Cracked subframe-Should I go with OEM subframe bushings?

[alpinem3///]

I have cracked my subframe and will be replacing it. I was debating if I should stick with OEM bushings or try the Urethane Bimmerworld Purple bushings.

Could I run the urethane bushings for the subframe and oem for the diff? Would this be ok.

My concern with the Urethane bushings is the noise, can anyone speak from experience or recommend what has worked well with their car. The car is a street car, which is more geared towards quarter mile racing then auto x.

[SiGmA]

IMO, go with poly all around. Purple or black Powerflex, or better, AKG.

[Mad Dog 20/20]

Depends.

DIY? go w/ poly for the ez install
No DIY? Go OE.

I have a custom-built diff, with delrin diff bushings and PF sub bush. I do feel/hear some slight diff vibe on decel.

[MKovac]

I have purple powerflex in my subframe and AKG Polys's in my Diff.

I DD the car and personally I love the feel compared to OE bushings in the diff.

I used to run purple powerflex bushings in my subframe with oe diff bushings and after I snapped my subframe like you I switched over to the AKG poly's and couldn't be happier. The slop that I had in the rear end immediately went away and the car was alot tighter when shifting, launching and even noticable during cornering. I would highly reccomend this settup, I wouldn't have it any other way. FYI for suspension I run koni yellows and H&R sports so I'm used to a bumpy ride.

Either way I think you gain alot in handling from a small sacrifice in comfort when you put the harder bushings in your rear end. whoa. I should throw in a no homo for that.......

[SiGmA]

Q, where did you crack your subframe?

[DavidsM3]

oem is safer for the subframe hands down.

[SiGmA]

Please define "safer" with a detailed explanation please

[DavidsM3]

Please define "safer" with a detailed explanation please

The harder subframe bushings cause more stress on the mounting points over time then oem bushings, and they are not really meant for a street cars for this reason. The softer bushings allow more flex in the rubber i.e easier on the subframe, and the harder bushings do not which causes more stress on the mounting points of the subframe.

[SiGmA]

So are people having re-enforced chassis failures with poly??

[DavidsM3]

So are people having re-enforced chassis failures with poly??

depends on who does the work, and alot of the times poorly done reinforcing after a subframe is ripped can be a hard fix. Now a properly reinforced subframe before a rip can hold together really well, but the poly's still add more stress to the mounting points then the oem. The oem bushings take more of the beating. If people payed more attention to things like bushings when pushing these cars beyond stock power less issues would happen.

[SiGmA]

Okay, how about with stock chassis reinforcement, such as with M3's? Any issues? I guess I need to read the track section more

[DavidsM3]

Okay, how about with stock chassis reinforcement, such as with M3's? Any issues? I guess I need to read the track section more

Anything can happen. The m3's it happens less often, but it happens to the m3's as well. I had afew friends back in the days who used to beat on/drive them like they stole them. They messed up subframes on e36 m3's, and e46 m3's just doing retarded things on the street. Just like you hear of people breaking diff bolts on stock cars never mind FI'd 1's right?

[SiGmA]

Fair enough. I've never read of E36 M3 chassis issues, thus my confusion. I'll butt out now.

OP, I still stand by poly bushings. Or aluminum

[ArBrnSnpr]

I have poly sub-frame bushings, OEM diff bushings (kicking myself in the ass for not going with AKG for the diff while the subframe was out). If you do with powerflex subframe bushings make sure and do the 330 bolt/thicker washer upgrade as powerflex washers can cup and creat space for the subframe to move. Or get the Bimmerworld kit and dont look back. I would recommend reinforcing the subframe, sway bar mounting tabs, and RTAB pockets while they're accessable though.

[GGray]

Non M E36 chassis will pull mounting points epecially on a track, even harsh streeet use or spirited driving. The E36 non M kit is the same thing BMW put on the E36M3 pickup points.

I DD my street/track car with somewhat not smooth roads no big deal HUGE improvement in how the car feels. On track its night and day the rear of the car with all the rubber stock bushings realy moves around with the Poly its planted and very predictable. As long as you don't drve like an ASS HAT on the street your fine. Track/street cars can run all poly in the rear. If a street only car run the poly street bushings on the subframe, stock diff bushings, and the upgraded RTAB's with limiters.

I currently have 550f 650rear springs with no rubber suspension bushings. I tried solid diff mounts WAY to buzzy for a car that see's street use. Pulled them back out. Once its a track/play toy I will put the diff bushings back in.

Basically same for the E46 chassis. I have one in the air doing the reinforcement kit now that is a track/street car. Preventitive maintance since its driven agresssivly on street and track.

