subframe/diff re enforcement

[sinner88]

Anyone seen people reenforce the subframe with gussets or add a 2nd ear on the diff? i've heard of some kits out there but havent come across any good pics yet. any help would be great

[jlevie]

I've not seen anything to suggest that any reinforcement is needed on anything that remotely resembles a stock E30.

[sinner88]

i was talking to some guys at akg and valley motorwerks here in sacramento and they said there is someone doing it, they suggested it for me becuase of the way i drive my car,the rim and tire size and the hp i'm about to be putting down at the end of the build

[A.J.]

Severe duty subframe reinforcements:

http://www.s14.net/forums/showthread.php?t=47123

[sinner88]

Severe duty subframe reinforcements:

http://www.s14.net/forums/showthread.php?t=47123

Thanks....looks like a nice kit. Have you seen the kit where a second ear is mounted on the diff? I've heard that the diff can twist slightly under extreme acceleration,etc

[A.J.]

Second ear? Like on an e36 diff cover? I haven't seen one for the e30.

The kit on s14 beefs up the four points where the diff bolts to the subframe. The diff can't twist much since it's solidly mounted to the subframe. Twisting forces that don't get transmitted to the wheels get transmitted to the body via the subframe through the subrame bushings and diff mount bushing. Hard poly or solid aluminum bushings would reduce any movement of the subframe and diff under hard acceleration....an extra ear would distrubute any forces being transmitted to the diff mount bushings to two points instead of one, but I'm not sure it's necessary. Your tires will likely spin before the diff/subframe starts wiggling around too much.

[sinner88]

ya thats what i was thinking too. i only brought this up after talking to the owner of a bmw shop here in sacramento. so i'll re enforce the subframe but will most likely just skip the second ear. i guess its more of a z3 type of double ear. i'll keep doing some searching tho just out of curiosity

[rThor432]

Damn, I accidentally went back a page and deleted everything I had typed..

The stock subframe that I hot-rodded for my purple car came from an '85 5-speed 4-door eta. It was damaged. 3 of the 4 holes for the diff mount were elongated and one had a crack about 1.75" long running from it. One hole was fine, it looked like the others backed out over time and used that one as an axis. I the diff mount points with 1/8" plates and also reinforced the trailing arm mounting points.

As for the two ear diff info, keep searching. The info is around. Here's a hint-- try searching for info regarding an E36/7 or Z3. The stock Z3's and M cars had single ear diffs, but some of the M-car guys were getting whiney about diff bushings or breaking subframes in half so they decided to do something about it. I'd gladly share the info, but I will have to search through a bunch of unorganized links to find the info.

I'm considering installing an E36 M3 rear suspension in place of the trailing arm setup, that's one way to install a two ear diff.

[bmwmech1]

I just did a dual ear E36 cover swap on my build. It's easy to do, you have to relieve the E36 case on the inside to clear the reluctor ring and make a .300" spacer for the speed sensor to space it away to clear the ring and that's about it. Of course, you'll have to fab the mounts to mate it to the subframe, but if you're handy with a welder and can fab metal, it's very do-able. I made a whole new cross member out of 2"X2" .120 wall square DOM tubing, so I could tie in the rollcage also, but you could tie it into the OEM cross member, as well...

Garey

[sinner88]

I just did a dual ear E36 cover swap on my build. It's easy to do, you have to relieve the E36 case on the inside to clear the reluctor ring and make a .300" spacer for the speed sensor to space it away to clear the ring and that's about it. Of course, you'll have to fab the mounts to mate it to the subframe, but if you're handy with a welder and can fab metal, it's very do-able. I made a whole new cross member out of 2"X2" .120 wall square DOM tubing, so I could tie in the rollcage also, but you could tie it into the OEM cross member, as well...

Garey

Thanks a lot. sorry for the late response when i asked the question! i remember reading some stuff you posted about starting that project. i'll goo look at it now. i still havent fixed that with my car cuz i've been busy with some other mods i'm doing to my car. i have a bunch of pix just havent posted them yet.

[browntown]

I didn't reinforce the subframe or diff but I did put the rear sway reinforcements in the trunk floor and welded cross bars on the trailing arms and doubled the steel on the mounts for the sway links.