Just discovered this forum... A treasure for sure!

I am hopelessly in love with my '89 420SEL. She has provided me with unbelievably reliable service for over 200,000 miles, and still handles like the day I purchased her for the most part. WHAT A MACHINE!!!

The tranny is starting to get uppity though. It chirps and squeals intermittantly at highway speeds and is starting to shift a little more roughly than usual. While it may be a simple bearing or seal that's needed, I'm curious about which Benz transmissions are compatible replacements (should it come to that.)

I frequently see decent 126 trannies up for auction on eBay and would like to know which would be "plug & play" with my 420. (I know there were improvements made to the 126 Benz transmissions in subsequent years, but don't know whether these units are backward compatible.)

I will probably wind up letting the Mercedes folks do the swap (if necessary, but I'd sure like to be somewhat educated before I go in there.)

Thanks to any of you in advance for taking a moment to provide some guidance!

The only ones that will directly bolt in are from 1986 thru 1991 V-8 cars like yours OR from the 560SEL or 560SL.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Before you "wind up letting the Mercedes folks" swap your
transmission for an ebay unit, have a look on this site for
good independent mechanics in your area. You might get
a better deal and find someone to do other repairs to your
car. If you really like the car and it is in good shape, it might
be worth rebuilding the transmission. The ebay units are
totally unknown units and you take your chances.
(Funny how most pulled parts have low miles, usually less
than 100K.)
If it hasn't been done, you should check or replace your
timing chain rails. (Standard warning with these engines.)

__________________
VR
1967 250SL

Thanks for the guidance and suggestions!

Timing chain, rails, steering linkages, radiator, belts, brakes, hoses, shocks, etc. all well maintained.

My rationale for turning more significant jobs over to "the Mercedes folks" is based on a few disappointing experiences I've had using recommended independent mechanics who supposedly "really know their Mercedes..." (No doubt there are some top notch pros out there, I'm just not interested in feeling like a damned guinea pig.)

I do tend to use these good local mechanics for procedures I generally understand. When it comes to more complex engine work (i.e. the transmission, timing chain), where my knowledge is limited, I feel less comfortable relying on these independents. "Knowledge is power," and when I haven't got the foggiest idea about what's being done to my car, I pay up for the piece of mind a Mercedes authorized mechanic gives me.

Regarding eBay, I'm a real believer in the feedback system. Specifically, I would never slap down more than a modest sum if the seller didn't present with impeccable feedback ratings. As I see it, I'm at least as safe buying equipment from someone on eBay with huge positive feedback scores as I would be trusting a local mechanic on the basis of a few neighbors' opinions. Maybe it's naive; but thus far, my experience buying auctioned replacement parts for my Benz has been VERY positive, and I've managed to maintain the car in like new condition without breaking the bank.

In any case, I genuinely appreciate your speedy responses to my inquiry. Many thanks!