DeadPool DEFEATED! -- 540i6 Front Mount Turbo Build

[MrExecutiveBoss]

20190609_160920_HDR.jpg

So i broke the front diff mount. Im having it repaired and reinforced by a trusted welder, and im switching to a solid aluminium bushing for the front mount. A bunch of people have told me it would be better to get a whole new subframe because its gonna break again but my welder said that sounds to him like people who dont know how to weld. Additionally he and I were curious if there is a way to add a secondary mount on the other side of the diff so that i have two front mounts distributing the stress.

[JimLev]

Welding should hold, you could probably add another front support by welding an extension angle iron to the case and then fab up some type of mount to the subframe.
I cracked mine years ago, I fixed it and it's been fine.

[MrExecutiveBoss]

Would just welding it to the case be enough? My guy was talking about tapping into the case with bolts. But he wasnt sure

[JimLev]

You did a good job of busting that mount....side stepping the clutch at 5K??
I don't think it's a good idea to tap into the case. I'd look into welding a piece of angle iron to it.

[tptrsn]

Looking at that pic now that you have it out of the car, it looks to me like the Powerflex bushings were pressing apart on the subframe (front to rear) even harder than I thought. I suppose that would be good for really keeping the diff solidly in place, but maybe not great for keeping the subframe in one piece for the longest possible length of time. Or maybe because they probably kept slop from occurring at all, they could have done a great job of lengthening the working life of the mount structure, who knows...

Anyway, if you end up trying to add a mount to the other side Nick, you're in mostly uncharted territory. Schitzo may have an idea about it, since he has grafted some ford 8.8 "punkins" into some E39 subframes. But my impression is that most guys who have done something to the aluminum subrames to reinforce them, have just repaired the mount, and then boxed it in. That seems to do the job from what I recall.

Chris, did you do something like that?

But as for adding structure to the M5 diff case, I think they are cast iron (?) which is tricky to weld to. It can be done, but usually it requires at least *some* pre and post heating, and use of a high nickel filler rod. If your welder is very smart and experienced, he'll know how to do it.

And just thinking out loud here, but it seems to me that the front mount structure is actually put in tension when you let off the gas abruptly, or wheel hop type action. If you can successfully keep the wheels spinning, or hooked up putting down power, the front of the diff is pushing up, keeping that mount structure in compression.

[MrExecutiveBoss]

Lol not side stepping the clutch Jim. Dont think ive ever done that at all. No just romping the bejesus out of it.

[MrExecutiveBoss]

I went ahead and forwarded what you said to my welder Thad. Gonna see what he says

[JimLev]

When I broke my cast iron vise I bought a few sticks of nickel welding rod and then broke off the flux coating so I had just the nickel rod left. I used my torch to heat it up to about 400F and then TIG'ed it back together.
It's still fine.

[tptrsn]

That's cool Jim! Do you remember the number of those rods you used, or what they were intended for? They were stick welding rods, correct?

Just throwing it out there for general conversation, I used regular old ER70-S2 filler when I welded my mild steel modifications to the truck manifolds I'm currently running on the LRS. Basically I wanted to see what all of the fuss was about with regard to welding onto cast iron. The manifolds do seem to be working fine so far, but I really had to keep heat on them for a while after welding, or they would make a lot of ugly noises like they were going to crack apart immediately as they cooled...

Passenger side patches.jpg

Driver's side welded up.jpg

[philly98540]

Anyway, if you end up trying to add a mount to the other side Nick, you're in mostly uncharted territory. Schitzo may have an idea about it, since he has grafted some ford 8.8 "punkins" into some E39 subframes. But my impression is that most guys who have done something to the aluminum subrames to reinforce them, have just repaired the mount, and then boxed it in. That seems to do the job from what I recall.

Chris, did you do something like that?

My stock mount is still holding up great. I just looked at it the other week. No cracks as yet. When they do break, everyone just adds some extra pieces of aluminum plate to box it in like Thad mentioned above. Its all that needed and it holds up excellent once that is done. No reports of these breaking even with 600+ Hp set ups. Do some searching to see what the extra pieces look like. Its a simple job for a decent TiG welder.

