Tranny Slammed in Reverse at Highway Speed - PeachParts Mercedes-Benz Forum

i-osprey · #1 12-03-2007, 11:56 PM

OK, if you read my last thread you know that I had a wreck recently. When I did the motor and tranny mounts broke and it all shifted forward. Also in the process the shifter lever got bent out of shape.

For example, it will still roll when I have the lever all the way forward. I have to use the parking brake. Also, drive is actually engaged when lever is on Neutral. The lever is clearly bent but there may be another adjustment out of whack.

So, today I am cruising down the highway at about 65 mph when my dog situates himself against the lever that is already a millimeter from popping into reverse by virtue of its being out of adjustment/bent. He pops it into reverse and wheels lock up at that speed. I quickly put it into a forward or neutral gear and pull over.

Once the beating and cursing subsided I pulled away and to my amazement it worked. All gears forward and reverse work. However, I have noticed that the shifts are VERY soft like they are just grabbing enough to go. I haven't taken any serious hills yet but I fear it may slip when I do. I am more comfortable shifting manually but even then it seems that I am not far off from some engagement issues.

What do you all think happened internally and what do you recommend I do to prolong its life? Do you recommend the tranny fluid thickeners? I need to prolong its life mainly for financial reasons but I also don't want to risk being stranded when/if it fails.

Thanks

pawoSD · #2 12-04-2007, 12:30 AM

I'd say fluid/filter change ASAP, as you probably shaved some reverse clutch band material into the fluid in rather high quantity!

i-osprey · #3 12-04-2007, 12:41 AM

Will do. I did give the fluid the smell test and it smelled a bit crispier than usual.

Do you think that the original damage could have been contained to the reverse band?

pawoSD · #4 12-04-2007, 12:48 AM

I'm not an expert on the transmission, but I can't think of what else it'd damage in there besides that....none of the other clutches or bands are doing anything while in reverse as far as I know. Probably just did some significant wear (perhaps not all that much though) on the reverse band. The wear occurred as it engaged, that brief moment of serious friction, once its locked, there's not any more friction or wear on the clutch band, then the strain is transfered to the flex discs and tires. I'd probably check the flex discs too as thats a huge force to slam on them in the opposite direction. (They are built to withstand mostly clockwise/forward torque/force...so it may have damaged them with that sudden jolt....especially if they are older.)

PatricdeBoer · #5 12-04-2007, 12:49 AM

I have nightmares about that happening.

Cervan · #6 12-04-2007, 12:51 AM

one of the reasons i love mercedes, you tell me one other car that you shift into reverse doing highway speeds and can still come out driveable.

pawoSD · #7 12-04-2007, 12:55 AM

Quote:

Originally Posted by Cervan

one of the reasons i love mercedes, you tell me one other car that you shift into reverse doing highway speeds and can still come out driveable.

So true.

I sit next to a guy in my math course who is a tranny rebuilder....maybe I will tell him about it.

pawoSD · #8 12-04-2007, 12:58 AM

Quote:

Originally Posted by PatricdeBoer

I have nightmares about that happening.

As do I....I am always paranoid when someone else is in the passenger seat and is moving around/adjusting their legs etc....one good bump to that shifter....it usually results in my anally asking them to not bump it. To which they think I am insane. (perhaps, but its out of love for the car!

)

i-osprey · #9 12-04-2007, 02:12 AM

Quote:

Originally Posted by Cervan

one of the reasons i love mercedes, you tell me one other car that you shift into reverse doing highway speeds and can still come out driveable.

I totally agree. I have never heard of another car making it out of something like this. In fact, I was resigned to the fact that my $1500 car had just suddenly became much more expensive before I put it in gear and took off.

I should have known better though. My first MB diesel was a 1982 240D with 260K on it. I lived in Kansas at the time and was completely ignorant about what might be causing my starting difficulties so I just wore out a starter. Once it was so cold, probably about 0F, it just wouldn't start no matter what. I started reading the manual and it showed that you could pull-start it if necessary. My dad hooked it up to his pickup and pulled me about 45 mph the first time. No start at 45 but the next time at 55 it fired up. I just had it in neutral until target speed was achieved and then put it into gear, seriously. It was prescribed in the manual that way. I couldn't believe it.

