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Z3 / E30 Differential Reinforcement Fab Work

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  • Z3 / E30 Differential Reinforcement Fab Work

    As some of you know we have a full service race fab and repair shop here at Vorshlag. In this thread I will show the rear chassis reinforcement and custom differential mounting we did on a customers Z3. This same work can be done to a BMW e30 chassis, which shares the same rear subframe and differential mounting issues.

    Tony J's 1999 BMW MZ3 Coupe



    This car has the same single ear diff mount that rips it self out of the trunk floor on many Z3 and E30 models. Tony's Z3M has an Active Autowerks supercharged S52, so it sees more torque than most! With cracked trunk floor (see above) it was in dire need of some Vorshlag surgery and upgrades.



    We started by a thorough detailing of the car on Monday. We always do this, as it shows everything clean up front and then we can wrap/cover any body and interior areas we need to work near without grinding dirt into those surfaces. Once it was spotless outside, inside and under the hood, on our guys put the car up on the lift to make some measurements and verify parts we needed to order. We have another car having an entire trunk floor replaced that got worked on Tuesday, but late that afternoon our guys got back to the Z3M and removed the rear interior panels/carpets, covered the inside rear windows with paper and made a plastic barrier to the interior, then covered the body areas with towels, then covered all of that with welding blankets (during welding - not shown).



    The tar paper insulation in the trunk area we are repairing had to be removed and then we weighed it all(1.2 lbs). These "uncovered" areas were cleaned up in preparation for surgery.





    Measurements were taken with the stock diff housing in place, then measured from the stock single-ear mount cover back to where the E36 dual ear mount Rogue Engineering cover would be. The placement of the new cross beam was marked on the chassis, the diff center section was removed and the and the cut lines were begun. The car has been up and down on the lift a dozen times by now.



    Then out came the cutting tools - a variety of air & electric, metal and carbide cutting blades were used to slice out the 3" wide channel where the 3x3" x 11 gauge square steel tube will go.



    That's where we left it today - all still on schedule, even with the new maintenance items added. Should be wrapped up Friday night. We have all of the steel tubing now, more welding gas for the TIG and MIG welders will be here in the morning, and then its time to burn metal. I picked up some fresh seam sealer, proper metal etching primer, and managed to find a pretty darn close color match for some spot work (top side of trunk area - which will all still BE under the rear interior carpet).



    More soon,
    Last edited by Fair!; 11-05-2015, 09:45 AM.
    Terry Fair - www.vorshlag.com
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

  • #2
    Re: CHASSIS WORK projects @ Vorshlag

    Progress plus New Things Learned

    Today we ran into some unforeseen issues and delays, stemming from interference with the Rogue E36 style dual ear mount diff cover when bolted onto the Z3 housing. Once again I let someone tell me something that I knew couldn't be correct, trusted the advice of the vendor of a product, then found out that they were wrong and that I should have been super skeptical. It was something we had seen before on an E30 project, where we modified the E36 cover to clear the reluctor wheel of the E30 diff, and then spaced out the speed sensor - so I shouldn't have been surprised. I knew better... and don't rely on the advice of others.



    So here are the facts: When using an E30 or Z3 diff with an E36 rear diff cover you have to swap on the E36 speedometer reluctor wheel (to the smaller diameter E36 unit) and E36 speed sensor itself onto the Z3 differential and new cover. We had been told by Rogue that this wasn't an interference with their cover, but of course its just like any other E36 rear cover - it needs the matching E36 parts or you have to cut a groove into the rear cover and space the speed sensor back by the same amount.



    These E36-specific parts don't cost much money ($6 for the wheel) but can add delays if you are trying to find one in a hurry. The E36 reluctor wheel isn't stocked in the USA and takes 7-10 days to come in from Germany. Luckily we have E36 differential housings on hand and robbed an E36 M3 diff of its reluctor wheel and speed sensor. Just added some hours we hadn't planned on, but now we know - and so do all of you (if you didn't already know). Figured I'd share the pictures here so you guys wouldn't re-learn this mistake on your own if you ever did a dual ear mount swap on an E30 or Z3.