[alpinem3///]

I was leaning towards stock bushings but I might do the poly in the rear and stock diff bushings as you suggested. have you had a chance to drive a car that has a set of fresh oem rear subframe bushings to base your comparisons off of?

Also how do you go about reinforcing the subframe on the e36 m3. There is already plates do you just weld over areas that were not welded from the factory?

[GGray]

Yes. Ive had a few E36M3's and I had to put new subframe bushing in my wifes old 325i.

Unfortunatly I've had subframes in E36's out too many times I can do it alone in under two hours.

They still feel like butter compared to the poly stuff on the subframe. Honestly it makes a huge change in how the car feels. I'll never put stockers in again.

The M3 already has the reinforced subframe mounts. if they rip/tear you have to weld them and be creative with some non available reinforcement.

BUT... The area on the E36M3 that does rip straight the heck out is the pocket for the RTAB. If you have it apart and know a welder buddy I would strongly recomend the pocket reinforcment kits, like Bimmerworld sells. One of my E36M3's had them cracked when I got the car. Typically if a street car they pull out from yahoo's at tire stores with impact guns doing the alignments. They are only tack welded in.. BMW fixed the problem on the E46 which then made, on non M cars, the main subframe mounting points pull apart.

The rubber RTAB's with limiters also make a nice improvement the limiters work well and preserve the ride NVH much like leaving the stock diff bushings in.

For soem real buzz try putting in solid tranny mounts... Holy cow!!! you'll think your driving a truck...

I fogot to mention if you are drag racing, per in the first post, stop doing hard clutch drops... Reinforce the new subframe diff mounts too. You have to make the reinforcements yourself I don't know anyone who sells them... Pretty easy to make.

[alpinem3///]

Good advice I think I am going with the powerflex bushings.

[ArBrnSnpr]

The sway bar mounts, and the subframe can be reinforced with scrap metal pieces cut to fit. The RTAB pockets have kits available. I suppose you could just go over the welds, but if you're already welding in the are why not buy the kit too...?

[SiGmA]

I hope this doesn't happen to me. Ugh. I have a spare subframe tho, and now I have access to a TIG, so I suppose I'll mod up a subframe and get it ready for when my yet-to-be-installed subframe fails, lol.

[HafaAdaiM3]

Do Powerflex, I ran a set of their hardened urethane race versions but had a failure on one bushing. Of course, the rest of my suspension comprises of mostly solid aluminum so I would suspect the weakest link the hardened powerflex bushings. Anyway, I replaced it, while it was out, I also installed Bimmerworld Solid Diff bushings and replaced my Diff Bolt.

You should do the latter of my approach because you'll need to remove it anyway. It was a PITA. I've done it twice.

PS. I also had my sway bar reinforced along with the subframe. Not sure who makes them, but they'll need to be welded on. Check Bimmerworld, they sell them.

http://store.bimmerworld.com/e36-rea...-kit-p541.aspx

http://store.bimmerworld.com/e36-rea...-kit-p985.aspx

I also did the front as well,

http://store.bimmerworld.com/e36e46-...-kit-p540.aspx

Those are really cheap modifications that will hold your car steady. My M3 is a 95 so I didn't have these from the factory but I've heard that the later 98-99 M3's came with the rear reinforcements already welded by BMW stock. Correct me if I'm wrong.

[SiGmA]

HafaAdaiM3 - Most 95's have the rear chassis reinforcements. Weird yours did not.

[bennyfizzle]

All M3 chassis had reinforcement plates, I've worked on a 1/94 car that had them.

[alpinem3///]

Is 500-550rwhp going to create problems with poly bushings. Also I live in SF and the roads are complete shit. I am thinking that I might go stock subframe bushings just based on the beating my car will take because of the roads. It worries me that Mkovac ripped his subframe on the same set up I was considering.

[macelius]

Yes this is a resurrection, It was the only relevant thread I could find.

Has anyone else seen this crack? I have my subframe out for AKG sway bar reinforcements and Revshift bushings. The bar mounts started cracking after a season with a Turner rear bar in, the original bushings were still good, showing only a minor surface crack here and there. Was cleaning up the bubbling paint and rust spots with a wire-wheel and noticed some hairline cracks just starting to form around the ends of the ear welds. Some paint peeling around the diff ear welds as well that could point to fatigue there. Glad I caught it in time to put a few more beads on before this happenned: http://www.m3forum.net/m3forum/showp...7&postcount=38. I would suggest anyone that has their subframe out check for these.

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