144k my first trans delay/slow shift
03-01-2023, 09:22 PM
#1
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Join Date: 10-31-2008
Location: Exton, PA
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144k my first trans delay/slow shift
Hello I am a Mercedes tech with access to the shop but need some experienced advice with my 09 LS 144k. On cold start(always remote start for a few mins), takeoff is fine but first shift hung to 3100 rpm before soft shift….today was a little different with feeling like a very slow shift with a alarming pause in acceleration with ramped up engagement of next gear finally…after the first 2 accelerations it feels normal and won’t happen again. I have no codes with a basic code reader. Happening at about 18-25mph. Just did the cars 2nd trans service a few weeks ago. I’m willing to shotgun all the shift solenoids if this sound like a possibility, thanks.
03-01-2023, 09:43 PM
#3
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Join Date: 10-31-2008
Location: Exton, PA
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Just means fluid, filter, gasket, tube insert, magnet/pan cleaning, and level setting with vehicle running via draining at fluid level port. I did the first one at 75k cause of a clumsy shift sometimes, it fixed that. People who rebuild these recommend 40k changes, seems a bit too frequent to me, I’d say every 60k-80k.
03-02-2023, 08:13 AM
#4
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The people that made the transmissions say "maintenance free" unless used for livery. I think the people that rebuild them are looking for work or, they live in the last century. The number of 4T45 trannys that need rebuilding is pretty low and limited to very high mileage.
For hard shifting I would look at deteriorating VVT valves, the oil screens can get clogged before throwing a code or the code may stay pending and go away before setting the light. Then take the valve cover off and inspect the timing chain, any slack is bad.
The 4T45 is rarely to blame for hard shifting. More likely computers protecting them from something else or pins on connectors have been bent or pushed out.
The solenoid codes have to occur twice in a drive cycle to light the CEL, but if one is bad it will affect 2 gears; the 1-2 solenoid kills 1st and 4th, 2-3 solenoid kills 1st and second.
So, if you know how to get live transmission data you could figure out if one of them is a problem.
For hard shifting I would look at deteriorating VVT valves, the oil screens can get clogged before throwing a code or the code may stay pending and go away before setting the light. Then take the valve cover off and inspect the timing chain, any slack is bad.
The 4T45 is rarely to blame for hard shifting. More likely computers protecting them from something else or pins on connectors have been bent or pushed out.
The solenoid codes have to occur twice in a drive cycle to light the CEL, but if one is bad it will affect 2 gears; the 1-2 solenoid kills 1st and 4th, 2-3 solenoid kills 1st and second.
So, if you know how to get live transmission data you could figure out if one of them is a problem.
03-03-2023, 08:00 AM
#5
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Join Date: 10-31-2008
Location: Exton, PA
Posts: 23
Yesterday morning 44 deg F, no trans issue, today 37 deg and delayed shift again. I would say it is likely a temperature related issue. Also does anyone know if our cars start off in 1st or 2nd gear?
03-03-2023, 08:12 AM
#7
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Location: Davison MI
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Unless there is something wrong it should always start out in first gear.
03-25-2023, 05:30 PM
#9
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Join Date: 10-31-2008
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Well things might get interesting, drove my car from PA to NC today, NC to FL tomorrow…stopped at a gas station 3 hours into drive and driving away 1st gear hung to 3k then I had no engagement rolling onto the on ramp, very bad, I kept Erving it and eventually got the shift….so not from cold weather….seems to be on any restart of my car. In further development the engine seemed to studder more than usual, I might not be going home in the same car, might have to ditch it lol