Hey Benz Guys,

I'm in need of some instruction. I am contemplating the replacement of the differential and I'm in need of some procedural instruction. I've already purchased the replacement, and it is enroute, however, my questions in the meantime are: "Is it as simple as removing bolts, removing the old and installing the new? Or, is it something that I'm going to need pry bars, slide hammers, etc? Am I going to have to tow it for while (let it cool), drive it for a while (being easy) and let it cool? What am I in for, is the question? Is this something I should attempt to do on my own, or defer to someone else?" I'd really appreciate if you guys would respond to my questions. Thanks.

 

Pumkin. Unfamiliar term.
So what are you trying to do. Change the diff?
If so this is not a 5 min job due to IRS.
Stuart

 

LoL! Yeah, Stuart:

The differential housing is sometimes (at least in my area) referred to as the "Pumpkin" or the "Hoghead." In either case were talking about the Rear Differential.

Now, what or how does this relate to the IRS, again? You missed me with that one!

 

Hi,
I'm familiar with BANJO on a solid axle.
IRS = Independent Rear Suspension.
So what are you trying to achieve. Replace the diff? Why?
Access is the issue.
Stuart

 

Hello Stuart,

Now I've got another one to add: "Banjo." Funny! And the "I.R.S." That will scare some folks and confuse others. lol.

Yeah, well, Stuart. Over the past few months, I've noticed a high pitch whine coming from what I now know, is the rear end. At first it was difficult to isolate, due to resonance. I initially thought it was the rear wheel bearings making the roaring, scrubbing sound. But as it turns out, it's the same sound. The pitch changes at acceleration to a high pitch whine, which I thought might even have been the Transmission, but there's no slippage, and it shifts fine, and engages fine.

At 30 mph it's a roar, but at 40, 50, 60 mph it's an escalating high-pitch whine, like a turbine. At 75 to 80 you can't even hear it, but I get this feeling of resistence, as if the wheels are not free to roll. It feels sorta like the wheels are partially being dragged, or are laboring to roll. But as you de-accelerate, the de-escalating noises all whine back down to the roaring scrubbing sound, like a turbine bearing gone bad. I thought maybe the fluid was low, but the fluid wasn't low enough for that to occur. So, I had the fluid drained, and what came out was an incredible amount of silver specks and metal shavings. It was so much metal that it seemed like the fluid was a different color, but not so, it was just that much metal. Fresh fluid did not improve matters either.

On the highway, when I deliberately turn the wheel from side to side so as to weave, there's no looseness or change in wheel noise to indicate wheel bearing. Then I thought that there might be a loose or fatigued spring in the rear brake-shoes that might be scrubbing against the hub, but we will have to go through this process of elimination. I will have to replace the rear swaybar links, but that's about all that I can readily tell.

As for the Differential, well, I'm not wanting to go into the housing, I read about all the tools I would need and the process of changing out the differential from the housing, and I'm really not interested in doing that, I just want to replace the whole mid-section, the pumpkin, or the Banjo, as you called it.

And again, I want to know is this something I can do myself with relative ease, or would It be better to have someone else do the do?

Hey, the vehicle is 10 years old with 238K on the clock, it's time for some stuff to just be replaced. And as it so happens, the Hoghead is one of the items needing replacement. So, I'm not mad, I just wanna get it done.

Thanks for your help in advance.

 

LOL. I hadn't considered that IRS also spells Inland Revenue Service. Its that time of year!!

Banjo is the term sometimes used for a solid rear axle.

So the oil was drained from the diff? OK so you have a bad bearing or more likely crown wheel and pinion. Fits the description.

A complete swap out shouldn't be a big problem but ensure you get the correct ratio!

Never swapped a diff complete but basically its just a matter of uncoupling the driveshafts and prop shaft.
However to diconnect the driveshafts you may have to "break" the lower rear suspension joint to give sufficient room to pull the driveshaft away from the diff.

All heavy stuff and not recommended without a wheel free lift.

May also have to remove the rear exhaust system.

Sorry can't really help much more.

Stuart.

 

Thanks for your input, Stuart.

I'd rather replace the mid-section than to go into the housing and messin around with stuff I don't know nothing about, especially when I'm not going to give myself a warranty. I don't have the inclination nor the time. As far as ratio is concerned, if the Differential being replaced is of the same year and make, would there be need to be concerned about ratios? I guess if it was a diesel perhaps I would have to be concerned, no? I know the S420 and the S500 for this year and make share the same differential. Otherwise, I'm sure it would total jack-up my speedometer for sure, huh?

I'm still waiting for my 16" wheels to come in (I can't wait either) so I can go back to the ride I once had. I put some Lesjefor Springs on the front, now it sits too high. As far as settling, I don't know if there going to settle much more. I'm definitely going to replace these springs with stock (oem) which is what I thought I was getting, but obviously not. The rear springs I'm not concerned with as much, but the front's got me looking like a "bobble-head doll." I can't have that!

The alignment is still off. The castor is off. According to the printout, the specified range is 9.2 degrees to 10.2 degrees for each wheel. The right is maxed at 10.2 degrees, and the left is at 9.0 degrees, and steering wheel is not center. The turn signal cut-off at approx. 30 degrees before center. And I can feel the difference, especially with the front sitting so high.

Oh, well, I'll get it right in bit, I guess. I just hate the nickel and dime approach, but hey, it's not like it's a new vehicle. So, I'll take my time and get it right. I still have a BMW to be concerned with as well. Gotta pace myself here.

Anyway, thanks again for your help.

This board seems wierd these days, what's going on. The responses don't come as quickly as they once did. I'll tell you something else. Ever since we found out that Lugnut passed, and Sleepwalker started experiencing his challenges, which I haven't forgot him either (things are just wierd all around), the board just don't seem to have the same fire as it once had. hmmmm. oh well.

But thanks. In a lot of ways your posts remind me of Lugnut, to a degree.

Take care, Stuart. Let you know how I come out.

Peace,

David

 

OMG You compared me to Lugnut!

So long as the diff comes from the same type vehicle and you ensure the gas/diesel issue you should be OK.

WRT the front springs. if the ride height is incorrect this will impact the geometry.

WRT the turn signal etc the CORRECT procedure for alignment/geometry on a Merc is to first set up the vehicle.
Sills must be level and a four wheel system used in order to determine the correct longitudinal and transverse axis.
The steering wheel/column should also be locked in straight ahead.
Dependent upon model there is often a pin to position the box/rack in the straight ahead position. When this is inserted the steering wheel etc should all be straight ahead. If not they need to be repositioned.
Only then you set each front (and rear wheel if adjustable0 to the correct geometry.
When you drive the car you will then find it goes straight (subject to good tyres).
Stuart.

 

Okay, Stuart:

Got me sorta curious here. P/N: 129 351 06 05 Shows this housing as being the part for all S420, 1997-99.

How would I know whether it is specifically for gasoline engines, or a diesel engine? Are there other markings on the housing to further indicated whether it's for gas or diesel?

 

David,

If the parts catalogue only shows one part number for all variants looks like you have the correct one.
I know very little about the S range 97-99. Maybe the diesel was not a 420 but a 320 or similar. Maybe there wasn't even a diesel in the range!
Manufacturers like to reduce complexity. Looks like they achieved this goal.

A diesel engine pulls say 5000 revs while a gas pulls say 6000. This is why the diff has to be potentially different.

I'm sure that you have the correct diff. I just wanted to warn that ratios or part numbers checked before parting with your cash.

Good luck,

Stuart