Rear-end gear swap? - Page 2 - PeachParts Mercedes-Benz Forum

stimpy451 · #16 11-24-2009, 04:55 PM

Quote:

Originally Posted by DeliveryValve

Thanks for the correction, I am Lysdexic.

fixed

swheele2 · #17 11-24-2009, 05:26 PM

Quote:

Originally Posted by DeliveryValve

Thanks for the correction, I am dyslectic.

No problem.

okyoureabeast · #18 11-24-2009, 05:28 PM

Quote:

Originally Posted by DeliveryValve

Ok, I was exaggerating. But it will be very slow take off.
The 220D has an output of something like 55 horsepower and 90 lb ft of torque.
Your 300D has an output of something like 125 horsepower and 181 lb ft of torque.

The 220D needs all the help it needs to accelerate from a stand still compared to the 300D. For the final gear ratio, a 2.88 ratio means for every one driveshaft rotation, the wheels turn 2.88 times. With a 3.90 ratio, for every one rotation, the wheel turns 3.90 times. The 2.88 makes it harder for an engine to get up to speed with less revolutions. The 3.90 makes it easier for an engine to get up to speed with more revolutions.

If you ride a bike, think of climbing a hill with it. You have to shift gears to peddle faster so it easier to get up the hill.

.

That makes a ton of sense. Thank you very much!

seanarcher · #19 01-10-2010, 10:23 AM

so where can i find a 2.88 rear gear that will fit a 123?
what models have this gear?any links or articles would be appreciated?
what mods are required to make a 126 or maybe a sec model diff fit a 123?

Somebody should have or make a chart of interchangeable rear ends.

snookwhaler · #20 01-10-2010, 11:17 AM

Quote:

Originally Posted by seanarcher

so where can i find a 2.88 rear gear that will fit a 123?
what models have this gear?any links or articles would be appreciated?
what mods are required to make a 126 or maybe a sec model diff fit a 123?

Somebody should have or make a chart of interchangeable rear ends.

85 300D/SD is a direct fit. There may be some others.... I have forgotten more than I know at this point.

I just replaced mine. They are out there and are pretty cheap. I just swapped mine out because mine was questionable as well. It was not that difficult of a job albeit a little time consuming. I have never liked laying underneath cars that are on jack stands. Either way, I got it done.

seanarcher · #21 01-10-2010, 01:05 PM

I am pretty sure that any same body differentials can be used on that same body.I would really like to know what differential I could use on a w123 from other body styles with and without mods.preferably without modifying.

did you go to a different size gear when you swapped you differential?

for now i would like to go to a taller gear in a 123 or 126.possibly the 2.88 or lower..
would i be able to use the speedometer gear from the same body...and wich one(s)would i replace/swap?
I guess i need to keep searching the archives.

I just read a mercedes production book by nitske...how correct are his books?

#22 01-10-2010, 01:14 PM

I believe you will have to find a replacement speedometer head from a 85 W123 if you install 2.88 gears.

okyoureabeast · #23 01-10-2010, 01:23 PM

Quote:

Originally Posted by Craig

I believe you will have to find a replacement speedometer head from a 85 W123 if you install 2.88 gears.

That is correct. You'll need to match the speedometer to the differential.

daw_two · #24 01-10-2010, 01:44 PM

Quote:

Originally Posted by Craig

I believe you will have to find a replacement speedometer head from a 85 W123 if you install 2.88 gears.

Used speedometer heads and 2.88 rearends are available if you look in the Parts Forum.

snookwhaler · #25 01-10-2010, 02:49 PM

Quote:

Originally Posted by seanarcher

I am pretty sure that any same body differentials can be used on that same body.I would really like to know what differential I could use on a w123 from other body styles with and without mods.preferably without modifying.

did you go to a different size gear when you swapped you differential?

for now i would like to go to a taller gear in a 123 or 126.possibly the 2.88 or lower..
would i be able to use the speedometer gear from the same body...and wich one(s)would i replace/swap?
I guess i need to keep searching the archives.

I just read a mercedes production book by nitske...how correct are his books?

You did not specify which car you own so not much to go on. Assuming its a 123 from the sounds of it.

Yes, any diff. from any 123 will work. That is a given.

Any diff. out of a 81 to 85 126 will work too. There are others.. But, I have forgotten. Some gas rear ends will work too. I forget the bodies.

No, mine had a 2:88 in it already and I went back with the 2:88. I thought about going with a 3:07. But, after thinking about my driving habits (mostly highway), I went back with the 2:88. If I lived in the inner city, I would surely have gone with the 3:07.

Gearing "Lower" means going "numerically higher". And gearing "higher" means going "numerically lower". So, assuming you want to gear it "higher" you can go all the way to a 2:47 from a gasser. But, you will suffer low end power loss and have sluggish take offs. The 2:88 is a good compromise IMO.

There are some other factors too though. If you car is an auto. or manual will make a difference in how you gear it.

seanarcher · #26 01-10-2010, 11:39 PM

Quote:

Originally Posted by snookwhaler

You did not specify which car you own so not much to go on. Assuming its a 123 from the sounds of it.
I have a 123 turbo sedan

Yes, any diff. from any 123 will work. That is a given.

Any diff. out of a 81 to 85 126 will work too. There are others.. But, I have forgotten. Some gas rear ends will work too. I forget the bodies.

No, mine had a 2:88 in it already and I went back with the 2:88. I thought about going with a 3:07. But, after thinking about my driving habits (mostly highway), I went back with the 2:88. If I lived in the inner city, I would surely have gone with the 3:07.

Gearing "Lower" means going "numerically higher". And gearing "higher" means going "numerically lower". So, assuming you want to gear it "higher" you can go all the way to a 2:47 from a gasser. But, you will suffer low end power loss and have sluggish take offs. The 2:88 is a good compromise IMO.

There are some other factors too though. If you car is an auto. or manual will make a difference in how you gear it.

what parts would i need to swap out of my speedometer if i went with a different differential?

i would like to go to a taller gear...or a 5 speed,i think ill have an easier time finding the gear though.

okyoureabeast · #27 01-10-2010, 11:43 PM

Quote:

Originally Posted by seanarcher

what parts would i need to swap out of my speedometer if i went with a different differential?

i would like to go to a taller gear...or a 5 speed,i think ill have an easier time finding the gear though.

Just the spedometer from the car you pulled the differential out of. It pulls right out of the instrument cluster with 4 screws.

Matching your mileage may be a bit more difficult, but rolling the odometer doesn't seem like a very difficult task.

snookwhaler · #28 01-11-2010, 06:21 AM

Just be sure that what ever car you decide to get the rear end from comes with the matching speedo/odo. There are part #'s for all of this stuff on the site somewhere. I remember reading it before.

Changing out the speedo takes about 15 minutes if you have done it before. A little longer if you haven't. Not that big of a deal. You basically just push the thing out, remove the speedo cable, oil press line and a couple plugs. Be careful removing and installing the screws that hold everything in the back of the cluster and DO NOT over tighten those little screws or you will "crack" the little towers that the screws "screw into" (ask me how I know).

MBZ123 · #29 01-11-2010, 06:32 AM

Quote:

Originally Posted by stimpy451

Maybe it's just because I have a big-ass hole in my muffler,

When I first read just that fragment, bout fell off my chair! Was gonna ask how you managed to stuff 'em in there, lithium grease? Ahhh, late nights are so fun.

FNHB