I have formally decided to just rebuild this car ad infinitum rather than buy something less exceptional. I won't rule out buying something in addition to this car but I will never replace this one short of a catastrophic loss.

i-osprey · #10 12-04-2007, 02:55 AM

Quote:

Originally Posted by pawoSD

I'm not an expert on the transmission, but I can't think of what else it'd damage in there besides that....none of the other clutches or bands are doing anything while in reverse as far as I know. Probably just did some significant wear (perhaps not all that much though) on the reverse band. The wear occurred as it engaged, that brief moment of serious friction, once its locked, there's not any more friction or wear on the clutch band, then the strain is transfered to the flex discs and tires. I'd probably check the flex discs too as thats a huge force to slam on them in the opposite direction. (They are built to withstand mostly clockwise/forward torque/force...so it may have damaged them with that sudden jolt....especially if they are older.)

Flex discs are on the way. I ordered them about a week ago and they definitely needed to be replaced before this latest escapade.

I will have to be very careful until they get here.

zeet · #11 12-04-2007, 02:59 AM

Quote:

Originally Posted by Cervan

one of the reasons i love mercedes, you tell me one other car that you shift into reverse doing highway speeds and can still come out driveable.

I've been in a mid-90s Mitsubishi when it was shifted into both Reverse, and Park, at about 40MPH. Reverse stopped us very quickly with locked wheels. Park made a horrible tearing noise. After both, the car drove fine, though I only followed it for a month.

stcbenz83 · #12 12-04-2007, 03:37 AM

Did that to my dads Caravan once going about 45. Made a clicking noise and shifted it back into drive and it died. Pulled over and put it in park and started it up. Had no problem with it and no clue why it died. Funny that the trans didn't blow up, being a Chrysler and all

i-osprey · #13 12-04-2007, 03:43 AM

Those last two posts do surprise me.

I know of an early 90's Nissan Sentra that was shifted into reverse or park at highway speed and it was toast. I also was in a mid 80's Chevy pickup that was shifted into park/reverse at highway speed and it blew transmission fluid all over the highway and the engine compartment. It was toast too.

Either way I am encouraged that apparently I will be able to continue to drive my car.

alamostation · #14 12-04-2007, 07:03 AM

Quote:

Originally Posted by Cervan

one of the reasons i love mercedes, you tell me one other car that you shift into reverse doing highway speeds and can still come out driveable.

It can be the sign of a good car or a bad car.

I did it 34 years ago in my '32 Plymouth sedan hot rod with a Chevy 283 and a Powerglide in it. That Powerglide had so much slippage it could probably roll backwards while in drive if there had been a hill in the Detroit area.

I will save you a long story about how it happened and at what speed, but the skid marks must still be there on West Jefferson in Wyandotte between the old Firestone factory and the Pennwalt cat pee plant.

After it sent a huge flame out of the carburetor, it started up immediately and ran better than ever.

LUVMBDiesels · #15 12-04-2007, 08:06 AM

Quote:

Originally Posted by Cervan

one of the reasons i love mercedes, you tell me one other car that you shift into reverse doing highway speeds and can still come out driveable.

A moron friend of my ex-wife did just that, but on purpose!

We were driving down the highway in Philly when he missed his exit. He then slammed his Oldsmobile Delta 88 (the front wheel drive version) into 'R' and hit the gas. The car went BANG BANG BANG and bucked as the tires smoked. He reversed - on the driving lane- back to the exit, hit 'D' while we were going backwards -BANG BANG BANG and we shot up the exit ramp. My heart was actually outside my body at this point!

The car survived that experience, but he told me that "they don't make cars good anymore and that he had to trade them in every year"

Oh he also liked to run the right wheels up the curb at 55 MPH.
I pity the poor sucker who biught THAT car at the used car lot!