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1995 SL600, 1983 380SL, 1987 560SEL, 1974 Lotus Europa TwinCam Special
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42 Posts
Discussion Starter #1
Talked to a transmission shop that is doing a trans replacement on my SL600 about a trans tuneup on my 380SL with about 200K miles on it. Not exactly sure when this was last done but it's been a while. No real problems with it but thought it probably should have filter/fluid replaced. The shop owner said that he wouldn't do anything until problems arise. In his experience (not a Benz specialist by any means) high mileage cars with new filter/fluid replacement can cause big problems stirring up stuff left by all miles of driving. Any thoughts???

Thanks

Joe
 

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'85 380SL (155Kmiles), '82 240D stick, '80 300SD, '77 240D, '89 BMW 535i, 3 VW Diesels, 2 Triumphs
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1,553 Posts
Change it, if it hasn't been done in 5 years. I'm not sure how you could "shake up" stuff in a transmission by just draining the torque converter ( which is normally spinning ) or draining the pan ( which constantly has fluid circulating in it). I wouldn't be "power flushing " it , or any transmission, for that matter...
 

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1978 280slc
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3,203 Posts
I think you are more likely to burn up a transmission by not changing the fluid than by changing it. The whole if your transmission isn't giving you any issues don't maintain it doesn't ring true. Changing the fluid and filter will also give you a good indication of the condition of the transmission also. How would a tranmission with a partially blocked filter and dirty fluid perform as well as one with fresh fluid and filter?
 

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3,783 Posts
I have tried to get 3 different shops change the fluid and filter on 3 different cars, all around 150k with no knowledge of when it had been done last, and none of them would do it.... I think the problem is that when they perform a flush, (most shops will not simply change the fluid and filter,) they use a very strong detergent that can cause deposits of tiny bits of brake bands, clutch discs, and pieces of metal in crannies of the trans to become loose, but not dislodge, and then they will dislodge randomly and wreak havoc. I don't think it could hurt to just drain it and change the filter, but I am far from an expert. Then again, I have heard of plenty of people going to change the fluid and filter and having the transmission completely fail afterwards... Personally I wouldn't touch it unless you are having problems or the fluid looks dirty or burnt.
 

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87 560SL
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292 Posts
I agree, a 'flush' is not a good idea on an old trans. However a drain and filter change is definitely a good thing. Trans fluid deteriorates with age.
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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6,050 Posts
On my cars, if the fluid is dirty and smells of varnish, I disconnect a tranny coolant line, start and drain about 1 qt, refill and repeat untill clean. Would never do a power flush on an old unit (maybe on the ex).
 

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'71 250, '78 450SLC 5.0, '78 450SL, '81 380SLC 5.6, '89 260E, '15 Kia Sorento
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5,269 Posts
Has anyone had the BG service done and does that change your opinion or would that fall under the "power flush" heading?
 

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1978 450SL--117K
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1,374 Posts
I have tried to get 3 different shops change the fluid and filter on 3 different cars, all around 150k with no knowledge of when it had been done last, and none of them would do it.... I think the problem is that when they perform a flush, (most shops will not simply change the fluid and filter,) they use a very strong detergent that can cause deposits of tiny bits of brake bands, clutch discs, and pieces of metal in crannies of the trans to become loose, but not dislodge, and then they will dislodge randomly and wreak havoc. I don't think it could hurt to just drain it and change the filter, but I am far from an expert. Then again, I have heard of plenty of people going to change the fluid and filter and having the transmission completely fail afterwards... Personally I wouldn't touch it unless you are having problems or the fluid looks dirty or burnt.
About seven years ago a retired GM engineer (helped develop the modern Corvette, which is no slouch) told me never to allow anyone, including the Cadillac dealership which sold me my Cadillac, to flush a transmission. He told me that the flush usually runs in the opposite direction from that which the tranny fluid flows--that it will almost certainly dislodge parts like o-rings and what not.

All any tranny needs is a fluid drain, new filter and fresh fluid. It's all I have ever done anyway and I have never "dropped" a transmission. Well, not a automatic transmission anyway. Broke a few teeth on manuals..........
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,341 Posts
I have never had a transmission fail due to a simple fluid and filter change nor have I heard of this from friends that have done it. Any shop that wants to flush and not just change the fluid is just trying to get deeper into your pocket.
 

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1989 560 SL - Signal Red & Palomino; 2011 C-300 - Black on Black 4MATIC
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I had a fairly detailed conversation with the shop that did mine, and totally agree with the practice of a simple fluid change. From what I understand, there are two major reasons for faillure. The primary is heat, which fresh fluids and a fresh filter are very helpful in fighting. The second is aging rubber parts, etc. which can occur regardless of miles, etc. - time is really the enemy in that situation. Sometimes these can be addressed sans a full on rebuild, but that depends on the car. It is routine for this shop to recomend the simple change vs. flush depending on the age and miles of a car.

I would seek out a shop willing to do the simple change. I would be suspicious of the ability of a trans shop that is unwilling to do that, IMHO.
 

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1984 500SL 000760
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509 Posts
I worked at a auto shop that had a trans shop in it and the guy who ran the tranmission side would not service high mileage cars with a flush, he claimed also that it would cause the trans to fail shortly after if the fluid had never been changed before an it had over 100K miles, he would only reccomend a fluid/filter change, never a power flush on high mileage cars with unknown service history.
 
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