If you're replacing the cover, you'll need to apply gasket maker and let it cure. Using the OEM gasket material, it is recommended to keep dry (empty diff unless stood on driveshaft flange) until it is cured (24 hrs or so).

[Cubieman]

I used gasket maker (Drei Bond?) and was able to easily replace the cover with stock subframe bushings and sway bay out of the way.

I. know have CMP subframe bushings which decrease your working space even more and I was able to get to all the bolts.

You likely won't be able to get a torque wrench on the top most cover bolts is the only real downside of replacing the cover in situ.

[BigDave]

Thanks. We took the rear anti sway bar out. Removed the rear E14 torx bolts. They were new 18 months ago. The upgraded versions, of course.
We left the front mount bolt in.
The diff swung down far enough to remove and replace the cover.
The OEM cover had NO sealant on it. Only a paper gasket. I could not justify the expensive BMW sealant. So I bought some Permatex sealant specifically made to resist differential gear oil. And an OEM paper gasket.
Permatex 81182 Gear Oil RTV Gasket Maker, 3 oz.

https://www.amazon.com/gp/product/B0030MQAQI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I used a THIN a coat as possible and pressed the paper gasket in place on the cover. Then another thin coat on the exposed side of the paper gasket. Bolted everything up. MINIMAL excess sealant got squeezed out.

NO desire or need in this case IMO to wait a full 24 hours since I was not using just sealant alone. We waited two hours and filled it up with Liqui Moly 75W-140 with friction modifiers for LSD. LM20042

https://www.ecstuning.com/b-liqui_moly-parts/fully-synthetic-limited-slip-differential-fluid-75w140-1-liter/lm20042~liq/

The cover bolts got 35 ft lbs
The top two mount bolts got a HEFTY amount of stank. I think they called for 130 ft lbs. Torque wrench not possible. But NOT worried. I'll check them periodically. But, I think all is good there.

The bushing fix solved EVERY shifting and noise issue I had. Some of the issues have been around for YEARS~!! Everything is so great again. Those bushings must have been failing for years!!!! I blamed all my drive line issues on a half a dozen other imaginary reasons including a bad diff. Turns out my diff is FINE!!
Tranny is FINE!!

No leaks, of course.

[bigjae46]

I used a paper gasket and RTV...it leaked.

I just use the Permatex black RTV. Haven't had an issue. You DO HAVE to clean out the bolt holes where the rear cover bolts go into. If you leave enough RTV in the hole you can crack the case. That goes for any blind hole.

Maybe I have a lot of practice but I found it easier just to take the diff out. I had to take off the driveshaft to get the diff to rotate down more. At that point...might as well full remove it. I wanted the RTV to cure 24 hours to make sure I don't have a leak.

I guess if I just used a paper gasket then I wouldn't have to remove the diff. Hmmm....

[Cubieman]

I used a paper gasket and RTV...it leaked.

I just use the Permatex black RTV. Haven't had an issue. You DO HAVE to clean out the bolt holes where the rear cover bolts go into. If you leave enough RTV in the hole you can crack the case. That goes for any blind hole.

Maybe I have a lot of practice but I found it easier just to take the diff out. I had to take off the driveshaft to get the diff to rotate down more. At that point...might as well full remove it. I wanted the RTV to cure 24 hours to make sure I don't have a leak.

I guess if I just used a paper gasket then I wouldn't have to remove the diff. Hmmm....

I used gasket maker and didn't remove the diff., I applied the gasket maker,it was either loctite 5970 or Drei Bond, anyways after that I situated the diff. cover away from the diff. by ~1" by using a few of the long or medium length cover bolts threaded in ever so slightly.

This allows you to use gasket maker and then have the cover lined up and press it straight on.

[BigDave]

I used a paper gasket and RTV...it leaked.
.

That's why I used the specific PERMATEX RTV formulated to withstand diff gear oil. No leaks. Bone dry.

Permatex 81182 Gear Oil RTV Gasket Maker, 3 oz.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
The RTV seemed to set up VERY quickly. It was unlike any other RTV I have worked with. It "dragged' when we put a thin coat on both sides of the paper gasket. But I was able to get a quite even and uniform seal with it. Good stuff and dirt cheap. I could not dissolve even a fresh dollop of this RTV in the Liqui Moly 75W-140 diff oil.

Overnight free with Amazon Prime.
Contrary to popular belief, every unguent and potion does not have to have a BMW logo on it.

Take for instance my old clicking right half axle. The grease. Half of the OEM BMW grease had liquified over the years...and was sloshing around inside the boot. Gross.
I packed the new half shaft exclusively with Redline CV2 full synthetic cv grease. I loaded a 30cc syringe(no needle) with it and injected the grease deep in the bearings.

[Arith2]

That's why I used the specific PERMATEX RTV formulated to withstand diff gear oil. No leaks. Bone dry.

Permatex 81182 Gear Oil RTV Gasket Maker, 3 oz.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
The RTV seemed to set up VERY quickly. It was unlike any other RTV I have worked with. It "dragged' when we put a thin coat on both sides of the paper gasket. But I was able to get a quite even and uniform seal with it. Good stuff and dirt cheap. I could not dissolve even a fresh dollop of this RTV in the Liqui Moly 75W-140 diff oil.

