Changing rear end gears - PeachParts Mercedes-Benz Forum

buzztrader · #1 06-13-2006, 08:24 AM

Hi guys

I hope you do not hate me for this, but I used a 1982 300SD as a donor car to build a new driveline for my 1962 Rolls Royce. Not that I did not like the mercedes, I just liked the Rolls better.

Here is my question. The rolls has bigger wheels and the 3.0Litre turbo engine is sluggish moving the car even though its much lighter than the original mercedes. Mostly becuase of the increased diameter of the wheels.

I also have a 1973 450SL. I was wondering if the gears in the rear ends were interchangeable? The 450 is geared way to low and the 300SD is way to high. A swap would likely make both cars much better.

Does anyone know if they are the same?

Tomguy · #2 06-13-2006, 11:41 AM

The gear in the 450 I believe is a 3.07 - which I believe is also the same as what's in the 300SD. Someone can correct me if I'm wrong but that's what a search of this forum turned up.

Arthur Dalton · #3 06-13-2006, 11:54 AM

Quote:

Originally Posted by Tomguy

The gear in the 450 I believe is a 3.07 - which I believe is also the same as what's in the 300SD. Someone can correct me if I'm wrong but that's what a search of this forum turned up.

All the ones I see are 3:27 . but I will check one.

t walgamuth · #4 06-13-2006, 08:38 PM

early 450s used a different gear from later ones. according to mb buyers guide, 307 thru 79, and 265 80 and later. it doesnt mention a 327.

tom w

Arthur Dalton · #5 06-14-2006, 09:23 AM

Quote:

Originally Posted by Tomguy

The gear in the 450 I believe is a 3.07 - which I believe is also the same as what's in the 300SD. Someone can correct me if I'm wrong but that's what a search of this forum turned up.

That is correct and also what I found.
The mentioned 3:27 would be from the earlier 4.5 108 chassis [ which is a swing set-up]

t walgamuth · #6 06-14-2006, 07:22 PM

Quote:

Originally Posted by buzztrader

Hi guys

I hope you do not hate me for this, but I used a 1982 300SD as a donor car to build a new driveline for my 1962 Rolls Royce. Not that I did not like the mercedes, I just liked the Rolls better.

Here is my question. The rolls has bigger wheels and the 3.0Litre turbo engine is sluggish moving the car even though its much lighter than the original mercedes. Mostly becuase of the increased diameter of the wheels.

I also have a 1973 450SL. I was wondering if the gears in the rear ends were interchangeable? The 450 is geared way to low and the 300SD is way to high. A swap would likely make both cars much better.

Does anyone know if they are the same?

you think the roller is lighter than a benz? seems unlikely. do you have weights?

tom w

mercmad6.3 · #7 06-15-2006, 10:15 PM

Rolls Royces were a meduim speed car,certainly not fast because of the bulk of the heavy body they had to haul around.your problem has nothing to with the rollers rear end ratio which i think you will find to be about 4-1.If anything the diesel is probably revving it's guts out and 3 liters in not enough to hual a car normally moved by a engine with a capacity of 6 liters and close to 3 ton weight.
you would have been better off installing a Cummins from a dodge ram.
...or a Kenworth

t walgamuth · #8 06-15-2006, 10:58 PM

iirc the rolls engine is basically a clone of the big block chebby cast in aluminum. i think it is more likely to be running a 1,92 rear end than a low gear. the benz motor is probably having a tough time pulling the weight around against a tall rear end.

tom w

wbain5280 · #9 06-16-2006, 01:41 AM

Rolls are very heavy cars. Check the curb weight in the owners manual. That 120 HP diesel is overstressed.

Get a big block Chevy, you need the torque.

t walgamuth · #10 06-16-2006, 05:54 AM

i looked in my 'collectable cars' book last night and found that for 62 the lightest rolls listed is well over 4600 pounds. about 1000 more than a benz.

the stock motor is a 380 cubic inch jobber. probably rated at 200 to 250 hp (rolls never listed hp, just stated it was adequate). probably 300 to 350 torque.

i would estimate that the rear end ratio with the taller tires to be maybe 307 or so.

you can determine the ratio by turning one wheel one full turn and counting the times the pinion turns and multiplying by two. if it has a posi and both wheels spin you wont need to multiply by two. you wont have a precise number but there is not an infinate number of gear combinations available so you should be able to get close enough to get it.

to get reasonable performance from your setup i would think you need a 369 or 390 rear end ratio.

tom w