Rear End Refresh Questions

[Dbpiedade]

Hello!

So I've been searching the forum and reading about rear end refreshes, but have a couple of doubts that maybe are easy to clarify.

First thing is, generally the bushings to be refreshed are the RTAB's, the subframe mounts and the Diff cover and front bushings, correct? Or are there other "while you're in there" bushings or parts?

If so, my plan would be to go:

- CMP Solid Bushings for the Subframe mounts (I'm not lowered yet, but will be, so I'll just install these)
- OE Lemforder RTABS with Condor Limiter Kit
- Condor Poly Differential front and cover bushings.

My second question is regarding the Poly diff bushings. I know the consensus is to just replace the cover, but I've just (very) recently changed the differential oil with new BMW oil, which is expensive as hell, so not very keen in having to replace it all again. Plus, the cover is also quite a bit more expensive then the Condor bushings. Is this a big no-no or is the outcome just a bit more diff whine? It's mostly a weekend car so if that's all, I think it would be allright.

Also, would replacing the cover bushings with Condor poly and the front bushing with OEM (this one is available separately from BMW, right?) be a better solution?

Thank you very much for the help!

[bmwfnatic]

I am not the biggest fan of the OE RTAB, since you have to take the preload (actually prevent any from occurring) into account when torquing down the bracket that goes into the pocket. Not insanely difficult, but just a bit annoying.

I did it once and they ended up not lasting very long.

I am also not convinced for the use of limiters or a poly bush in the RTAB position, since limiting the range of motion doesn’t seem like the best idea to me.

Since you are willing to spend the money on CMP subframe mounts, spend the extra cash and get their sealed bearing RTAB as well (or the one from SDW). It gives the RTA a full range of motion, will do a better job of retaining toe while driving, and will outlast the OE rubber stuff.

As for the differential bushes, anything but stock will introduce sounds coming from the differential into the cabin from my experience, wether or not that bothers you is entirely up to you Another possibility is using the E36 M3 bushing, they fit into the E46 M3 cover, but there is some unsettled debate about wether they are the same hardness or not.

Lastly, a good ‘while you are in there’ would be to replace the inner upper control arm rubber bush, they tend to last pretty long but while you have it all apart, you might as well. Use OE rubber for that position. It will have to be torqued at ride height, which isn’t possible, so measure or guesstimate.

[Thoglan]

100% agree with above, I am going through a similar process at the moment. I opted for:
OEM pretty much everywhere except
E36 diff cover bushings - supposedly softer than the stock E46 m3 bushings but it's probably negligible and it's either that, go aftermarket (significant increase in NVH), or pay several hundred for an entire new diff cover which seems excessive.
CMP monoball RTABS and subframe bushings.

Only thing to note, if you don't have adjustable camber arms, putting the CMP bushings in without lowering might give you too much positive camber that you can't correct with the stock adjustment.

[RockyMtnM3]

"while you're in there" led me to also replace the upper and lower outer control arm bushings (attached for reference: 551). I also reused my diff cover, haven't experienced any issues or increase in diff whine.

[Dbpiedade]

I am not the biggest fan of the OE RTAB, since you have to take the preload (actually prevent any from occurring) into account when torquing down the bracket that goes into the pocket. Not insanely difficult, but just a bit annoying.

I did it once and they ended up not lasting very long.

I am also not convinced for the use of limiters or a poly bush in the RTAB position, since limiting the range of motion doesn’t seem like the best idea to me.

Since you are willing to spend the money on CMP subframe mounts, spend the extra cash and get their sealed bearing RTAB as well (or the one from SDW). It gives the RTA a full range of motion, will do a better job of retaining toe while driving, and will outlast the OE rubber stuff.

As for the differential bushes, anything but stock will introduce sounds coming from the differential into the cabin from my experience, wether or not that bothers you is entirely up to you Another possibility is using the E36 M3 bushing, they fit into the E46 M3 cover, but there is some unsettled debate about wether they are the same hardness or not.

Lastly, a good ‘while you are in there’ would be to replace the inner upper control arm rubber bush, they tend to last pretty long but while you have it all apart, you might as well. Use OE rubber for that position. It will have to be torqued at ride height, which isn’t possible, so measure or guesstimate.

Thank you for the very thorough awnser. I will look into the CMP RTABS then. It easily gets very expensive to replace all of these so may have to collect parts and replace when possible. I thought that it was settled that the E36 bushing was softer, but if it's a negligeable difference, it may be a better solution and can always replace with poly later on if I feel the need.

[Dbpiedade]

100% agree with above, I am going through a similar process at the moment. I opted for:
OEM pretty much everywhere except
E36 diff cover bushings - supposedly softer than the stock E46 m3 bushings but it's probably negligible and it's either that, go aftermarket (significant increase in NVH), or pay several hundred for an entire new diff cover which seems excessive.
CMP monoball RTABS and subframe bushings.

Only thing to note, if you don't have adjustable camber arms, putting the CMP bushings in without lowering might give you too much positive camber that you can't correct with the stock adjustment.

Thank you. I may just try and get a set of eibach springs when installing the CMP subframe bushings. Doesn't make sense to me buying something else and then having to replace when I do lower the car. As I said above, I may look into the E36 bushings, may be a good cost/benefit solution, as a new diff cover does sound excessive, specially having to replace the oil again (which seems to be liquid gold).

By the way, do you have the correct P/N for the E36 bushings at hand? Thank you again!

[Dbpiedade]

"while you're in there" led me to also replace the upper and lower outer control arm bushings (attached for reference: 551). I also reused my diff cover, haven't experienced any issues or increase in diff whine.

Did you use E36 bushings for the diff? I will look into these bushings you referenced too, thank you!

[jayjaya29]

E36 rear diff bushing part number is 33171134872

[Dbpiedade]

E36 rear diff bushing part number is 33171134872

Thank you!

[Ramps]

I did this 2 years ago, did the E36 rear diff bushings, CMP solid subframe bushings, OEM RTAB with limiters, OEM ball joints and front diff bushing, and ECS adjustable lower control arms. Rides super tight with no extra NVH.

[ejendow]

For those running solid subframe bushings, is your topside reinforced as well?

[Ramps]

For those running solid subframe bushings, is your topside reinforced as well?

I had turner plates welded on when I bought the car in 2010, I did a full inspection when I refreshed the rear end to make sure there were no cracks or rust. All clear. I plan on getting a brace from Pure-Tech for the top side this year.

[SQ13]

Fwiw, it appears that the later model year Euro E36 M3s (which made 321 HP) use the same bushing, according to realoem. So I imagine they should work fine in an E46 M3 diff?

[WestBankM4]

For those running solid subframe bushings, is your topside reinforced as well?

When I did my full suspension refresh front and rear, I ended up having Turner Plates welded in (if I could do it again, I'd choose a different plate manufacturer) and added the Vincebar Epoxy/Rivet version at the same time. Upon removal of my subframe (car had 108k miles at the time) there didn't appear to be any cracks, UNTIL they scraped all the gunk off and found two hairline cracks. Super minimal but they were present, I can honestly say this car was never driven harshly, yet there were cracks.

Do the bottom and top at the same time to save you troubles. I went with CMP Subframe and RTAB's bushings at the same time.