But as for adding structure to the M5 diff case, I think they are cast iron (?) which is tricky to weld to. It can be done, but usually it requires at least *some* pre and post heating, and use of a high nickel filler rod. If your welder is very smart and experienced, he'll know how to do it.

I agree with Thad here. I'm sure a good welder could add the extra support with some good welding skills, but its an unknown risk that is not needed. A lot more work involved that just fixing the single mount.

And just thinking out loud here, but it seems to me that the front mount structure is actually put in tension when you let off the gas abruptly, or wheel hop type action. If you can successfully keep the wheels spinning, or hooked up putting down power, the front of the diff is pushing up, keeping that mount structure in compression.

YESSSS! The front mount is being pushed up when your on the gas. I think most break from nasty wheel hop and doing harsh downshifts with an abrupt clutch release. Those events put major downward tension force on the front mount. The upward forces from strong acceleration likely adds to the wear and tear on the welds, but I don't think they are the main cause of the breaks, but likely a contributor. I don't get wheel hop, so maybe that is why mine is still good. Or maybe mine was welded on a Tuesday and the guy did a better job than a Friday welded one...

[JimLev]

That's cool Jim! Do you remember the number of those rods you used, or what they were intended for? They were stick welding rods, correct?

Yes, just electric stick rods. I'll see if I can find the numbers.
The local weld supply shop had rolls of nickel wire ($$$$) but I only needed a little so they suggested a stick rod.
I don't remember if I used my MAP or acetylene torch to heat it up red hot. Did the heated cool down too.
Thad, I think it might have been you that told me to use nickel on cast.

[tptrsn]

Thad, I think it might have been you that told me to use nickel on cast.

Could be Jim. I have known about this for a while, but you know me, I don't get much of a kick out of doing things the way that is probably the "right way". Lol

Chris, thanks for the info! I think that will give Nick a good handle on the situation, and then he can decide what he wants to do from there. Pretty sure he would like to give your record a run at some point, and now that he has the good clutch in the car, he might be able to take a decent crack at it once he has the diff mount fixed up.

The icing on the cake would be to run a clutch switch for launch control and flat shift so that he could run the entire length of the quarter mile in boost. I ran that setup on my MS3X Neon with a Precision billet 6265 on it, and it was insanely fun at about 30psi and fat slicks on the front. Lol.. Now that I'm thinking about it, that car is kicking around Philly somewhere I think!

[JimLev]

Found it. It was a 4 pack of rods. I only used 4" of one rod.

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[tptrsn]

That's awesome Jim, thanks!!

[computiNATEor]

YESSSS! The front mount is being pushed up when your on the gas. I think most break from nasty wheel hop and doing harsh downshifts with an abrupt clutch release. Those events put major downward tension force on the front mount. The upward forces from strong acceleration likely adds to the wear and tear on the welds, but I don't think they are the main cause of the breaks, but likely a contributor. I don't get wheel hop, so maybe that is why mine is still good. Or maybe mine was welded on a Tuesday and the guy did a better job than a Friday welded one...

I get wicked wheel hop on my M5, with the stock LSD, stock 275/35/18 Michelin Pilot Super Sports/Pilot Sport 4S, and Dinan by JRZ rear suspension. The rear bushings and control arms were replaced at 105,000 miles. I'm at 164k now.

[JimLev]

I got the same wheel hop problem with the 2.81 pegleg and with the M5 diff.
If I want to launch hard I can't have the RPM any higher than 1600-1700.

[tptrsn]

What diff bushing and subframe bushing setup are you guys running that get wheel hop, and what setup are you running with no wheel hop Chris?

[Laminar]

Could be Jim. I have known about this for a while, but you know me, I don't get much of a kick out of doing things the way that is probably the "right way". Lol

Chris, thanks for the info! I think that will give Nick a good handle on the situation, and then he can decide what he wants to do from there. Pretty sure he would like to give your record a run at some point, and now that he has the good clutch in the car, he might be able to take a decent crack at it once he has the diff mount fixed up.

The icing on the cake would be to run a clutch switch for launch control and flat shift so that he could run the entire length of the quarter mile in boost.

For a clutch switch I just used a motorcycle rear brake switch I already had lying around.

https://www.ebay.com/itm/Motorcycle-...kAAOSwHVdckaNe

The threaded portion lets you adjust the moment of engagement and the spring lets you push the pedal beyond engagement without damaging the switch.

