Fitting 124 300DT 2.65 diff gears in W123 diff case?
Fitting 124 300DT 2.65 diff gears in W123 diff case?
I had a 2.65 diff from a W124 turbodiesel laying around and took it apart since I wanted to get longer gearing for my W123 that has a 3.46 diff right now. I have both diffs apart and I instantly ran into 2 issues which are that the pinion physically is too big for the 123 case but only a little bit and the bigger issue that the lower pinion bearing hole seems to be 76mm in the 123 case and 82mm in the 124 case.
I have the older style 123 diff that has the 6 bolts on both sides. Does anyone know if the newer 123 case that doesn't have these bolts and should remind the newer style diffs and has more space inside and what size is the lower pinion bearing?
My old W123 diff pinion lower bearing size is about 36x76mm and W124 2.65 pinion bearing is 42x82mm. It also doesn't seem to be possible to fit the smaller bearing from the 3.46 pinion to the 2.65 because the shaft is bigger on the 2.65.
I looked up both bearings and the website selling them say both fit on a W123, which must mean some W123 models had the bigger lower pinion bearing.
I think a 3.07 differential ratio with a 5 speed gearbox would be the best but the 5 speed is rare even in Europe and the original 3.07 diff is also very rare and expensive to ship here.
If I can combine the W124 parts with the W123, I'd only be looking at a few hundred in bearings and seals at the worst. I also looked at installing a bmw 6 speed into the car and all parts could be bought but the price would easily be over 1000€. I'd rather just get a W210 with an OM606 at that point.
Please recommend any guide or place where to get this information. If you have the newer style diff apart, please check the bearing size. I looked at a restoration video about the newer diff and it's very hard to tell if the bearing is the smaller or bigger one. The only reason I don't check myself is that I only have the old differentials.
I will post images later of the items.
(08-09-2023, 12:37 AM)Echo575 I had a 2.65 diff from a W124 turbodiesel laying around and took it apart since I wanted to get longer gearing for my W123 that has a 3.46 diff right now. I have both diffs apart and I instantly ran into 2 issues which are that the pinion physically is too big for the 123 case but only a little bit and the bigger issue that the lower pinion bearing hole seems to be 76mm in the 123 case and 82mm in the 124 case.
I have the older style 123 diff that has the 6 bolts on both sides. Does anyone know if the newer 123 case that doesn't have these bolts and should remind the newer style diffs and has more space inside and what size is the lower pinion bearing?
My old W123 diff pinion lower bearing size is about 36x76mm and W124 2.65 pinion bearing is 42x82mm. It also doesn't seem to be possible to fit the smaller bearing from the 3.46 pinion to the 2.65 because the shaft is bigger on the 2.65.
I looked up both bearings and the website selling them say both fit on a W123, which must mean some W123 models had the bigger lower pinion bearing.
I think a 3.07 differential ratio with a 5 speed gearbox would be the best but the 5 speed is rare even in Europe and the original 3.07 diff is also very rare and expensive to ship here.
If I can combine the W124 parts with the W123, I'd only be looking at a few hundred in bearings and seals at the worst. I also looked at installing a bmw 6 speed into the car and all parts could be bought but the price would easily be over 1000€. I'd rather just get a W210 with an OM606 at that point.
Please recommend any guide or place where to get this information. If you have the newer style diff apart, please check the bearing size. I looked at a restoration video about the newer diff and it's very hard to tell if the bearing is the smaller or bigger one. The only reason I don't check myself is that I only have the old differentials.
I will post images later of the items.
(08-09-2023, 12:37 AM)Echo575 I had a 2.65 diff from a W124 turbodiesel laying around and took it apart since I wanted to get longer gearing for my W123 that has a 3.46 diff right now. I have both diffs apart and I instantly ran into 2 issues which are that the pinion physically is too big for the 123 case but only a little bit and the bigger issue that the lower pinion bearing hole seems to be 76mm in the 123 case and 82mm in the 124 case.