    The Z3 differential carrier was removed from the housing and the E36 reluctor ring ring was pressed onto the carrier. Then that was all put back together in the Z3 housing and the Rogue rear cover was RTV'd, installed, and torqued in the proper sequence. Now we can move onto the trunk rework and new dual mounting supports.



    The actual trunk floor work is moving along once again, with the 3x3" cross beam cut to fit the floor opening, between the frame rails. It is nesting down inside the channel we cut out and sitting on top of the edge of an inner lower structure where the swaybar mounts. The actual swaybar mounts will be replaced with a better, dual bolted, poly swaybar mount (shown in the parts picture at the bottom of this post).



    Now that the main cross beam is fitted in place we can finish up the reinforcement spreader plates that will weld up against, then mock-up the Z3 differential with the Rogue cover, measure and set the pinion angle of the diff housing, and cut and weld on the diff mounts that go to the dual ear mount.



    New front tires are mounted and balanced, our wheel stud parts are ready to go on, the new Lemforder tie rod and lock washer is here, and new poly dual-bolt swaybar bushing/mounts are ready to go on.

    More soon,
    Terry Fair - www.vorshlag.com
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

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    • #3
      Re: CHASSIS WORK projects @ Vorshlag

      Getting closer....









      More soon...
      Terry Fair - www.vorshlag.com
      2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
      EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

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      • #4
        Re: CHASSIS WORK projects @ Vorshlag

        Done? Final pics? Picked up?


        Costas
        cars and such...

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        • #5
          Re: CHASSIS WORK projects @ Vorshlag

          Final update!

          My last update was from Friday at 5 pm. Ryan stayed on and worked until 3:30 am on the final welding, painting, and assembly. He was the Iron Man! I left at 8 pm but came back at 11:30 pm and worked with him until the wee hours. Yes, we under-bid this job by a good amount, but Tony paid what we quoted and got a damned fine installation, if I say so my damn self. :stickoutt



          Here its about 7:30 pm and you can see the main cross beam is in and starting to be welded to the frame rails. Spreader plates are already welded onto the sides of the frame rails.



          These "T" shaped plates tie the tops of the frame rails to the tops of the cross beam. Everything TIG welded, of course. You can see the bottom trunk sheet metal being stitch welded to the cross beam on the top right pic.



          Here you can see the 2-bolt swaybar bracket mounting plates being fabricated and then being welded to the cross beam. These were triangulated with more plate, as shown. The differential cover ear mounting tubes (down and angled) are full TIG welded at this point, too.



          Several welding steps are not shown here, because it was midnight by this point and we were trying to finish before day break. The full length of the cross beam was stitch welded to the trunk floor, front and back. This welded seam was then wire wheel cleaned, wiped down with lacquer thinner, and a bead of seam sealer was applied to the full perimeter of the cross tube plus all of the plate steel welded to the chassis. Once this dried we cleaned all of the bare steel again, applied tape and paper to everything we didn't want to paint, then sprayed everything with zinc enriched primer. Both the trunk floor area above and the underside metal was primed, then as one side was drying the other side was being sprayed with color.



          The top tide was covered in a nearly matching green (Detroit Diesel engine block paint!) and the bottom was sprayed with semi-gloss black, with two color coats on each. Now we were loopy from the paint fumes and from lack of sleep...



          Once the paint dried and the paper was removed we started on re-assembly of the underside of the subframe and differential. By this point its about 1 am and we're still going strong. Caffeine is a wonderful drug!



          Once the diff was reinstalled and the pinion angle verified, the swaybar with the new 2-bolt polyurethane mounts was greased and installed. The OEM exhaust heat shields went on next and were trimmed slightly to fit around the new steel tubes and swaybar mounts. By now its about 2 am.



