First time poster here!!,

This looks like an excellent forum, lots of down and dirty tech questions and not a bunch of fluff, exactly what I have been looking for.

Now, a question please,

I just bought a 89 420 SEL with 125 K on the ticker and it has the slow tranny engagement syndrome, from park to drive and reverse, vice versa. Seems to shift well when underway and as far as I know it is still the original trans, got all the records with the car. I did a complete filter and fluid replacement, not a flush, drained the TC and all. It still is a bit slow to engage, probably needs a going thru, right? No trash in the pan, just a small amount of normal sludge. I have rebuilt a 380 SEL trans and have a ATC book which talks about bad piston seals but would really rather not get into another one, it was expensive, almost a grand in parts!!

Here is my real question, I have almost free access to a freshly rebuilt tranny out of a 85? 500 SEL Euro, would it work in my 420??

Thanks,

Chas

Yes, it would work.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

No, the 85 trans will not work in a 420. The 420 has a crank sensor on the back of the block and the trans has a cut out in the bell housing. Also, the netural safty switch is different but that can be swaped from one to the other. I guess you could cut out the bell housing to clear the crank sensor but you may weaken it.

I know the above because I have an 85 500 SEL euro engine in my 84 500SEL US car and an 89 420 trans. The 500 engine doesn't have a crank sensor in the back of the engine so the newer trans will work in the older car.

By the way, how much delay is there? The delay is also dependent on the idle speed. I don't know why, but the delay is much less at 500 RPM then it is at 1000 RPM.

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84 500 SEL (307,xxx miles)

Thanks for the replies!!

So, I guess the in 89 they went to a different ignition system that uses a flywheel sensor instead of a front pulley sensor? Or is the flywheel sensor for something else? I wouldn't want to hack away at the bellhousing either!!

It has about a five second delay after putting the selector into gear and the idle speed is right at a 1,000 rpm. My ATSG manual does have a section dealing with delayed engagement of the forward gears (but not reverse) caused by a poorly sealing B2 piston seal.

Sound like my problem? Probably not since I have the problem in forward and reverse, huh?

Chas

I guess I'll have to go look at an old trans as a quick look in the EPC shows even a 380SEL using transmission case part # 126 270 65 11. Same as a 560SEL or 420SEL or 500SEL. That number is an updated number so maybe they make the case to fit the new application and use it on the old. The sensor is not in the trans case.

BTW the crank sensor is at the flywheel on the 86 on cars but the earlier cars use an inductive pick-up in the distributor. The sensor on the front of the engine is for a diagnostic tool to pick up timing and plays no part in the running.

There is a bulletin that shows where to drill the intermediate plate to increase fill rate on those trannies to answer the original problem.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician