Given all the diff talk... help me out

[asultan]

https://w124performance.com/docs/mb/other/differentials.pdf

Ive seen this above link and referenced it for stuff in the past on my 1986 300E. Yes I know this is the 500E board but I hang here anyways...

So from what I've gathered in order to build a 210mm LSD for my car I need the diff out of a R129 300SL per bicylindrico on youtube, or one of the M104 W124's?

What about flanges? Bigger axles? Ratios? HELP!

 

[gsxr]

What year / model car are you working with, and what is the planned upgrade - limited slip? Different ratio? Etc.

If it's the 1986 300E, what engine upgrades are you planning to need the 210mm diff?

 

[asultan]

What year / model car are you working with, and what is the planned upgrade - limited slip? Different ratio? Etc.

If it's the 1986 300E, what engine upgrades are you planning to need the 210mm diff?

Turbo M103 on the way, just making it the last thing on the laundry list

 

[gsxr]

Turbo M103 on the way, just making it the last thing on the laundry list

OK, next question is what gears do you plan to install? If you can live with 2.65 that will be by far the easiest, swap everything from a late W124 with M104 (diff, axles, etc).

If you want a different ratio it may become quite a bit more challenging. If the transmission will remain 722.3 then the 2.65 ratio might be about perfect though.

 

[asultan]

OK, next question is what gears do you plan to install? If you can live with 2.65 that will be by far the easiest, swap everything from a late W124 with M104 (diff, axles, etc).

If you want a different ratio it may become quite a bit more challenging. If the transmission will remain 722.3 then the 2.65 ratio might be about perfect though.

Definitely wanted something in the range 3.07-3.64 range, My car also has the 717.430 gearbox… not sure if that really screw’s things up. I saw the aftermarket company kangaroos team makes a 210mm diff cover for the 6cyl subframe.

 

[gsxr]

Looks like the 717.430 has a 0.80 fifth gear, correct? In that case a 3.06 ratio might be about perfect, and should be 100% bolt-in from a 1991-1992 300CE (without ASR). Or, the 3.27 from a 1990 300CE. With lower power I'd lean towards the 3.27 and with higher power, the 3.06 ratio.

No need for an aftermarket 210mm diff cover for 6-cyl subframe, although with enough power, you might consider an upgrade to the V8 subframe. Kinda depends on the torque level expected from the M103-TT.

717.430 single mass flywheel
Gear ratios (5-speed)
5th (0.80) 2.45:1
4th (1.00) 3.06:1
3rd (1.38) 4.22:1
2nd (2.18) 6.67:1
1st (3.86) 11.81:1

717.430 single mass flywheel
Gear ratios (5-speed)
5th (0.80) 2.62:1
4th (1.00) 3.27:1
3rd (1.38) 4.51:1
2nd (2.18) 7.13:1
1st (3.86) 12.62:1

 

[asultan]

Looks like the 717.430 has a 0.80 fifth gear, correct? In that case a 3.06 ratio might be about perfect, and should be 100% bolt-in from a 1991-1992 300CE (without ASR). Or, the 3.27 from a 1990 300CE. With lower power I'd lean towards the 3.27 and with higher power, the 3.06 ratio.

No need for an aftermarket 210mm diff cover for 6-cyl subframe, although with enough power, you might consider an upgrade to the V8 subframe. Kinda depends on the torque level expected from the M103-TT.

717.430 single mass flywheel
Gear ratios (5-speed)
5th (0.80) 2.45:1
4th (1.00) 3.06:1
3rd (1.38) 4.22:1
2nd (2.18) 6.67:1
1st (3.86) 11.81:1

717.430 single mass flywheel
Gear ratios (5-speed)
5th (0.80) 2.62:1
4th (1.00) 3.27:1
3rd (1.38) 4.51:1
2nd (2.18) 7.13:1
1st (3.86) 12.62:1

You're saying that the 90 300CE as well as 91-92 should be equipped with the right diff cover is what i gather? What about axles? Axle Flanges?

 

[gsxr]

You're saying that the 90 300CE as well as 91-92 should be equipped with the right diff cover is what i gather? What about axles? Axle Flanges?

Correct, the 90-92 300CE share the same 6-cyl subframe and AFAIK it will bolt in to your 300E. You'll need the 300CE axles as well. The flanges will be part of the 300CE diff and are larger than your old ones.

The tricky part will be figuring out the driveshaft connection. I think the 300CE uses larger diameter flex discs. You can swap the input flange/yoke, just be extremely careful not to over-tighten the nut. Using larger driveshafts from a W124+M104 might be a better solution. You can't use the coupé driveshaft because it is shorter.

 

[asultan]

Correct, the 90-92 300CE share the same 6-cyl subframe and AFAIK it will bolt in to your 300E. You'll need the 300CE axles as well. The flanges will be part of the 300CE diff and are larger than your old ones.

The tricky part will be figuring out the driveshaft connection. I think the 300CE uses larger diameter flex discs. You can swap the input flange/yoke, just be extremely careful not to over-tighten the nut. Using larger driveshafts from a W124+M104 might be a better solution. You can't use the coupé driveshaft because it is shorter.

I think I may actually already have the thicker flex disc, last time I replaced both I found out that to my surprise factory manual w124's have a specific flex disc i assume to accommodate more driveline vibration? That was my assumption at least when the dealer told me its a different part... just found a 91 CE being parted out not over 100miles from me though

 

[gsxr]

EPC shows the same flex discs for both auto and manual trans in the 300E. The difference isn't thickness, it's diameter. Discs for higher-torque applications are larger diameter. I think the sizes are 80, 90, 100, and 110mm bolt circles. But I'm not sure which sizes are used on which chassis. See FSM job 41-050.

However, the EPC does show the front driveshaft is different between manual & auto... could be a length difference, in which case the late sedan shaft might not work after all. LA = auto, LM = manual.