6CYL Swap "The Real Truth"

[hellrot332ti]

I had an open stock diff and it last about 2 years before it broke. Mine broke on the drag strip so depending on your driving styles the 4 banger diff. could last forever.

[aceyx]

Where was the fault point?

[hellrot332ti]

Originally Posted by aceyx

Where was the fault point?

Well i broke about 4 teeth off of the input shaft that meshes with the ring and pinion, coming from the driveshaft. It just wasnt made to handle the torque i guess..

[tctwnd]

is swapping the flanges difficult?

[jdehaan]

so if the stock TI diff could potentially last for quite a while, what are the advantages of going to an Mroadster diff, besides the eventuality that it will fail if given enough time and hard driving. What are the performance advantages? Also, how much should a quality, used Mroadster diff cost?

[J!m]

It will break, and typically at the worst time, regardless of driving style.

Ben Liaw broke his at a stop light. He wasn't racing, just trying to move when the light turned green. No warning either- no noise, nothing.

If you plan to always be walking distance from home (you should be walking, not driving in this case...) you are fine. Also invest in AAA for the tow you will need.

When (not if) it fails, there may likely be zero warning of the failure, and no logical reason for the failure. Obviously, racing (particularly drag racing) will speed-up the diff failure, but simple street driving will take its toll.

[Hawkster]

So will a diff out of an E36 M3 coupe fit? I've got one in the bed of my truck... so if it will... I might not sell it...

[stormos]

won't fit.

[jdehaan]

What about an M Roadster, or an E30 M3. Which one is best?

[cali-ti]

Originally Posted by jdehaan

What about an M Roadster, or an E30 M3. Which one is best?

i'm assuming you're talking about the diffs. believe the m-roadster/m-coupe are 3.23 and the e30 m3 is 4.10. there were m-coupe/roadster guys installing e30 3.73 LSDs into their cars even, but it really depends on what you're hoping to achieve, faster accel times or nice highway cruising rpms or what?

[racepad]

I recently purchased a complete rear end from a M Roadster and was led to believe that basically the whole thing was a bolt in into the ti. Ugh - no way. I was going to do the job myself but decided to farm it out to Turner Motorsport as I am in the midst of relocating. Here is what works and does not. The carrier will bolt up, the diff flange was 4 bolt and it mates with the drive shaft. Well that is about it. The brake lines come out at a different angle on the M3 brakes so custom lines had to be built and other lines from an E30 M3 used. The brackes on the carrier for the lines had to be removed and the old ones moved over to the new carrier. The Diff does not fit and some body work had to be completed. The old diff support removed and a new one fabricated and welded on to the body. The wheel base is now wider but that will create some wheel fitment issues for me (235x40x17 SSR Comps withYokohama AVS tires). May have to now have the rear fenders rolled. We stayed with the old sway bar as the roadster one required larger bushing mounts. This would have required cutting the stock ones off, fabricating new ones to fit the wider M roadster rear sway bar. When I get the car back in a few weeks I will share more.

[J!m]

Originally Posted by racepad

I recently purchased a complete rear end from a M Roadster and was led to believe that basically the whole thing was a bolt in into the ti. Ugh - no way. I was going to do the job myself but decided to farm it out to Turner Motorsport as I am in the midst of relocating. Here is what works and does not. The carrier will bolt up, the diff flange was 4 bolt and it mates with the drive shaft. Well that is about it. The brake lines come out at a different angle on the M3 brakes so custom lines had to be built and other lines from an E30 M3 used. The brackes on the carrier for the lines had to be removed and the old ones moved over to the new carrier. The Diff does not fit and some body work had to be completed. The old diff support removed and a new one fabricated and welded on to the body. The wheel base is now wider but that will create some wheel fitment issues for me (235x40x17 SSR Comps withYokohama AVS tires). May have to now have the rear fenders rolled. We stayed with the old sway bar as the roadster one required larger bushing mounts. This would have required cutting the stock ones off, fabricating new ones to fit the wider M roadster rear sway bar. When I get the car back in a few weeks I will share more.

WOW. What did you do? you said you had the entire thing, but obviously you did not. I have to chime in as I have said (and done myself) this is easier than swapping the diff. You have dug yourself a deep hole there. I hope you have not cut anything, because the ENTIRE assembly DOES bolt right in (look under my car anytime). If you mix-n-match parts, you have problems, as I have said several times over now.

• The diff fits the stock ti mounting locations; no cutting needed
• The sway bar simply needs new bushings and bushing mounts; no cutting needed
• I have fit 275-40/17's on M3 8.5 rear wheels with a 1/4 lip roll, 245-17s fit perfect, 265-17s (on my car now) fit with slight roll. Your SSR offset may be incorrect for the car.
• Brake lines need to be modified; however the stock lines can be cut and re-flared to fit as I did, and the mounts do need to be moved; however the holes are pre-drilled for them on the M roadster sub-frame
• Parking brake cable will not fit on the roadster locations, so large zip-ties are used to hold them to the tailing arms