Thought my issues was flex discs but I believe was wrong

[spree17]

Thought my issues was flex discs but I believe was wrong

Put car on jack stands and watched the drive shaft. It seemed to turn normally without issue.

I have narrowed it down to a few possibilities:

Low differential fluid (it hasnt been checked in 50,000 miles or more)

Brake issue on drivers side

Bad differential or axle issue on drivers side. There are 2 metal wheels. One on each side of the differential box. 1 seems fine. 1 seems a tiny bit off or warped.


Hesitation only occurs at stop lights or red lights. Doesnt occur unless starting from a stop when I had foot on brake.

Drives perfectly once moving.

I put the cars rear end up on jack stands and reved the wheels. Problem only noticable after tepping on the brake. Felt brake vibration on brake pedal when I would rev the weehsl hard and then hit the brakes.

I took the wheels off but couldnt tell if there was a brake issue.

I tried to check the differential but those drain plugs are in tight and I dont have a 14mm hex socket. I may take it in to have the differential fluid changed unless anyone has any other ideas. I have heard there are some real good differential additives out there. Does anyone recommend any?

[tbomachines]

I'm not sure what your "issues" are - is it the brake vibration? That would point toward warped brake rotors (chances are a visual inspection of them would not see the problem). "Hesitation occurs" - sounds like the transmission, but if you could describe it better we could be of more help.

[spree17]

It is a legit hesitation that only occurs at stop lights or red lights it is accompanied by some noise. Doesnt occur unless starting from a stop when I had my foot on the brake. Sometimes rpm will go as high as 2000 before things go normally from the stop lights. Doesnt have any issue even if rolling as low as 3mph. Only happens from complete stops. I seem like I can sometimes manipulate the issue not to happen if I let go of brake gently and step on gas slowly. Drives perfectly once the car starts moving.


I just called a place to get my differential oil changed. He said $45. Is that normal? I wish I could find a 14mm hex socket. I would change it myself.

[Stretch]

So are you saying you've got an automatic gearbox that slips when you start from a stand still but doesn't slip when you are still rolling in gear?

[babymog]

Sure sounds like what he's saying.

I've had a couple of transmissions with low pressure, wouldn't downshift into 1st until you started to roll / built RPM, then it did it with a thump. Maybe this is what he's (not) describing?

[spree17]

Thanks for the reply guys.

If the wheels are moving at all (even as low as 3mph) the car drives beautifully with no issues.

The problem is noise and hesitation only when starting from a complete stop like at a stop sign or a red light.

I just drove it around 10 miles and the noise seems to be coming from that axle area. I'm going to attempt to check the axle oil and replace it.

I put the car in neutral and cruised around 20mph. I didnt feel any brake issues when doing that.

[spree17]

Originally Posted by babymog

Sure sounds like what he's saying.

I've had a couple of transmissions with low pressure, wouldn't downshift into 1st until you started to roll / built RPM, then it did it with a thump. Maybe this is what he's (not) describing?

Sounds similar but the noise really seems to be from the rear axle differential area.

[gear-head]

I seriously doubt there's any real problem with the diff, you'd know something was really up with the diff whenever you turn a corner, the tighter the turn the more noticeable it would be, and it would be VERY noticable too. That's really the most likely indication that there might be something wrong with the diff, turning corners! Doesn't hurt to have the lube level in the diff checked though, could probably have that done quick and relatively cheap at most any lube place, your problem may very well lie with a sticking brake caliper. That "run out" issue you described albeit very confusing sounding, on what sounds like the "can" on the axle halfshaft probably isn't a real issue either. Those are just "cans" with lots of clearance room and filled with grease. As long as your boots aren't torn (they aren't torn, are they?), your axles are mostly likely good to go too. Focus on the brake calipers and just plan on rebuilding them just as a part of regular preventive maintence anyway. Replace the pads when your done AND the rotors, Mercedes rotors don't allow for a whole lot of extra material in the rotors for machining, they are considered a replacment item when doing a brake job, that will eliminate run out in the rotors and another potential for effecting the way the brakes release. Also just as importantly are the brake hoses, if they are the original ones, the rubber inside can be deterioating and can restrict the proper flow of the brake fluid and could impede the pressure relief when you lift your foot of the brake pedal, again replacing the hoses is cheap, easy and part of regular preventive mantience. See if that doesn't help before going off the deep end into axle replacement or opeing up the diff. (That is, unless your axle boots are torn, in which case, you know what's next!)

[spree17]

Thanks so much for all that info gear head.

I just got the fill plug out and it seems like the gear oil is low if not toast. I wanted to replace it but I cant get the drain plug to turn. I'm using a 9-16 hex socket not the 14mm. Autozone guy told me they were the same. It worked for the top plug but the drain plus doesnt want to hold it in place enough to budge the drain plug loose. I just shot the plug and area with liquid wrench. Maybe that will help.

I will change the gear oil. If that doesnt do it I will have to drive to the dealer and let them tell me what it is. I cant afford to keep guessing and replacing parts on the car till I find the real issue.

[pawoSD]

Originally Posted by spree17

Thanks so much for all that info gear head.

I just got the fill plug out and it seems like the gear oil is low if not toast. I wanted to replace it but I cant get the drain plug to turn. I'm using a 9-16 hex socket not the 14mm. Autozone guy told me they were the same. It worked for the top plug but the drain plus doesnt want to hold it in place enough to budge the drain plug loose. I just shot the plug and area with liquid wrench. Maybe that will help.

I will change the gear oil. If that doesnt do it I will have to drive to the dealer and let them tell me what it is. I cant afford to keep guessing and replacing parts on the car till I find the real issue.

Socket securely in the plug + breaker bar + floor jack. THAT will break it loose. I nearly lifted one of our cars off the ground once by the drain plug before it broke loose.

[d.delano]

Originally Posted by babymog

Sure sounds like what he's saying.

I've had a couple of transmissions with low pressure, wouldn't downshift into 1st until you started to roll / built RPM, then it did it with a thump. Maybe this is what he's (not) describing?

Would that be low pressure or low vacuum? I think I might have a problem with that. It will only do it once first thing on a cold morning though.

[spree17]

Originally Posted by pawoSD

Socket securely in the plug + breaker bar + floor jack. THAT will break it loose. I nearly lifted one of our cars off the ground once by the drain plug before it broke loose.

Used your breaker bar advice. I had to tap the socket in with a small sledge hammer but it worked!!!!

What are people thinking when they put these plugs in? I'm convinced the past mechanic used an impact wrench on everything.

Thanks for the good advice.


Does anyone have any advice on getting the new gear oil in? There are 2 cables that make it hard to lift the bottle enough for the oil to flow fast. I got more on myself than in the hole at times.

[JohnM.]

Most auto parts stores, or Harbor Freight have a cheap hand pump that will fit the threads on the gear oil bottles. Made especially for the job.

[spree17]

Originally Posted by JohnM.

Most auto parts stores, or Harbor Freight have a cheap hand pump that will fit the threads on the gear oil bottles. Made especially for the job.

Thank you. Any chance you have a link to a picture of one so I know what to look for?

I have cheap hand pump siphon but I have never been able to get it to work. I will look next time I'm at the store.

[Stretch]

Here is a picture of my vacuum pump - I was draining fuel from my tank when this was taken...

I hope it gives a rough idea. It is a simple plunger assembly - one pipe in - one pipe out.