Subframe risers and offset diff bushings? Help...

[haaken675]

Hey everyone. This part is really confusing me. I am planning on ordering all new subframe bushings for my build. There are obviously several manufacturers, but the part that is throwing me off is if I want the 12mm riser bushings or spacers, and if so do I then wan/need an offset diff bushing as well? I have tried looking this up, but I have not been able to come up with a clear answer.

If it helps, I am doing a 24v turbo swap build, so I WILL be putting down some power. This will be a striped out street/track car (mostly track).

Thanks in advance everyone.

[glnr13]

you want the bushings and spacers with the subframe risers, keeps the driveshaft 'straight'.

[PA_Welder]

you have to use spacers under the 4 mounts from the diff to the subframe but that keeps the diff in the same place so the driveshaft keeps the same alignment and you will use a standard diff bushing.

[haaken675]

There are raised bushings. Do they essentially do the same thing? I messaged Garagistic, and their response was I then needed an offset diff bushing as well...

I don't know why his part throws me off so much.

[glnr13]

i think what Welder meant was that by using a raised subframe bushing AND the diff bushing/spacers you keep the driveshaft at the same angle as if you had all standard stuff.

[haaken675]

maybe its because I have ha a long day, but i'm really not getting this one...So, if I lower my car, say with coilovers, I will incur negative camber as a result. From my understanding, there are 12mm risers that will correct that? Here are examples from both condor and garagistic where they offer risers, but there are no offset diff mounts, raised bushings, etc.:

https://www.condorspeedshop.com/collections/e30-parts/products/copy-of-combo-ps-delete-m20-motor-trans-mounts-offset-cabs-12mm-subframe-riser-bushings-trailing-arm-bushings-diferential-mount?variant=274799272

https://store.garagistic.com/E30-polyurethane-bushings/BMW-E30-complete-polyurethane-suspension-kit

Are you saying that I will need something in addition to these? Are they not packaged correctly, or am I loopy from sales calls all day...To me, part of the problem is I can't seem to find a good article that actually explains everything. Couple that with every manufacturer seemingly describing things (and what they claim you need) differently, I am obviously a bit confused.

Thanks again for everyone sticking it out to help.

[haaken675]

Ok, so I made a drink and I think my brain started working...

So, if I am thinking correctly, if I was to get raised subframe bushings, then I would need an offset diff bushing. But if I do the 12mm diff bushings, that essentially corrects the angle on it's own, or do I need taller bushings as well? I just don't see anything like this in any of the packages, so that just throws me off.

[glnr13]

raised subframe bushings = buy 12mm diff bushings or stud kit, buy offset diff bushing

that's what's recommended by them.

[haaken675]

cool. Makes sense now. Again, the biggest part that throws me off is that everyone offering the 12mm spacers doesn't appear to then offer an offset diff bushing or raised subframe bushings...

[glnr13]

I did a little digging in the interwebz and there are conflicting theories on the offset diff bushing. some say it's needed, some say it adds tension on the rear u joints, some say the spacers do nothing if you don't put the offset bushing, some say without the offset bushing it leads to faster wear on the regular bushing... I dunno the answer. I have the raised subframe bushings with the 12mm spacers on the diff but without the offset diff bushing and everything seems cool.

[LowR3V'in]

you don't need it.
i've done this mod. you just put spacers on the diff to keep everything in the same spot.
think about it. That slotted diff bushing idk wtf its actually for.

probably to drop it down if you didn't use spacers.
but then why not use spacers?

[Northern]

+1^

Rear subframe/diff assembly has 3 pickups on the unibody: The two subframe bushings and diff mount. When you space two of them up(subframe risers), you need to do the third as well.

Two different, mutually exclusive ways to accomplish that. 1: 12mm diff spacers + longer bolts/studs, or 2: 12mm offset diff mount.

The diff spacers keep the diff in the right position, so driveshaft angle doesn't change, and there's no risk of your driveshaft hitting your subframe or gas tank heat shield.

Diff mount seems to be an older way of doing it, which works fine for some.

[HerbE30]

I have a spare set of spacers and extended bolts for the diff, if you need them.
This is the route I went.