75 2002 Sleeper - M20B32, ITB, LSD

[justinevert]

Trudat, but lot of us don't have the skilz like you do!

Justin

[tinkwithanr]

Ha, thanks. But you never know until you try.

[Eau_Rouge]

Excellent build!

What are you planning on running up front, e30 front subframe?

Here's a link to a very similar build to yours. This individual used an e36ti front and rear subframes/suspension etc.

http://www.bmw2002faq.com/component/...opic/t,338579/

Very cool project, keep up the good work!

[tinkwithanr]

Thanks! For the front I'm still using the stock '02 subframe, but it's been heavily modified with wider/stronger motor mounts as well as an e21 steering rack. If you look back a few pages you'll see some of the modifications.

Also, I don't think your link worked, but from the sounds of it I'm pretty sure I know what thread your talking about. Funny thing is the 318ti E36 has the same rear subframe assembly as the e30 (compared to the completely different setup on all other e36's), so I've actually been using his thread for some tips lol. Definitely a good read!

[tinkwithanr]

The next order of business was to fabricate the new mounts for the rear subframe. After taking some measurements I made a quick sketch of what I needed to turn and got to work.

The Sketch:

Shown in the sketch is the 'bottom plug'. This is what will hold the mounting studs for the two forward mounts on the rear subframe. The bottom plugs will be welded to a piece of 1.5"-0.120 wall DOM tubing, which will then allow me to tie the mounts into the roll cage and unibody very easily. Also, by leaving the top of the tubing open, the studs will be able to be removed/replaced if necessary. This could come in handy if the threads get stripped or rusty over time.

The material I used for the bottom plugs was 416 Stainless, which has good machinability while being very corrosion and wear-resistant. Starting with 1.5" bar stock, a couple hours later I had these:

And here are all the parts of the subframe mount in an exploded view. From left to right: DOM Tubing, Mounting Stud, Bottom Plug, Subframe Bushing, Lower bracing Plate.

This is how the plugs slide into the DOM tubing. The chamfered edge is to help the weld penetrate better, as well as give the filler material somewhere to go.

And here is how the plug fits onto the subframe bushing. The aluminum insert in the bushing fits up into the plug, and when bolted in the aluminum is tight up against the counter bore in the plug.

Everything put together to double check before welding:

Next it was time to press in the mounting studs. For this I used the stock e30 studs pulled from the parts car. The studs themselves have a knurled shoulder right under the head. This is press fit into the plug to hold the stud in place.

The stud loose in the plug, before being pressed in:

After being pressed into the plugs:

After welding the plugs into the tubes:

The two assemblies installed onto the subframe. Here you can also see the jig I made up to help position the subframe under the car:

Finally, with the subframe roughly in position, you can see the DOM tubing sticking up into the cabin area. I'll need to trim the top of the tube down to be even with the floor, I left it extra long since I didn't know how much I would need.

Hoping to get the subframe squared up and welded in place along with the diff mounts tomorrow. Then it's on to the trunk floor!

[Meintii]

WOW. Those look awesome man! Its always cool to see an original idea comes to life. Your making me jealous...

[M3M3]

yes, some great work you are doing!

however, think you need to delete "sleeper" from your title...no way this car is goiing to be innocuous! :-)

[tinkwithanr]

Thanks guys!

With the front mounts made up it was time to get the subframe square with the car and figure out how high I wanted to tuck it up into the body. Luckily I was able to talk my friend into helping me during the measuring and finessing the assembly into position. After about an hour of tweaking and adjusting I was happy with where it was sitting, and I tacked the front mounts in place. This then allowed me to figure out the correct placement of the rear cross member, which would hold the rear mounts for the diff cover.

