W108 Rear Ratio Q - PeachParts Mercedes-Benz Forum

Bobsmyuncle · #1 10-30-2019, 05:51 PM

Hi folks, I found a wrecker with a W108 and I'd like to grab the rear end for a swap into my Fintail.

It's a 1970 280; 1080161204202 that is all I know for now as the hood won't open.

They won't lift the car for me nor will they pull the rear for me to have a pre-purchase look at the differential (I even offered to pay the labour).

I don't want to end up with gearing that my little 2.3 can't push up hill can anyone tell me what ratios were commonly used, or does the info I provided help determine that?

Any help would be appreciated!!

Here's a cool shot of my Fintail with a bit of opposite lock to say thanks!

Frank Reiner · #2 10-30-2019, 06:18 PM

Most likely ratio is 3.92:1. The tallest would be 3.69:1.

fonzi · #3 10-30-2019, 06:33 PM

I think some are over 4.0 too.

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Usaguy · #4 10-30-2019, 07:02 PM

if its a us model 2.8 280 then 1970 and older is 3.92 and 1971 and newer is 3.69

t walgamuth · #5 10-30-2019, 07:18 PM

Quote:

Originally Posted by Bobsmyuncle

Hi folks, I found a wrecker with a W108 and I'd like to grab the rear end for a swap into my Fintail.

It's a 1970 280; 1080161204202 that is all I know for now as the hood won't open.

They won't lift the car for me nor will they pull the rear for me to have a pre-purchase look at the differential (I even offered to pay the labour).

I don't want to end up with gearing that my little 2.3 can't push up hill can anyone tell me what ratios were commonly used, or does the info I provided help determine that?

Any help would be appreciated!!

Here's a cool shot of my Fintail with a bit of opposite lock to say thanks!

I don't know but a good guess is 354 or 369.

rwd4evr · #6 10-30-2019, 08:37 PM

I can't say for sure but I've never seen a 3.69 in any of my cars. Pretty sure my diesel conversion parts car is a 1970 280se and it's not 3.69. every swing axle car I've see besides 4.5 v8 cars are 3.92 and 4.08. I think the 3.69 was an option not a normal factory piece.

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Tony H · #7 10-31-2019, 01:49 AM

3.69 is from a 280SE 3.5

fonzi · #8 10-31-2019, 09:24 AM

Quote:

Originally Posted by Tony H

3.69 is from a 280SE 3.5

That must scoot! 3.46 is what the same drive train gets in a 107.

Www.Automobile-catalog.com is a pretty reliable source for differential ratios IMO.

I am pretty confident that the rear end that came out of the 1969 280s I parted was a 4.08, not a 3.92 like automobile-catalog says. I continued checking that site from 1970 back to 1967 for 280 w108, and the results I got going back were all 3.92 (despite being confident I pulled a 4.08 out of one).

Then I checked a 1972 280se and low and behold, automobile-catalog.com does say a 72 280se should have a 3.69.

But I think the only way to really figure out what any car actually has is to take a good look at the diff itself. I’ve had many scenarios where the ratio is not at all what’s expected and a couple of cars that were NOT purchased with the expectation of a desirable Diff ended up being a LSD with a great ratio. I’ve even purchased v8 cars that ended up having a 6 cylinder diff.

We are talking about 50 years of history here. Anything could have happened.

So just bring a jack, stands of some sort (JY wheels?), tarp, gloves, safety glasses, and a few wire brushes, some cleaning spray, and rags. Be prepared to get those gloves dirty scraping off thick greasy crud.

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Tony H · #9 11-01-2019, 04:07 PM

I installed a 3.27 in anticipation of my 560 project. Slowed it down quite a bit.

Quote:

Originally Posted by fonzi

That must scoot! 3.46 is what the same drive train gets in a 107.

Www.Automobile-catalog.com is a pretty reliable source for differential ratios IMO.

I am pretty confident that the rear end that came out of the 1969 280s I parted was a 4.08, not a 3.92 like automobile-catalog says. I continued checking that site from 1970 back to 1967 for 280 w108, and the results I got going back were all 3.92 (despite being confident I pulled a 4.08 out of one).

Then I checked a 1972 280se and low and behold, automobile-catalog.com does say a 72 280se should have a 3.69.

But I think the only way to really figure out what any car actually has is to take a good look at the diff itself. I’ve had many scenarios where the ratio is not at all what’s expected and a couple of cars that were NOT purchased with the expectation of a desirable Diff ended up being a LSD with a great ratio. I’ve even purchased v8 cars that ended up having a 6 cylinder diff.

We are talking about 50 years of history here. Anything could have happened.

So just bring a jack, stands of some sort (JY wheels?), tarp, gloves, safety glasses, and a few wire brushes, some cleaning spray, and rags. Be prepared to get those gloves dirty scraping off thick greasy crud.

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rwd4evr · #10 11-03-2019, 03:45 PM

Quote:

Originally Posted by Tony H

I installed a 3.27 in anticipation of my 560 project. Slowed it down quite a bit.

I have a 3.69 in my 450slc 4 speed and it's pretty quick. Od would make it perfect it's pretty screamy on the highway. I hope you didn't let go of that 3.69 swinger! I'd say it's quite valuable.

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Tony H · #11 11-04-2019, 01:06 AM

I did a long time ago. I realize I should not have.

rwd4evr · #12 11-06-2019, 04:12 AM

That sucks. I have two 3.27 LSD swing axles. I'd need a ton of money to let go of either of them. I wish one was 3.69.

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Benz Dr. · #13 11-06-2019, 08:06 PM

Quote:

Originally Posted by rwd4evr

That sucks. I have two 3.27 LSD swing axles. I'd need a ton of money to let go of either of them. I wish one was 3.69.

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That's interesting, I have a 3.27 LSD too. I figured that they were pretty rare but really didn't know if the 4.5 had a lot of them or not. I know they're very uncommon on the six cylinder cars except 300 SE where I think that was a standard feature.

What do think they're worth as is or as rebuilt units?

Dr. Sternschnuppe · #14 11-06-2019, 05:37 PM

Quote:

Originally Posted by Bobsmyuncle

It's a 1970 280; 1080161204202

Look like 3.92

Tony H · #15 11-06-2019, 05:49 PM

I have 2 3.27's also. I grabbed them whenever I saw them in the Pick n Pulls. Not to many 4.5's (or any vintage MB) in the yards anymore. The stuff I left behind thinking it would never run out. I used to have 8 pick n pulls within 1.5hrs now the closest one is 5 hrs away.