What diff bushing and subframe bushing setup are you guys running that get wheel hop, and what setup are you running with no wheel hop Chris?

There's a really interesting thread on eng-tips about IRS wheel hop.

https://www.eng-tips.com/viewthread.cfm?qid=434286

Some tips on ways to mitigate, but a lot of discussion about how OEMs have kind of given up on mechanically stopping wheel hop and just use traction control to quell it.

[computiNATEor]

What diff bushing and subframe bushing setup are you guys running that get wheel hop, and what setup are you running with no wheel hop Chris?

I’m on fully stock and original equipment diff and subframe bushings. Probably going to get a solid front diff bushing, reinforce the front mount, and replace the rears with soft poly.

On the subframe, I may try polyurethane stock bushing reinforcements/inserts. They take up the open air space in the stock bushings. The subframe bushings aren't known for failing except on wagons, really. I’ve had four E39 sedans with one reaching far past 225,000 miles on factory subframe bushings.

There's a really interesting thread on eng-tips about IRS wheel hop.

https://www.eng-tips.com/viewthread.cfm?qid=434286

Some tips on ways to mitigate, but a lot of discussion about how OEMs have kind of given up on mechanically stopping wheel hop and just use traction control to quell it.

Good read, thanks.

I should probably also say that I was on stock and original equipment engine and trans mounts. Both will be new as my S62 refresh wraps up. I should prob update that thread. Short block reassembly begins tomorrow!!

[MrExecutiveBoss]

Heres what i had done with the diff mount

[JimLev]

Yup, that should work OK.
Thad, you giving it your blessing?

[tptrsn]

For a clutch switch I just used a motorcycle rear brake switch I already had lying around.

https://www.ebay.com/itm/Motorcycle-...kAAOSwHVdckaNe

The threaded portion lets you adjust the moment of engagement and the spring lets you push the pedal beyond engagement without damaging the switch.



There's a really interesting thread on eng-tips about IRS wheel hop.

https://www.eng-tips.com/viewthread.cfm?qid=434286

Some tips on ways to mitigate, but a lot of discussion about how OEMs have kind of given up on mechanically stopping wheel hop and just use traction control to quell it.

That is great info dude!! I'm still trying to figure out my best approach to an overtravel switch of some sort for my 2-step activation on my handbrake in the current car, and I will give that motorcycle switch a good look.

As far as the wheel hop stuff, also interesting. I have done the different axle thickness setup on Nick's car, and for me it was usually pretty smooth. He has had some issues with it obviously, but the clutch was acting goofy for quite a while from the sounds of it, and that may have contributed to some of the trouble.

Yup, that should work OK.
Thad, you giving it your blessing?

I do think it will work fine Jim, yes. I feel for the guy who did the work, because he would probably have liked to have better access to boxing in the front mount more completely, and also for better angles to make stuff more aesthetically pleasing... But I think the approach he took looks like it will certainly strengthen the mount by a massive amount to keep it from breaking in a similar fashion again. I'm impressed with the way he went about it.

[philly98540]

Agreed. New approach on this repair looks pretty strong.

[tptrsn]

Took the LRS to the drag strip the other night with a new pair of $41 head gaskets (for the pair) in the iron block 4.8L. Apparently the $137 turbos (for each) are doing some work:

Milan Time Slip 8-19-19.jpg

Some dude took some nice pics of the ridiculous drift car at the dragstrip nonsense:

I slapped on some 12 year old 235width drag radials, so I was doing soft burnouts as the internetz say drag radials prefer:
Milan Soft DR Burnout.jpg

And this was the car "launching," which really means when the lights came down I would just mash the throttle and go. Not even loading against the brakes:
Milan Soft Launch.jpg

Later in the evening I did load it against the brakes and e-brake, and cut a 1.76 60ft, but fuel level was below 1/2 tank, and it fuel starved before the 1/8th mile. It should have been real close to a 9 second pass. So I guess a 9 is the goal for later in the year.

[JimLev]

WOW, 114 in the 1/8! Nice going Thad.
Would be nice to see what the LRS could do in the 1/4.