I have the older style 123 diff that has the 6 bolts on both sides. Does anyone know if the newer 123 case that doesn't have these bolts and should remind the newer style diffs and has more space inside and what size is the lower pinion bearing?
My old W123 diff pinion lower bearing size is about 36x76mm and W124 2.65 pinion bearing is 42x82mm. It also doesn't seem to be possible to fit the smaller bearing from the 3.46 pinion to the 2.65 because the shaft is bigger on the 2.65.
I looked up both bearings and the website selling them say both fit on a W123, which must mean some W123 models had the bigger lower pinion bearing.
I think a 3.07 differential ratio with a 5 speed gearbox would be the best but the 5 speed is rare even in Europe and the original 3.07 diff is also very rare and expensive to ship here.
If I can combine the W124 parts with the W123, I'd only be looking at a few hundred in bearings and seals at the worst. I also looked at installing a bmw 6 speed into the car and all parts could be bought but the price would easily be over 1000€. I'd rather just get a W210 with an OM606 at that point.
Please recommend any guide or place where to get this information. If you have the newer style diff apart, please check the bearing size. I looked at a restoration video about the newer diff and it's very hard to tell if the bearing is the smaller or bigger one. The only reason I don't check myself is that I only have the old differentials.
I will post images later of the items.
(08-09-2023, 03:42 AM)Alec300SDI am very aware that this diff was not available in a W123.(08-09-2023, 12:37 AM)Echo575 I had a 2.65 diff from a W124 turbodiesel laying around and took it apart since I wanted to get longer gearing for my W123 that has a 3.46 diff right now. I have both diffs apart and I instantly ran into 2 issues which are that the pinion physically is too big for the 123 case but only a little bit and the bigger issue that the lower pinion bearing hole seems to be 76mm in the 123 case and 82mm in the 124 case.
I have the older style 123 diff that has the 6 bolts on both sides. Does anyone know if the newer 123 case that doesn't have these bolts and should remind the newer style diffs and has more space inside and what size is the lower pinion bearing?
My old W123 diff pinion lower bearing size is about 36x76mm and W124 2.65 pinion bearing is 42x82mm. It also doesn't seem to be possible to fit the smaller bearing from the 3.46 pinion to the 2.65 because the shaft is bigger on the 2.65.
I looked up both bearings and the website selling them say both fit on a W123, which must mean some W123 models had the bigger lower pinion bearing.
I think a 3.07 differential ratio with a 5 speed gearbox would be the best but the 5 speed is rare even in Europe and the original 3.07 diff is also very rare and expensive to ship here.
If I can combine the W124 parts with the W123, I'd only be looking at a few hundred in bearings and seals at the worst. I also looked at installing a bmw 6 speed into the car and all parts could be bought but the price would easily be over 1000€. I'd rather just get a W210 with an OM606 at that point.
Please recommend any guide or place where to get this information. If you have the newer style diff apart, please check the bearing size. I looked at a restoration video about the newer diff and it's very hard to tell if the bearing is the smaller or bigger one. The only reason I don't check myself is that I only have the old differentials.
I will post images later of the items.
AKAIK the 2.65 ratio differentials were not available as a stock option for the W123 series.
I used this site in my search for upgrade options: https://mbturbo.com/gear-ratios/
In your case, the easiest plug and play differential swap would be a W123 or W116 3.07 1.1 liter (185mm wide housing) differential.
This differential has the right width, bolt pattern, and yoke.
No modifications required. You will have a reduction in acceleration compared to your current setup.
