Differential Swap - Page 2 - PeachParts Mercedes-Benz Forum

DeliveryValve · #16 02-19-2007, 12:01 AM

I begining to think that I should put in the 2.88 ratio instead. I didn't see the post of questioning of my decision of continuing with the 3.07 ratio before I yanked it out of the SD.

In thinking about it, I found these other posts that are very interesting and useful information.

Well - I have found the MB diesel "easter egg" Swapping a 2.47 in a 300SD

1982 300SD Gets 2.47 Diff with LSD! Swapping in a 2.47 Limited Slip Differential

Differential dilemma - need your opinion Gearing discussion

2.47 diff in 300SD Another 2.47 swap

3.07 / 2.88 diff swap??? 2.88 swap discussion

w116 2.65 differential into a W123 adding a 2.65 Diff.

Hmmmmmmm.... What to do?.....

.......

dieseldiehard · #17 02-19-2007, 12:27 AM

put a 2.88 in it, it will still run up the Grapevice if the engine is running well (no chain stretch and valves lashed properly)
Putting an '85 differential from a 300D donor in my '83 300D was the best thing I've ever done to that car, next to replacing the timing chain (and that made a world of improvement!) and it was a fairly low mileage one that runs quiet!
And it turns out the speedo was reading high to begin with so the 2.88 made it calibrated again at no extra cost!
The original 3.07 gears were whining a lot and regardless of what people say, when new they don't whine, its after they wear that the gears don't mesh. As for rebuilding or swapping the pumpkin, if the mechanic doesn't have experience with that it will probably not turn out well as they will whine if the pinion nut is over torqued, its a very tricky job. A used low mileage diff is worth every bit of $175 or more as you can figure that if you drive a lot the fuel savings will pay for it over time. And there's lower engine wear if on the highway, ok I am a hard sell because I really like the 2.88 in a turbodiesel and its been said that should have been used from the factory to begin with!

JimmyL · #18 02-19-2007, 01:06 AM

I love the 2:88 rear end in the wagon, and it really is pleasant on the highway. Matter of fact, at 70mph I am doing exactly 0 rpm's. Dang, I really need to fix that tach......

I do love the 2:88, all kidding aside.

Cervan · #19 02-19-2007, 04:29 AM

you allways could just make everything abit more quiet and keep the rear stock.

DeliveryValve · #20 03-03-2007, 04:04 PM

After a long thought, I took the plunge with the 1984 300SD’s 3.07 differential. There are several factors to this decision. First, I drive mostly within the city with a lot of stop and go. I love the acceleration I get on this car, so I don’t want to mess with that setup at this point in time. Second, is the whining noise of the current rear end has become louder every week for the past month. Third, I only paid $40.00 for this differential so it is a cheap replacement. Fourth, to satisfy my original question “Would an early w126 Differential fit on a W123? Lastly, I don’t have to change out my speedo.

I documented the differential swap with some narration and pics.

1. Chock front wheels, Jack up rear of car, put on jack stands on the body hard points, place a bottle jack on rear suspension sub-frame, (as noted on the first pic) and remove rear wheels.

2. These next picture is my current 1983 300D 3.07 Differential prior to replacing my old axles.

3. Drain the fluid using a 14mm Hex bit. I got a set of hex bits (12, 14, 17mm) for $10.00 at Autozone with a lifetime warranty. The bolt is most likely on there tight, so I used the hex bit with my impact wrench. You can use a breaker bar also. Here is a shot of the gear oil after 300 miles of use. See the metal shavings?!!?
This link talks about Gear Oil, Hex Bits and has a shot of my differential when I was changing out the axles originally. Mobil 1 75W-90

Next, you have to remove the axles. One thread to note that has some great related information is from Jeremy5848 W123 axle R&R job--some questions? . He has some good tips in removing and reinstalling the axles.

4. In order to get to the axles you will need to remove the rear mount and differential cover. There are two 22mm Bolts (I actually used a 7/8 sae socket) to the cover and mount, four 13mm to the mount and body, and eight 15mm cover bolts as shown in the pic. To get to the upper cover bolts, simply lower down the sub-frame using the jack.

5. Here is a shot of my differential gear. The gear had these horizontal gouges on each tooth. I wonder if it is the cause of the whining sound?

DeliveryValve · #21 03-03-2007, 04:08 PM

6. Next step in removing the axles is to remove the “C” clips in the differential which hold the axles in place with a snap-ring plyers or a hook tool and the 13mm bolt on the hub of each wheel.

7. Drive the axles out of the hub using a thick rod and using a prybar on the other side.

8. You will have to remove the caliper in order to get the axle out. Also, you will need to jack up the sub-frame/differential to its highest point and let the suspension drop to the lowest point in order to get the axles out of the hubs. It is a tight fit.

9. With the axles out, remove the 15mm bolts for the driveshaft support bearing. I used a 15mm swivel socket. This will allow you to slid the driveshaft towards the front once you unbolt it from the differential flex disk.