Here's the front subframe mounts tacked in place. The bolts are a little long, but I don't think it will hurt anything. Worst case scenario I'll just trim them down a bit:

Here you can see the area cleaned up and ready for the new material to be welded in:

Next we cut and measured the cross member piece along with the extra side panel reinforcements. Here are both welded in place:

Close up of the driver side. The plate that the cross member is welded to is to help reinforce the inner wheel well. The weld-thru primer made my welds a bit crappier than I would have liked, but they will definitely hold.

With the cross member in we put the subframe back in place so we could measure for the diff ear mounts.

Front face of the mounts cut out:

Due to the way the bushings on the diff cover are, the ear mounts need to have a small, circular offset to them. So I TIG'd some washers onto the back of the ear mounts. This allows the inner portion of the bushing to be held rigid to the mount without rubbing on the outer portion of bushing and diff cover.

I then gusseted the ear mounts to add some rigidity and welded them in place on the cross member under the car. This let me remove the jack and see the subframe held in place on it's own for the first time.

Nother Diff Shot:

Here you can kind of see the gussets I added to the diff mounts. Essentially the cross section is a 'C' shape, except at the bottom where there isn't a worry of it flexing (it's lower than the bolt hole). I'm also going to add a gusset above where the ears sit once I take the subframe back out.

Last but not least here is a side view of the diff. You can see how it sits up against the body of the trunk floor. The cover has a clearance of about 1" between the top of it and the front of the cross member, which will be plenty of room.

Next up will be framing out the trunk floor and fit the fuel cell into postion. Then I can repair/brace the inner wheel wells and measure for my rear coilovers.

[AceAndrew]

You're having WAY too much fun. As always love seeing the updates.

[tinkwithanr]

You're having WAY too much fun.

Quoted for when you first fire up the triple webers.

[tinkwithanr]

Not the most glamorous of updates, but an update none the less.

Keeping with the theme of working on her backside, I decided to test fit my rear bumper to see how it would look with the flares. Still a bit abstract at this point, but I like where it's heading.

Next up was to finish removing the last pieces of the old rusted trunk floor. Here you can see the rear panel of the trunk, and the upper and lower lips of the trunk floor that are left:

These were attached with a crap-ton of spot welds, and some seam sealer. So first thing first I drilled out all the welds:

Then carefully pealed away the seam sealer and viola! no more trunk floor:

With that taken care of it was time to start patching the rear panel. It had a few area's that were very pitted, as well as the old 'diving board' bumper mounting holes. I forgot to take pictures of all the steps of cutting and patching, but long story short about 1000 tack welds later this is what she looked like:

Note the truly centered exhaust cutout (I still need to cutout the indented section of metal). This is different from both early and late cars, as the early ones had the cutout over on the right hand side and the later cars had a slightly offset 'center-ish' exit. A true center exit was something I always liked, so I figured why not.

Did I mention there were a lot of tack welds...

Then I moved on to the driver side rear quarter panel. While not as bad as the passenger side, it was still pitted enough to require a full replacement.

The Bad:

The good:

Once I finish grinding the welds smooth I'll start fabing the trunk floor and fuel cell mounts. Then it's on to the front of the car!

[Colin]

Very nice! Those are some of the best looking welds I've seen on this forum!

[Tommy]

Nice job with the rear axle. Sleeper appearance will be pretty much lost with the flares.

Tommy

[tinkwithanr]

Very nice! Those are some of the best looking welds I've seen on this forum!

Ha, thanks. But there's a reason there aren't any close ups of them... lol

Nice job with the rear axle. Sleeper appearance will be pretty much lost with the flares.

Tommy

True, but as long as the intercooler isn't showing I doubt anyone will expect the cute little box to put down 400hp to the wheels.

[tinkwithanr]

Very nice! Those are some of the best looking welds I've seen on this forum!

Ha, thanks. But there's a reason there aren't any close ups of them... lol

Nice job with the rear axle. Sleeper appearance will be pretty much lost with the flares.

Tommy

True, but as long as the intercooler isn't showing I doubt anyone will expect the cute little box to put down 400hp to the wheels.