Overnight free with Amazon Prime.
Contrary to popular belief, every unguent and potion does not have to have a BMW logo on it.

Take for instance my old clicking right half axle. The grease. Half of the OEM BMW grease had liquified over the years...and was sloshing around inside the boot. Gross.
I packed the new half shaft exclusively with Redline CV2 full synthetic cv grease. I loaded a 30cc syringe(no needle) with it and injected the grease deep in the bearings.

OE grease is Castrol CV grease. Porsche uses the same exact grease and there is no BMW logo. Liquimoly killed my bearings in my diff. Just an FYI.

[bigjae46]

OE grease is Castrol CV grease. Porsche uses the same exact grease and there is no BMW logo. Liquimoly killed my bearings in my diff. Just an FYI.

The bearings or the limited slip unit?


Sent from my iPhone using Tapatalk

[eacmen]

OE grease is Castrol CV grease. Porsche uses the same exact grease and there is no BMW logo. Liquimoly killed my bearings in my diff. Just an FYI.

Curious. How did you determine that the LM gear oil killed your bearings?

[Arith2]

Curious. How did you determine that the LM gear oil killed your bearings?

Bought the car, put around a thousand or so miles on it. Changed the fluid as preventative maintenance and it came out good. I filled it with Liquimoly and within 3000 miles it started getting this faint noise. Sounded like wind over the mirror basically. After another 5000 it was just a scraping and completely redid the rear in hopes it wasn't the diff. Nothing indicated it had ever been rebuilt because that paper gasket was quite stuck but not leaking. The pinion bearing was destroyed. I did fluid change somewhere in there and it came out grey. I checked 1000 miles later, and the new fluid was grey. I stopped using Liquimoly and looked into their products a bit deeper. Great marketing for sub par oil. My conclusion is it's the German Royal Purple basically. It lead to my few hundred hours of research on oil. I'll leave it at that as I'm not trying to turn this into an oil thread.
The diff was fine when I bought the car. It was driven 200 miles from where I bought it from. I didn't get around to changing the fluid for a month or so of owning the car so I know it wasn't failing before I bought it. The only factor the changed was the diff fluid. The car had 66k miles on it when I bought it. I rebuilt it after maybe 10k miles. The failure didn't just happen over night. It took a while. I rebuilt the diff at about 78k miles and all is good. I did a 1000 miles round trip with no issues afterwards. I used Motul with some FM. I'm on the fence on switching back to OE because I just landed 3 liters for free, but Motul as well as it can in a viscous clutch.

For the gasket on the diff, the best way to mate two metal surfaces with just RTV and is to spread a thin layer all over the mating surface and cover it completely. I learned that trick from an old Goldmeister Porsche tech. He rebuilds 993s while fixing Taycans all day. The man is good at what he does. BMW does not recommend using the paper gaskets anymore but mine held up for 15 years so it's whatever people prefer. If there's pitting, maybe use RTV and if the surface looks great, use paper. I literally just used the Permatex oil resistant black RTV and it's all good.

[Cubieman]

That's why I used the specific PERMATEX RTV formulated to withstand diff gear oil. No leaks. Bone dry.

Permatex 81182 Gear Oil RTV Gasket Maker, 3 oz.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
The RTV seemed to set up VERY quickly. It was unlike any other RTV I have worked with. It "dragged' when we put a thin coat on both sides of the paper gasket. But I was able to get a quite even and uniform seal with it. Good stuff and dirt cheap. I could not dissolve even a fresh dollop of this RTV in the Liqui Moly 75W-140 diff oil.

Overnight free with Amazon Prime.
Contrary to popular belief, every unguent and potion does not have to have a BMW logo on it.

Take for instance my old clicking right half axle. The grease. Half of the OEM BMW grease had liquified over the years...and was sloshing around inside the boot. Gross.
I packed the new half shaft exclusively with Redline CV2 full synthetic cv grease. I loaded a 30cc syringe(no needle) with it and injected the grease deep in the bearings.

I believe my half shaft innet boots to be leaking and possibly have the grease liquefied as well, is there a way to re-pack without having to separate the axel from the hub and diff?
Could one simply peel back the boots and then re-clamp?

[Arith2]

I believe my half shaft innet boots to be leaking and possibly have the grease liquefied as well, is there a way to re-pack without having to separate the axel from the hub and diff?
Could one simply peel back the boots and then re-clamp?

Just loosen it but I don't think you really need to fully remove them. Maybe loosen the diff to help slide the left axle out more. Maybe you can get the insides but the outsides probably won't be possible without unbolting something.

[BigDave]

Curious. How did you determine that the LM gear oil killed your bearings?

Me too. I reached out to ECS Tuning, Turner, and FCP Euro who all sell this diff gear oil. They all told me the same thing:

"Liqui Moly German products are among the worst in the world. Especially their diff fluid which we KNOW ruins ALL E46 LSD differentials in very short order. Realize we HATE BMW owners and this is why we continue to sell this gear oil."

What is the sarcasm emoji again??

I keep trying to destroy my 120,000 mile con rod bearings with Liqui Moly Synthoil Race Tech GT1 10W60 oil.
Plus a can of their Ceratec. Apparently I am failing because my oil reports keep coming back clean.