10. Remove the flex disk. There is a 15mm bolt and a 17mm nut. Use a prybar to separate the disk from the driveshaft.

DeliveryValve · #22 03-03-2007, 04:14 PM

11. Here is a shot of myself removing the bolt of the flex disk with the differential out of the car.

12. The differential is connected to the suspension sub-frame with four bolts/studs. The front bolts are in a limited space area.

13. The rear bolts are a bit easier to get at.

14. To get to them, I used a ½ inch drive 19mm deep socket, a swivel head ratchet and a cheater bar. My swivel head ratchet is actually a cheap Harbor Frieght “stubby” set I purchased for 10 bucks. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46742

15. Shot of the wrench on the rear bolts of the diff. I was fortunate enough to have a true California car.... No Rust! The bolts came off nicely.

DeliveryValve · #23 03-03-2007, 04:17 PM

16. Down the differential goes. (notice the crack on the mount point. This cover actually came of the SD and I broke it while removing it from the car.. It was cross threaded and a b%$ch to get off!)

17. Shot of the Sub-Frame above where the differential goes and mounting points.

18. There is no axles or differential.

19. See pic, can you tell which differential is which?
What is the difference between the differential form the 1984 300SD and the 1983 300D?

Nothing! The housing is the same (PN#123 351 0101) and the Gears are the same (PN#123 353 0112 3.07).

(the one with the bolts on the four studs is the SD diff.)

20. Up goes in the new(used) differential.

DeliveryValve · #24 03-03-2007, 04:22 PM

21. Tighten the four bolts “Guten Tight”. There is no way you can get a torque wrench up there. So you will have to make sure it is on there tight!

22. I am replacing the two flex disks. They are actually in OK condition with few minor surface cracks, but since one is out, I will replace them anyway because Diesel Giant scared the sh&$ out of me. http://www.peachparts.com/shopforum/showthread.php?t=171761&highlight=flex+disk

23. Check out this disk from the SD. Notice the cracks. That is bad news for potential damage!

24. Here is a shot of the new flex disk. Remember to torque the bolts down to 45nm.

25. I installed new differential axle seals. To get them out, I liked using a hook-like prybar from harbor freight. They worked extremely well. It required some pressure but not to the point I am killing myself. I paid under 10 bucks for a set of these.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=7929

DeliveryValve · #25 03-03-2007, 04:25 PM

26. To install the seals, I like using a rubber mallet and a 3 lbs hammer. Put the mallet against the seal and tap with the hammer. Work your way tapping around it so the out edge of the seal is flush with the housing.

27. Once the seals are in place, install the axles. I used the original spacer and like to grease the “wheel” ends of the splines so it can slide in the hub easily.

28. Slide the axles in the differential and hubs (reverse order of removal procedure)

29. Install “C” clip. The spacing for the “C” clip was perfect!

After that reinstall the 13mm bolt on the hub.
Reinstall calipers with thread locker.
Reinstall differential cover and mount. Use a good silicone sealant for the cover and make sure you use thread locker on the mount to body bolts.
Reinstall tires and lower the car.
Add in differential fluid of choice and you are ready to go!

The result is this differential is SSOOOO much quieter then the original and it actually wasn’t that bad and a fun project to do.

DeliveryValve · #26 03-05-2007, 03:43 PM

Since I had the drive shaft center bearing loosened, I went ahead and replaced the front Flex Disk. Diesel Giant has some narley pictures of what can happen if the Flex Disk fails.

http://www.dieselgiant.com/Mercedes%20flex%20disc%20failure.htm

1a. You may have to loosen the driveshaft sleeve nut just before the center bearing so you can slide the driveshaft forward.

1b and 2. There isn’t too much room to work on the Flex Disk. You will need to remove the transmission mount. First support the transmission by placing a block of wood between a jack the transmission fluid pan. Then remove the four 17mm mount bolts and 13mm bolt. Remember to mark the position of the driveshaft flange relative to the transmission flange.

3. In order to get at the Flex Disk bolts, I used a 15mm swivel head socket and a 17mm box open end wrench. After removing all the bolts, use a prybar to separate the disk.

4. Install new flex disk with driveshaft flange in the same position as noted by the mark.

5. Reinstall all mounts and tighten driveshaft sleeve. Job is finished.

rudolfgreen · #27 03-05-2007, 07:45 PM

excellent diy, this needs to be archived.. and still dig my 2.47

Dieselkraut23 · #28 07-10-2007, 03:26 PM

Ok guys i have noticed no one has brought this up yet...what part or parts do you need to change to make the 2:88 work in a NON 85 300D?

is there a gear you swap from the tranny ...is there a gear in the speedo? what is it that will make it work besides other then the speedo cable?

also if you have to snag a gear from the tranny where it mates to the speedo cable how do you get it and can you?

winmutt · #29 07-10-2007, 04:44 PM

The only thing required is the correctly geared speedo.

rrgrassi · #30 07-10-2007, 04:58 PM

So then all you need is a 2.88 rear diff and the speedo from and '85 also? No need to change the speedo gear in the tranny?