W124 E420 Transmission issue
 

Hi everyone.

Most of my activity here is regarding W123s but I am currently considering buying my friends W124 E420.

It has almost 100K miles, is in great shape and he usually gets everything taken care of right away - so I am confident about regular maintenance.

However; it has recently developed a transmission issue. I have searched this and other forums for a similar problem but it seems most folks have different issues with the 722.3/4

It currently shifts nicely through all gears; however once in top gear and doing 50mph+ I activate the kickdown, the engine seems to rev up but the transmission doesnt drop down for a second or more. There seems to be a substantial lag between kickdown activation (revs going up) and the transmission actually engaging. From the little driving I did in his car, I remember it shifting through all gears quite nicely and shifting down nicely as well. Just the kickdown thing is off. He had both the switch and the cable replaced not too long ago.

Any thoughts?

Based on our DIY, it should be an easy fix to replace the switch and get the kick down working properly. If that's the only issue you see, I would buy with confidence.

https://www.pelicanparts.com/techarticles/Mercedes-W124/116-ELEC-Replacing_Your_Kick_Down_Switch/116-ELEC-Replacing_Your_Kick_Down_Switch.htm

Thanks Dmitry

I guess everyone here has something against W124 V8s.....

My knowledge and repair/maintenance ability for my W123 has been greatly influenced by this and 2 other similar forums with a lot of the same people as contributors. So even their reluctance to answer (174 views / 1 response from a PP admin) would suggest staying away from this car and things similar?.... I am kind of torn, seller is my close friend - he wants me to have the car and I really want it but certain potential high mileage problems scare me.

While I did take a similar risk with my W123...somehow this scares me. I cant explain any of this.

So this is a 94/95 E420? How much does your friend want for the car?

You should PM member MAVA. I believe he's in the LA area. He rebuilds MB trannies for a living. Super good guy, very helpful. I'm sure he'll have some thoughts on what you're experiencing with this car.

My sig aside, there's nothing better than a V8 MB, lowered, and monos. Oh yeah.

I don't think it's that......it's more that the knowledge on this forum highly favors diesels of any vintage over the gas engines. The gas knowledge you do get tends to be for those that were sold in the 70s/80s alongside the 123's and 126's, again because of the diesel know-how for those cars!

While I don't have an answer to your question about the transmission (the kickdown switch or solenoid does sound like a possible issue), the big worry with the 90s cars (and the E420 in particular) is wiring harness problems (search this forum or over on BW about the biodegradable wiring). If you know for a fact that the harnesses (plural) have been replaced on this engine, it's worth a look. If they haven't, run far and run fast. Talk about a wallet bleeder!

100,000 on a 124 trans is a lot. I know that sounds crazy given what other makes will go, but the Mercedes transmissions seem to be pretty short lived. My 92 300TE only had 138,000 and the trans was shot. A rebuilt trans from Sun Valley was $1750 plus $250 shipping. I have been extremely pleased with the trans and I'm approaching 3000 miles since I swapped it out with absolutely NO issues. I will be performing regular fluid and filter changes, in hopes of keeping this one alive a little longer than the original, but figure the engine will give up before another 100,000.

My suggestion, being it is a friend, would be to do the kickdown switch change, with the understanding that if it does not fix the issue, the price of the car will have to be negotiated. If it fixes it, you get a nice car. If not, you need to plan on sinking about $2500 into a trans swap, cooler lines, new flex discs and trans mount as soon as you get the car. Ask me how I know.

And of course make sure there's enough ATF in it.

Thanks for all the input folks.

PARSHOOTS1, I totally agree. I have only seen one or two here with Monos. Driving my friends E420 even with the stock rims is still an awesome thing. Will definitely hit up MAVA. Thanks

Diseasel300, I hear you on the harness. His apparently has been replaced. Another friend is selling a mint looking 300CE with replaced wiring harness and a bunch of expensive work done but it sat for a while and now has a gas smell from the intake area. I m currently drooling over that as well.

MCallahan, I know of Sun Valley. At this point its more a last resort. If my friend gives me a super good deal on the car, I might consider shelling out that much money for transmission longevity. A simple fluid/filter change, vacuum adjustment should fix this issue. To be honest, it doesnt even bother me since I rarely ever need the kickdown in my arthritic 300D. The E420 has exponentially greater power and torque.

Yeah, simple fluid change and installing a new 2nd gear valve was supposed to fix mine, until I opened the filter and found pieces of the 2nd gear band in it.

I approach auto transmissions with a worst case scenario approach. By the time they start exhibiting signs of being ill, they are usually in need of a full rebuild to return them to full reliability.

goab:

With regards to downshifts, it may be helpful to understand that a 4-to-3 downshift will occur at part throttle, i.e., before the KD switch is activated, up to about 75MPH. To activate the KD requires completely depressing the throttle pedal.
If a part throttle downshift occurs, there will be an increase in RPM with very little increase in perceived acceleration. If, in fact, the transmission downshifted only part way (into a false neutral), there would be a very large, runaway, increase in RPM. If that occurred as the result of a full-throttle, kickdown, downshift, the RPM would increase so quickly that it would hit the rev-limiter. You would be quite aware of the sudden increase in engine noise, followed by the stumbling and misfiring caused by the rev-limiter.