          The rear trunk interior panels were in a dozen pieces, which we vacuumed and then stared at for a minute. The technician who removed it all was at home and asleep. Oh well, Ryan and I figured out this jig saw puzzle and got all of the factory pieces back in place, and even added a gaggle of OEM fasteners that were missing - we keep all of the BMW trim panel clips and such in stock. The only piece of green sheet metal showing now was visible when we got the car. The stock interior panels pieces fit snug and flat over the new cross beam, and nothing looked modified once the panels were all in place. We had cleaned up the shop and finished by 3:30 am and I was at home and sound asleep by 4, and I presume Ryan was in snoozeville at his place around the same time. Wiped out.



          The next morning I was up at 6 am (sleep is for the weak!) to go to a huge Cars & Coffee show here in Dallas in our 2011 Mustang (which was especially eventful after a woman crashed a new Camaro into two Corvettes - in the parking lot! She "had a seizure" or something. See after-crash pics on the Feb 2012 C&C gallery on my FB page). We were there for a few hours and left at 9:30 am (and I found out that Tony stopped by C&C after his flight landed and saw us leave). Headed to the shop and double-checked all of the nuts and bolts that we touched in the early morning hours, cleaned up the exhaust and took these final pics.



          Ready for pick-up! Tony and his lady friends arrived at about 10:30 am and picked up his Z3, then he drove it 5+ hours home - with the trunk floor repaired and reinforced, front suspension repaired and re-aligned, new front tires, wheel studs installed, and the car fully detailed.

          Our solution to the "Z3 trunk floor fix" is pretty different than the other ones out there (I just looked at some of those today) and I feel its stronger (using tubing and not just plate steel mounts for the diff), more secure (fully TIG welded), and also fixes the swaybar bracket problem at the same time.

          As I mentioned at the beginning of this post, we underbid this job by sizable margin, but after doing this first Z3 we could replicate this work with 30 hours of fabrication (we burned more than that), now that we've done one and know the proper steps. So at $75/hour (our current fabrication rate, which is subject to change if we get busier) figure about $2250 in labor and another $250 in parts, so you'd be looking at $2500 for Vorshlag to do this to your car. The parts included are the reluctor ring, sensor, poly bushings, new 188mm E36 diff dual ear cover, all of the tubing and plate steel, and new Redline diff fluid.

          That's without the Rogue diff cover used here, which would be another $450 above those quoted numbers ($580 retail - the OEM E36 dual ear mount's cost). Optionally we could replace all of the side axle seals and dust covers in the diff carrier for another $95 (the diff carrier has to be blown apart and put back together anyway).

          No, we will not be selling this in any "kit" form, as all of the steel plate and the cross beam was hand-built to fit the car during installation and not easily replicated, nor was the installation even remotely "DIY" - you need a fab shop to do this, who could presumably make all of this on their own. This installation also added about 16 pounds to the rear of the car when completed - not much considering the added strength it brings to this chassis (the cross beam alone weighed in at 12 pounds, before it was trimmed to shape).



          We have had a number of inquiries about this Z3 and other chassis fabrication work, and are now booked through March 15th at the moment. If you would like to talk to us about this type of work to your E30, Z3, or even E36 / E46 (see above; we've done that work as well, but it is a lot easier than the E30/Z3), just give us a call at 972-422-7170 or e-mail us at sales@vorshlag.com.

          Lessons learned: Any time you use an E36 diff cover on an E30/Z3 differential you will need the E36 speedometer reluctor ring ($6) + speed sensor (10+ days from Germany), and we would pre-order matching body color paint 1-2 weeks in advance, as well as the swaybar mounts and any seals that could be potentially bad.

          Thanks for watching,
          Last edited by Fair!; 02-06-2012, 07:38 PM.
          Terry Fair - www.vorshlag.com
          2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
          EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

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          • #6
            Re: CHASSIS WORK projects @ Vorshlag

            If you don’t mind me asking, where do you get (part #, etc.) The E36 speedometer reluctor wheel and speed sensor, I am attempting something similar with an e30 diff in my '71' 2002

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