300E Transmission problem

My son's 300E transmission has suddenly developed an unusual problem. It accelerates fine up to 40mph then suddenly downshifts and screams along at 5000rpm.
What gives?
Harry
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What year and mileage is your car? It sounds to me that it downshifted to 2nd gear... perhaps your valve body is bad...
What happen if you select your own gear? Such as using 2 and 3... will it hold?
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I asked my son and he said it holds in 3rd.
Is this a "replace the tranny" problem?
Harry

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88' with 130k

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This sound like valve body problem to me... however, alot of people want you to replace it. Many shop will try to rip you off by saying it will cost you $2500 to repair it.
Call up Silver Star Transmission listed on mbcoupes.com under part supplier. They are very friendly folks that I have spoke with... but didn't buy from them yet...
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I had the same problem. My reverse clutch had disentegrated and was clogging the valve body causing unrequested downshifts and sticking in gears. Fluid + Filter change helped for a while, but in my case, the clutch kept disentegrating and clogged it again. Try a fluid+filter change (make sure the valve body screens are cleaned too), if you don't go clear sailing, you've got something amiss in the transmission -- either a clogging or malfunctioning valve body.
Hope its just a valve body and not the clutches. Valve bodies are a quick swap. Otherwise yer in for a rebuild.
-Mike

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