My trip to the dealer today...

[JHZR2]

Hi,

My ATF was last replaced by an independent shop, and it has alwyas been at the right level, but there are tiny fittle bubbles on the dipstick. Fearing aeration might be reducing the quality of the fluid (I dont know what brand was used, but it was put in by an MB only shop), I figured Id take it to the deale to be changed.


I got in, and when he saw my car, he was very hesitant. He asked me if Ive ever done ti before, all the typical stuff that people will ask when dealing with an older high mileage car, so the trans doesnt die as soon as the fluid is changed.

I told him that in the last 50k since I got the car, Id had it done twice, and the trans is still fine. He said OK, and went to have it done, as well as look at the vac modulator to check, because at cold startup, the shifts are either slow or real hard. (I figured theyd want to sell me some service so I ought to have them diagnose it). He also then told me that trans fluid should only be changed every 60k in general in these old cars, because changing it too often will loosten up too much dirt and then it wont shift right and may slip completely. I like 24-36k, personally...

Eventually they came back and said that the fluid looked clean, so I shouldnt change it. They also told me that I needed to change the 'piggyback' vacuum valves (P/N 002 997 53 36) which are the vacuum valves on the valve cover that control the trans shifting. They siad they were worn almost all the way. They would replace them to the tune of $325.

The also told me that the caster blocks (P/N 123 330 13 35), aka guide rod mounts were bad. They would change them for a cost of $560.

I know that my front end makes a knocking sound every time that my wheel is turned far to the right or left. Used to do it once each way, now it does it twice. also hear a clunk when I abruptly let on or off the throttle when driving slowly. Would that be because of the guide rod mounts?

Would worn vacuum valves effect cold shifting, but allow 100% fine shifts when warm?

Unless there is something tricky about the changing of the trans valves, I will do that myself. They are $36 at fastlane and should be ab easy job.

I have read that the guide rod mounts are reaql tough to do on the 300D, because you have to remove the spring. That is not something I want to tackle.
Is there any way that the guide rod mounts can be done by a driveway mechanic without screwing around with the springs? Most likely Ill have the indy do that though...

Any info on these things would be great.
Thanks,

JMH

[Ken300D]

If you run a search on guide rod mounts you should find some information on now to do the job without removing the springs.

You do have to be set up with a come-along, because you must jack up one side and apply pulling force to move the hub forward. Got to have wheel chocks under the car, etc.

It's a little scary but doable. Certainly improves the handling of the car and gets rid of the characteristic front-end pops.

Ken300D

[JHZR2]

I did search, but managed to read all the tales of trouble and difficulty... Guess I picked the wronfg threads in the archive

I dont think I want to learn by making this my first ever front end work to do in my freezing driveway...

Thanks!

JMH

[suginami]

What are guide rod mounts?

Are these tie rod ends or bushings?

The little valves on the valve cover are about a 10 minute job to replace. Pull two little pins and put the new ones on. Take a picture or draw a picture of the way all the hoses hook back up just in case you forget. $300+ for a dealer to do this?!!! Man talk about a scam

[engatwork]

If you look at the front suspension, lower control arm you will see a "rod" that runs from the bottom of the control arm back to the rear part of the fender well. The "track rod mount" is the part that the rear part of the rod mounts onto. It is an integral alignment part. The way I do it is to use another cars tow hitch and attach one end of a come-a-long to the hitch and the other end around the lower control arm between the spring and the spindle. Use the come a long to pull the lower control arm forward while you loosen up the alignment "adjustment" at the track rod mount end. It will eventually unscrew. At this point you will need to tighten the come a long just a little more to get enough clearance to replace the track rod mount. Take your time with this job and don't pull the lower control arm anymore forward than you absolutely have to.

[WANT '71 280SEL]

Where could I buy these guide rod mounts? My 1979 300SD has a cluck when braking and I believe that these may be my problem. I have already received my U. control arms, outer C/A bushings, and lower ball joints. I am looking on fastlane and I can't find any.
Thanks
David

[jbaj007]

Call Phil at FastLane/PartsShop (1-888-3334642). He has access to stuff not on the online catalog. He's very helpful.

Edit: Even Phil, though, wouldn't find guide rod mounts for a 116 (it doesn't have 'em). Thanks Sixto

[engatwork]

Would you expect a problem if I simply used the tow hitch at the rear of the very same vehicle upon which I'm replacing the rod mounts?

If the trailer hitch is mounted on the front you may be able to use it. If it is on the back you will be pulling the lower control arm the wrong way to get the clearance you need to remove/replace the track rod mount. I wish I had taken a pic of the set up when I did this procedure. Next time I do one I will get a shot of it to post.

I have about come to the conclusion that another source for front end noise is the sway bar bushings.

[sixto]

Originally posted by WANT '71 280SEL
Where could I buy these guide rod mounts? My 1979 300SD has a cluck when braking and I believe that these may be my problem.

A 79 SD has lower A-arms, not a control arm-guide rod arrangement. You might check the A-arm bushings.

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum

[engatwork]

thanks sixto for bringing that up. My experience has been with W123/126 cars.

moraine - the front end work is not very complicated - just more "physical" than say a valve adjustment. Go for it.

[WANT '71 280SEL]

I thought that w116's and w126's had the same suspension setup? Well, my w116 has a clunk on braking like you guys describe, what could it be then?
Thanks
David

[turbodiesel]

Out of curiosity, where is this shop?

[JHZR2]

I assume youre asking me... If so, I took it to Wilmington Motor Cars (renamed Mercedes-Benz of Wilmington). I really like Ditmire motorworks in Absecon, NJ, but that is 1.5 hrs away, so I dont always go there. R&K motors in Nwark, DE is a good place, the guy who owns it knows a lot about the w123 cars.

But I know that for the most part, Ill only have the dealer do alignments from now on...

Not sure if that info is of much use to you though...

JMH