2.47 Diff swap into 300td questions - PeachParts Mercedes-Benz Forum

snowtire · #1 01-05-2012, 12:28 AM

My first post on Peach. Apologies for cross posting from another forum. It seems like there is lots of knowledge about diffs here. Here goes:

I am in the middle of a big rear end rebuild project on my 300TD. Basically everything from the transmission back is getting refreshed: flex discs, driveshaft bearing, all bushings, axles, SLS delete, etc.

I stopped by the Pick-n-Pull today and picked up a 2.47 differential from a 1983 500SEC (W126). It appears to be in great shape, with no perceptible gear lash. I am going to swap this while, as they say, I am in there.

My questions are:

1) What shims from the current W126 axles do I need to retain for when I put the W123 axles in?

2) Should I just take both diffs to a specialized rear end shop to have them swap the input yoke in, or should my mechanic be able to do it?

3) Do I need to worry about lining up the new differential so that it is coaxial with the driveshaft and transmission? I read a post:

still looking for 2.47's which will fit w123

where the member spent some significant effort putting washers in the diff mount, the center bearing support, and even the trans mount in order to get them all pointed at each other correctly. Seems like it makes sense. What happens if I just bolt it up? Any experience with a diff swap from a W126 gasser?

vstech · #2 01-05-2012, 07:38 AM

Welcome to the forum!
Sorry your thread got blocked, new members cannot post links of any kind for the first few posts, (it's an anti-spam filter)

the spacers that came in the diff should stay there. make sure you pulled all the spacers from the axles on the donor car, and you should be good to go. I'd pull the axle seals, and replace them with new, to prevent leaks. as far as the yoke goes, it's got the preload set... you'll need to have tools to measure this, and I think there is a crush washer in there, that's gotta be replaced with a new one...
more experienced Diff mechanics will chime in on this one.

cho · #3 01-05-2012, 08:51 AM

Quote:

Originally Posted by snowtire

My first post on Peach. Apologies for cross posting from another forum. It seems like there is lots of knowledge about diffs here. Here goes:

I am in the middle of a big rear end rebuild project on my 300TD. Basically everything from the transmission back is getting refreshed: flex discs, driveshaft bearing, all bushings, axles, SLS delete, etc.

I stopped by the Pick-n-Pull today and picked up a 2.47 differential from a 1983 500SEC (W126). It appears to be in great shape, with no perceptible gear lash. I am going to swap this while, as they say, I am in there.

My questions are:

1) What shims from the current W126 axles do I need to retain for when I put the W123 axles in?

2) Should I just take both diffs to a specialized rear end shop to have them swap the input yoke in, or should my mechanic be able to do it?

3) Do I need to worry about lining up the new differential so that it is coaxial with the driveshaft and transmission? I read a post:

still looking for 2.47's which will fit w123

where the member spent some significant effort putting washers in the diff mount, the center bearing support, and even the trans mount in order to get them all pointed at each other correctly. Seems like it makes sense. What happens if I just bolt it up? Any experience with a diff swap from a W126 gasser?

hello snow

in due my engine conversion I have had chance to drive gassers diff on 300turbo

2.24 is slow dog (loooooong gear shift)
2.47 ok,starting is bit slow,no end speed on highway
2.88 - die beste !!

just jockin' if you like smooth and SILENT drive than 2.47 is ok

since you get gen1 w126 diff it should be no problem swapping

anyways there is good info here:

PeachPartsWiki: Replacing the Differential

regards
ChO

edit: I do hope that 300TD means turbo, because over here in europe we sometimes confuse those names, if your car is NON tubro,... forget about 2.47

vstech · #4 01-05-2012, 09:48 AM

Quote:

Originally Posted by cho

hello snow

edit: I do hope that 300TD means turbo, because over here in europe we sometimes confuse those names, if your car is NON tubro,... forget about 2.47

although he did not mention it in his post, his profile states it's an 85 TD so that SHOULD mean it's a station wagon, and yes it should be turbo.

snowtire · #5 01-05-2012, 09:58 AM

I don't have the in-lb torque tools, and I'd be more relaxed on long road trips knowing someone had set up the preload correctly. The input yoke on the 2.47 is the same design as the one on the 2.88, just larger diameter. It has to be swapped out.

My car is a turbo 85 model, which means it already has the 2.88. It is great, but our speed limits in the western US are 85 in many places and the car feels pretty revved up at those speeds. I'd like to go at 85 or 90 more quietly and with the engine in a lower rev range. I don't foresee any circumstance under which I would be frustrated with a top speed that is limited by engine power rather than by rpm governor. In other words, I don't care that the car's top speed drops from 110 to 100.

An added bonus that I am going to offset some of the cost of all of this work by eventually selling the 2.88 and the SLS parts I am pulling out.

cho · #6 01-05-2012, 10:02 AM

.

in that case you will ENJOY smoother and even more silent ride with 2.47

regards
ChO

vstech · #7 01-05-2012, 10:01 AM

awww. you are pulling the SLS system out? that's too bad. it's the best system MB has in any car...

snowtire · #8 01-05-2012, 10:19 AM

Yeah, I know pulling the SLS is controversial. I'll do a thread about it when it's all done. The choice to do the differential was a "while we are in there" kind of thing that followed a decision to do trans seal, flex discs, subframe bushings, and trailing arm bushings.