The following US cars had them:
(W123) 1981-1985, 300TD, OM617.952, 3.07, 1.1 Liter
(W123) 1982-1985, 300DT, OM617.952, 3.07, 1.1 Liter
(W123) 1982–1985, 300CD, OM617.952, 3.07, 1.1 Liter
(W116) 1978–1980, 300SD, OM617.950, 3.07, 1.1 Liter
(W126) 1981-1984, 300 SD, OM617.951 3.07, 1.1 Liter
There is also the quite rare (plug and play with no modifictions required) 2.88 1.1 liter (185mm) differential found on the following cars:
(W123) 1985, 300TD, OM617.952, 2.88, 1.1 Liter
(W123) 1985, 300D, OM617.952, 2.88, 1.1 Liter
(W123) 1985, 300CD, OM617.952, 2.88, 1.1 Liter
(W126) 1985, 300 SD, OM617.951 3.0L I5, 2.88, 1.1 Liter (California from 10.1984 in California: 2.88, 1.1 Liter
If you want a 2.65 (or lower) ratio, you will have to make modifications.
You will have poor acceleration compared to a 3.07 ratio differential.
The ones that have the right bolt pattern are off gassers and have a 1.3 liter capacity (210mm wide).
The yoke would need to be changed to the smaller diesel yoke, and the half shafts would need to be shortened as well.
The following cars had either the 2.65, 3.06 or 3.07 1.3 liter (210mm width) differentials:
(R107) 1973-1980, 450 SL/SLC, M117, 2.65 / 3.06, 1.3 Liter
(W116) 1973–1980, 450SEL, M117, 2.65 / 3.06 / 3.07, 1.3 Liter
(W116) 1975–1980, 450SEL 6.9, M100, 2.65 LSD, 1.3 Liter
My 1978 300SD (W116) came stock with a 3.07 1.1 liter (185mm) differential.
Before I bought the car in 2014, the prior owner had swapped in a 2.47 1.3 liter (210mm) differential with the yoke change and half shaft change.
Low engine revs at highway speeds, but quite poor acceleration with that setup.
The engine developed a rod knock so it is non-operational for now, saving for an engine rebuild and a front suspension update.
In the meantime, the rear suspension has been fully redone including a differential upgrade.
I splurged with a Wavetrac differential professionally installed in a (R107) 3.06 1.3 liter (210mm) differential.
(08-09-2023, 03:42 AM)Alec300SDI am very aware that this diff was not available in a W123.(08-09-2023, 12:37 AM)Echo575 I had a 2.65 diff from a W124 turbodiesel laying around and took it apart since I wanted to get longer gearing for my W123 that has a 3.46 diff right now. I have both diffs apart and I instantly ran into 2 issues which are that the pinion physically is too big for the 123 case but only a little bit and the bigger issue that the lower pinion bearing hole seems to be 76mm in the 123 case and 82mm in the 124 case.
I have the older style 123 diff that has the 6 bolts on both sides. Does anyone know if the newer 123 case that doesn't have these bolts and should remind the newer style diffs and has more space inside and what size is the lower pinion bearing?
My old W123 diff pinion lower bearing size is about 36x76mm and W124 2.65 pinion bearing is 42x82mm. It also doesn't seem to be possible to fit the smaller bearing from the 3.46 pinion to the 2.65 because the shaft is bigger on the 2.65.
I looked up both bearings and the website selling them say both fit on a W123, which must mean some W123 models had the bigger lower pinion bearing.
I think a 3.07 differential ratio with a 5 speed gearbox would be the best but the 5 speed is rare even in Europe and the original 3.07 diff is also very rare and expensive to ship here.
If I can combine the W124 parts with the W123, I'd only be looking at a few hundred in bearings and seals at the worst. I also looked at installing a bmw 6 speed into the car and all parts could be bought but the price would easily be over 1000€. I'd rather just get a W210 with an OM606 at that point.
Please recommend any guide or place where to get this information. If you have the newer style diff apart, please check the bearing size. I looked at a restoration video about the newer diff and it's very hard to tell if the bearing is the smaller or bigger one. The only reason I don't check myself is that I only have the old differentials.
I will post images later of the items.
AKAIK the 2.65 ratio differentials were not available as a stock option for the W123 series.
I used this site in my search for upgrade options: https://mbturbo.com/gear-ratios/
In your case, the easiest plug and play differential swap would be a W123 or W116 3.07 1.1 liter (185mm wide housing) differential.
This differential has the right width, bolt pattern, and yoke.
