I have a 78 420sel with 190k and I have put about 15k miles on it. The question is should I change the transmission fluid or not. I have gotten two distinct opionions about the subject. I have no knowledge about the service history on this car prior to owning it. The tranny is fine. Smooth shifting - no complaints. I would like to keep it that way. Some say if I change the fluid, the new fluid might cause the transmission to start having problems. Apparently the new fluid might "wash off the good stuff" that is allowing the transmission to work. But on the otherhand, not servicing the transmission cant be any good on it either. I actually had one tyranny shop refuse to service it cuz they were afraid that it would quit working. I also had a mechanic at the local MB shop say something similar. So it seems I am between a rock and a hard place.

It seems to me that if the tranny is on its last leg, changing the fluid might hasten its death which is inevitable anyway. So since I plan on keeping the car, I should go ahead and swallow the pill and change the fluid and live with the consequences. Does anyone have any experience with this senario? What are your recommendations?

Thanks.

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

I too have heard that before.

I'm interested to know about this too.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon

yes I've heard that before. And I've talked to some friends that are tranny rebuilders about that topic. and they tell me that staement is a scare tactic used by tranny shops that advertise fluid and filter change for a very low price to get you in to the door,and then when they open up your pan, Gasp....look at all the metal shavings down in the oil pan oh theres something wrong internally we have to take the tranny apart and see what broke . and if you reply well lets just change the fluid for now .they reply we can't if we put new fluid in your tranny it will eat all the varnish off of the clutches and we will be resposible.and they then take your old fluid that was put into a clean catch pan before they started your oil change and put it back in and make you pay $20.00 or so dollors for there new gasket that they installed for you. So go ahead change your fluid and filter and remember this you can never go wrong doing somthing positive like changeing oil.and theres nothing coorsive about tranny fluid.

Well if you don't service it you are guaranteed to have problems. MB builds really good transmissions. They accept all kinds of abuse. The chances of causing a malfunction from servicing is about the same as the death risk from having a tooth filled.

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

When I last asked my mechanic to change my tranny fluid, the first question he asked me was whether or not it had been changed regularly, and if it wasn't (which it was) he would have suggested I not do it.

He said he had a recent incident involving changing trans fluid in an MB with high miles on it that hadn't been changed in a while, and after re-filling new fluid in, it wouldn't even back out of the garage. I agree, however, if you get to this point, it's probably going to die sooner or later regardless.

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2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey

SOLD:
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino

I drive 84 Ford f-150 with 200K + daily as a work truck, haul heavy lods and trailers. I change the tranny fluid twice a year. So far so good. As with most people auto trans are somewhat of a mystery to me. I recently talked with a drinking buddy of mine who owns a trans shop and he explained the theory to me and invited me to come and se some of them broken down. He finds them to be very simple in fact. I think many of our worries are out of ignorange. How many of use really know how trannies work? I am going to take him up on his offer (case of beer in hand)

WOW what a cool site. I almost want to stay home today. Very good explanations and animations. Thanks!

I agree with steve019. I think the transmission shroud of mystery is a plot from MB and the few brave souls who have ventured into unknown territory - The tranny shops that rebuild MB trannys. I would tackle one given the opportunity. Everything about MB cars that I have worked on so far has proven to be easilly repairable. And I believe that is true for the transmissions as well. The biggest problem is the lack of information on the subject. Now the cost of the parts -- well -- thats another chapter.

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

I'm not a pro, but I've been into a few auto trannys. I think the most ambitious job I did was to swap the guts from a big block Ford C6 into a small block C6 case (I had a 302 in a F100 that died and I bought the big block trans at the junkyard for something like $40).

Once you're in there, it's no big deal, but it does take a lot of time. Everything has to stay in order and you have to keep it very clean. If there's a problem, sometimes you can spot it easily (broken o-ring, burned clutch plate, etc. Other times though, it could be a blocked passage in the valve body, a leaking o-ring, etc. The risk in doing it yourself is that you'll take it all apart and won't find anything. Then what do you do? Put it all back and you've wasted your time? Bring it to a trans shop and confess that you've been into it (now you're REALLY gonna pay).

Not to mention that you need some special tools to take out the gearsets.

I think shops face these same dilemmas and that's why you don't see a lot of auto trannys being repaired. They just completely rebuild it, and then warrantee the repair, or they don't want to work on it at all.

What are the other perspectives out there?

Getting back to the original post - I would change the fluid.

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D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.