1991 300sl transmission weirdness

86Topless

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1991 300SL
My '91 300sl has developed a weird issue with the transmission. Seeking the genius of others.
Car has run fine for 181,000 miles.
Last week, the transmission won't downshift by itself. I can manually shift it, but left in drive, it stays in top gear.
When starting out from a stop, it also has no power. Seems to be starting in top gear as well. Again, I can manually shift it into low and it runs fine and I can manually upshift it... same thing.
It's probably something simple (I hope).
Any suggestions.

Also, about a year ago, it developed a weird downshift issue. When going around a corner at lower speeds, the engine would race when accelerating, like the trans had shifted into neutral. Back off and let it settle, all is fine.

Hope I don't need to find a new or rebuilt tranny.
 

teddycatkin

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W107-SL W124-220te W123-230e W201 2.0
My '91 300sl has developed a weird issue with the transmission. Seeking the genius of others.
Car has run fine for 181,000 miles.
Last week, the transmission won't downshift by itself. I can manually shift it, but left in drive, it stays in top gear.
When starting out from a stop, it also has no power. Seems to be starting in top gear as well. Again, I can manually shift it into low and it runs fine and I can manually upshift it... same thing.
It's probably something simple (I hope).
Any suggestions.

Also, about a year ago, it developed a weird downshift issue. When going around a corner at lower speeds, the engine would race when accelerating, like the trans had shifted into neutral. Back off and let it settle, all is fine.

Hope I don't need to find a new or rebuilt tranny.

1st thing to do is check fluid level ?
 

rapide

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1997 E230 (no rust) 2016 volvo xc60 r/design. se. lux. nav.
dodgy shifting etc

the flaring up in a corner is low fluid level. on these 4 speed boxes its all hydraulic no electronics and they will go on for ever with a proper service and proper driving ie; no kick downs at every straight road! it sounds as though it has picked up some muck in the valve block from dirty oil and cocked up the shift pattern, they are easy to service, buy a filter and sump gasket from mercs ( pattern ones dont fit well, no cheaper) buy ( get the quantity from a haynes manual or on here about 7 ltrs) of dexron ATF,ordinary auto box fluid nothing special, drain box and torque convertor it has a drain plug, drop sump replace filter refit fill it up and you might get away with it , if not it will need the valve block cleaning out by a good indie mechanic who knows his stuff ! the fluid is cheap and you can reuse the filter and gasket if the first option doesnt work so give that try first, i have done them myself over the years but to old to get under anymore! all the best!
 
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television

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2002 SL500, 216 CL500, all fully loaded
Yes another saying low on fluid :D
 
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86Topless

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transmission weirdness (continued)

the flaring up in a corner is low fluid level. on these 4 speed boxes its all hydraulic no electronics and they will go on for ever with a proper service and proper driving ie; no kick downs at every straight road! it sounds as though it has picked up some muck in the valve block from dirty oil and cocked up the shift pattern, they are easy to service, buy a filter and sump gasket from mercs ( pattern ones dont fit well, no cheaper) buy ( get the quantity from a haynes manual or on here about 7 ltrs) of dexron ATF,ordinary auto box fluid nothing special, drain box and torque convertor it has a drain plug, drop sump replace filter refit fill it up and you might get away with it , if not it will need the valve block cleaning out by a good indie mechanic who knows his stuff ! the fluid is cheap and you can reuse the filter and gasket if the first option doesnt work so give that try first, i have done them myself over the years but to old to get under anymore! all the best!

OK,

Had it to a transmission repair shop. He couldn't find any obvious issues, but thought it might be a catalytic converter problem. Took it to a muffler shop and we cut off the 2 original Mercedes cats and replaced with a set of high perf. aftermarket cats. Both old cats were pretty well shot to hell.
Still no joy on the transmission issue. Tranny shop suggested I take it to a Mercedes specialist, so.......
He diagnosed it as a possible clogged filter (even after the trans guy said no way).... so I had his drop the pan, replaced the filter and all new fluid.
STILL no joy.
Trans shifts fine in manual mode. Starts in 2nd (1st when cold) and can be shifted manually and it works fine. But put it in drive and it starts in 2nd and immediately shifts up to 3rd then 4th (by 20mph) and will not downshift at all until you come to a stop.
I think it's time to start thinking about a new tranny.
Rebuild the one I have at the trans shop, or find a good used one, or bite the bullet and buy a rebuilt one and have the trans shop replace it?
Ideas?

BTW. car has 181k miles on it. Uses no oil (other than a persistent tiny leak). Body is still perfect. 20+ MPG. Everything still works (except for a top cylinder tonneau cover latch leak).

I know it's probably not worth throwing $1000 or more into it, but I hate the idea of scrapping it.

Thanks for all the help.
 

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