525It Turbo LS Swap

[flynfrog]

Going to a single piece drive shaft. I didn't want to drop the money for a custom drive shaft to hook up to a 188 diff that will die soon. Id planned this diff swap from the beginning and the 8.8 has pretty much anything you want for it.

[flynfrog]

Got some more done.

After consulting ye old scrap pile I got front Brackets done. These were a bitch to tack weld. Also note if you haven't welded in 3 years an off handed vertical weld with no room for the torch while you run the pedal with your elbow probably isnt the best one to start with.
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Looks like I could fit a 4inch driveshaft with no cutting but a 3 gives much more room.
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[flynfrog]

Got one and a half rear brackets done today.
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UPS man brought some goodies
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Axles should be here tomorrow. Hoping to wrap up fab by friday and clean the bench to build CVs. Need to get the last bracket done and put the subframe in the car and measure for a drive shaft.

[moroza]

I once looked into a one-piece driveshaft and was told (by a slightly questionable shop) that for the RPM and length parameters of an E34, a conventional steel tube would need to be 5" diameter to have a reasonable critical speed. Given that some of the larger 2-piece E34/E32 shafts approach 3 inches in OD... unless I'm missing something, this ain't gonna work.

[flynfrog]

You are missing things.
here is a chart with critical speeds
https://www.markwilliams.com/servicebull/sb0049.pdf even at stock length there are options that will work that are not 5".

I don't have BMW transmission I think I am roughly 6-8 inches longer so even shorter driveshaft than stock. I am also going to a taller gear ratio so shouldn't be spinning the shaft as fast anymore anyway.

[flynfrog]

Last bracket welded up
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Everything back together
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Camber and toe tabs welded on. These are a little tough as most things on the subframe don't line up with each other. I went with the the subframe mounts so they will at least be squareish to the car.
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just made it with the welding gas. Hoping I have enough to mod the exhaust.
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[flynfrog]

The axles look like they will work.
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[flynfrog]

Got it into the car today. no clearance issues
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Hammered center bearing number 2
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Cleaned up the shop and bench
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[flynfrog]

Just in time to build axles.

New vs 540 axle
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Greased up the CVs
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Hell of a time to run out of gloves
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All done compared to a 525 axle
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[flynfrog]

Got the drive shaft ordered should be done thursday.


Preparing to do battle. If you have never used carbide burrs on steel they make tons of tiny needles basically. They will poke you through your clothes get in your shoes gloves ect. They are the worst. Wear your PPE
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Getting on with it
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Satans glitter
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Removing some of the non believer parts of the sub frame.
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All assembled and ready to go into the car.
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[moroza]

Thanks for documenting this. I'm not well-versed in domestics; I wonder if there is a manual locker available for that diff?

[flynfrog]

Subframe is back in and waiting for the driveshaft and a few odds an ends for the CVs
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[flynfrog]

Thanks for documenting this. I'm not well-versed in domestics; I wonder if there is a manual locker available for that diff?

Do you mean one you can turn on and off? if so yes they do exist.
https://eastcoastgearsupply.com/i-13...pline-all.html

The cool thing with the 8.8 you can get spools torsens lsd open pretty much any diff you can think of you can get for it. The same with gear ratios.

[flynfrog]

On a side note does anyone know where this wire goes once its in the car. it looks like it enters under the rear seat I was hoping it goes into the engine compartment first before the dash so I don't have to pull the cluster again. speedo wire.PNG

[moroza]

I don't believe that wire ever enters the engine compartment. Comes from the diff, through a hole behind the battery, across the rear seat, forward along the port-side rocker, up behind the dead pedal, and eventually into the cluster. The cluster sends its own speed signal to the DME; not sure how it's routed, but at least on a manual car it's totally unnecessary, and clipping it removes the top speed limiter (at least on my M6x car).

[flynfrog]

I dont have the wheel in the diff anymore so I am going to have the GM computer give it the signal. What do you mean its unnecessary? Is it not how speedo gets its signal?

[moroza]

The speed signal to the DME is totally unneccessary, at least on a manual-trans car. The signal to the cluster is, of course, for the speedometer.

[flynfrog]

Got the drive shaft in today
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[flynfrog]

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Got the CVs torqued down and the boots banded up.
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Gave her the old spin test. No bad noises other than my idle map.

[moroza]

How long before some 30-130 runs?

[flynfrog]

Hoping to get everything bolted up this weekend but then there is closing down the street in Mexico

[flynfrog]

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Pulled the dash to make the speedo great again. You want the red and brown wire in this bundle. Then hook it to pin 50 in the green connector if you have an 99-07 truck ecu

I had to reprogram it to work. The default is 4k per mile pulse. My car was a 7085 pulse per mile with a stock tire and 8 pulse wheel. I checked it to the GPS and it seem pretty close
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I took the picture a little late but the speed moved

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Getting some rear alignment on. One gripe with the adjusters they are pretty much impossible to get to the toe adjusters. The camber wasn't much better. maybe having it on a real rack would help but the toe adjust is right on top of the dogbone nut.

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back on the ground.

- - - Updated - - -

Did some easy driving around to check for rubbing. A little noise from the diff on turning. But I think it's the clutches breaking in.

Did a pull my tune is still pig rich but pegged 15 psi and held it.

[flynfrog]

Well Shitte
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Soulution throw more steel at it

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Went out and did some testing of the boost pig. I think he needs a better mount and a more positive retention system

[moroza]

I didn't want to come off as a nitpicky knowitall raining on your parade (more than I do anyway), but that rear brace did not look very strong to me from the start. Your new one doesn't look much better, and honestly the original mount on the rear cover is sub-optimal as well. Holding the differential's torque is easier from a radius away from the point of rotation, while the stock boss is quite central. Apparently this is a thing:


And I'd pursue a similar solution, except take it a step further. Two, or better yet, one plate that fits around the 8.8 rear mount and bolts to the rear cover bolts, welded to the side-mounting tubes at their front, and another plate welded to the side tubes' rears, joined to the front plate with a few welded side braces, and if possible, tapered so that it joins the front plate directly at the bottom.

Perhaps ditch the side tubes and replace them with multiple large (ideally square) nuts, welded to the plates? Since they're taking through-bolts, your choices need not be limited to M14 or whatever the OE bolts are.

[flynfrog]

If it breaks again I would do it differently but Ill see if this holds up. Likely do a bar between the factory mounts and keep the tabs and plate similar to what they are now. Sorta like this one