No modifications required. You will have a reduction in acceleration compared to your current setup.
The following US cars had them:
(W123) 1981-1985, 300TD, OM617.952, 3.07, 1.1 Liter
(W123) 1982-1985, 300DT, OM617.952, 3.07, 1.1 Liter
(W123) 1982–1985, 300CD, OM617.952, 3.07, 1.1 Liter
(W116) 1978–1980, 300SD, OM617.950, 3.07, 1.1 Liter
(W126) 1981-1984, 300 SD, OM617.951 3.07, 1.1 Liter
There is also the quite rare (plug and play with no modifictions required) 2.88 1.1 liter (185mm) differential found on the following cars:
(W123) 1985, 300TD, OM617.952, 2.88, 1.1 Liter
(W123) 1985, 300D, OM617.952, 2.88, 1.1 Liter
(W123) 1985, 300CD, OM617.952, 2.88, 1.1 Liter
(W126) 1985, 300 SD, OM617.951 3.0L I5, 2.88, 1.1 Liter (California from 10.1984 in California: 2.88, 1.1 Liter
If you want a 2.65 (or lower) ratio, you will have to make modifications.
You will have poor acceleration compared to a 3.07 ratio differential.
The ones that have the right bolt pattern are off gassers and have a 1.3 liter capacity (210mm wide).
The yoke would need to be changed to the smaller diesel yoke, and the half shafts would need to be shortened as well.
The following cars had either the 2.65, 3.06 or 3.07 1.3 liter (210mm width) differentials:
(R107) 1973-1980, 450 SL/SLC, M117, 2.65 / 3.06, 1.3 Liter
(W116) 1973–1980, 450SEL, M117, 2.65 / 3.06 / 3.07, 1.3 Liter
(W116) 1975–1980, 450SEL 6.9, M100, 2.65 LSD, 1.3 Liter
My 1978 300SD (W116) came stock with a 3.07 1.1 liter (185mm) differential.
Before I bought the car in 2014, the prior owner had swapped in a 2.47 1.3 liter (210mm) differential with the yoke change and half shaft change.
Low engine revs at highway speeds, but quite poor acceleration with that setup.
The engine developed a rod knock so it is non-operational for now, saving for an engine rebuild and a front suspension update.
In the meantime, the rear suspension has been fully redone including a differential upgrade.
I splurged with a Wavetrac differential professionally installed in a (R107) 3.06 1.3 liter (210mm) differential.
(08-09-2023, 04:11 PM)Echo575 I was wrong in that you can't get lower ratios than 3.46 here. I found a few 2.24 from w126 v8 but those are unusable since with my current tires rpm would be 1500 at 80 kmh and top speed in 1 gear almost 60 kmh. Price was high too.
(08-09-2023, 04:11 PM)Echo575 I was wrong in that you can't get lower ratios than 3.46 here. I found a few 2.24 from w126 v8 but those are unusable since with my current tires rpm would be 1500 at 80 kmh and top speed in 1 gear almost 60 kmh. Price was high too.
(08-09-2023, 10:05 PM)Alec300SD(08-09-2023, 04:11 PM)Echo575 I was wrong in that you can't get lower ratios than 3.46 here. I found a few 2.24 from w126 v8 but those are unusable since with my current tires rpm would be 1500 at 80 kmh and top speed in 1 gear almost 60 kmh. Price was high too.
Another option is to purchase a new 3.07 ring gear and pinion gear set for your 1.1 liter (185mm) differential.
The MB part number is A-123-350-14-39.
(08-09-2023, 10:05 PM)Alec300SD(08-09-2023, 04:11 PM)Echo575 I was wrong in that you can't get lower ratios than 3.46 here. I found a few 2.24 from w126 v8 but those are unusable since with my current tires rpm would be 1500 at 80 kmh and top speed in 1 gear almost 60 kmh. Price was high too.
Another option is to purchase a new 3.07 ring gear and pinion gear set for your 1.1 liter (185mm) differential.
The MB part number is A-123-350-14-39.