harsh 4-3 part throttle downshifts

I just spent several hours looking at the archives but was not able to find a well explained cure to my problem. My car is a 95 E320 that exhibits very harsh 4-3 shifts at slow speeds under part throttle applications.

For example if your slowing down to turn, say in the 25-40mph range and just accelerate moderately it will slam into 3rd gear. This happens when hot and I have no information on how to adjust anything but the kick-down cable, of which I shortened up quite a bit with no help.

Just FYI, I run Amsoil synthetic ATF in it if anyone thinks that might be contributing to the problem.

Thanks all,

Dale

If it is only the 4-3 shift that is harsh then I think you have an internal problem with your trans. Most trans have a vacuum adjustment point but that will control all shifts not just 1 specific shift. When was the last time the trans fluid and filter were changed?

The fluid is new and the old fluid was clean. I usually change it every 30k miles regardless for peace of mind. It has been doing this for quite some time so this is not a new thing with the car. 3-2 is also harsh but not quite as bad as the 4-3. All other shifts are smooth. It upshifts great at part or full throttle and downshifts fine at full throttle.

I was basically inquiring on more specifics to any adjustments that I may be able to make and just go from there to see if maybe I could smooth it out a bit.

By the way, I'm new to this forum but I couldn't help but notice all of the postings on synthetics and non-synthetic oils. The one thing I found missing was anyone doing an oil sample to back up their gut feelings on this topic. I've never done a sample on regular oil so I have no information to share with anyone on that but I have done many samples on synthetic oils, of which I only use, and they all come back great.

I ran 15W-50 mobil 1 in my car for 10k miles before I changed it and the sample on that came back perfect. I just recently sent a sample of Amsoil 10W-40 in with 10k miles on it and it too came back perfect. According to those samples I could have kept running the oil in the engine but I can't get passed the psychological aspect of it. It took me a long time just to get passed the 3k mile change. I don't ever see myself going more than 10k miles on the same oil in the future. Just my .02 cents.

I would be very interested to hear if anyone has done a sample on regular oil and what the results were. Who knows, maybe all of us die-hard synthetic fans are spending too much money on our oil!! I may even use my car as a guinea pig and try a sample on regular oil after 5k miles just to see what the results are.

Thanks to all and happy holidays!!!

Dale

[jbaj007]

Dale:

Is there a particular lab you use for the oil analysis report? Is it a mail deal like outpatient biopsy samples are done? Basic procedure? Thanks

Bruce

Bruce,

All of the samples I have sent were through Titan Labs. The only problem with them is the outrageous cost of the kits if you order them from their website. I've been able to find the kits at K-Marts and sometimes Wal-Marts for around $9.00, whereas they are $29.99 on their site. Go figure that one!!

If it comes to a point that I can't get them anymore I will use Amsoils. They are around $10.00 from any dealer and well worth it in my mind, especially if there are any concerns about your engine, trans. and rear-end.

The sample I just sent last month was mainly due to my concern of possibly having a bad head-gasket on my car. I recently have been having cooling problems on my 95 E320, and I wanted to rule out the head-gasket, of which the sample I sent in did. So as you can see, they can ease your mind a bit and help narrow the search down for a problem.

By the way, Arthur Dalton from this forum, helped me narrow the cooling problem down to indication. Come to find out I never had a real cooling problem, just a problem with my gauge!!

Dale

[mbdoc]

Maybe the harsh shift is a 4th to 2nd & that is common on all newer Benz transmissions with auto adjusting B1 band piston.

[jcyuhn]

I've noticed that bowden cable adjustment affects the quality of the 4-3 downshift in my cars. If the cable is set somewhat relaxed, for early upshifts, the downshift is correspondingly later. The throttle is open more, and you get a klunk and a bit of harshness on the downshift. Try adding a bit of tension to the bowden cable and see what happens.

Gents,

I hate to be to ignorant on the subject, but is the bowden cable the one that goes from the throttle linkage to the transmission? And if so what would be the appropriate tension on it? I checked mine and it has some slack in it.......

Thanks,

Dale

[jcyuhn]

Yes, that's the one. The specification is for no tension (but no slack either) with the throttle closed. There's a threaded adjuster you can use to tighten it up a little bit. See if that helps things.

Thank you sir, I will take up the slack in it. I'm sure that's what the problem is.

Dale