Hard shift into Reverse - PeachParts Mercedes-Benz Forum

Biodiesel300TD · #1 03-14-2006, 07:33 PM

When I shift the 300TD in to reverse. It does two things.
1. It takes 2-3 second to engage.
2. It engages pretty hard. It actaully makes the back end jerk upward.
I thougth the jerking upward was the self leveling system but the height from the garage floor to the top of the wheel well doesn't change.

When I put the car into drive it actaully drops the rear a little but the engagement is smooth and only take 1-2 seconds.

Any suggestions for adjustments that can be made? Or is thie tranny just getting warn out?

Diesel Giant · #2 03-14-2006, 07:40 PM

Reverse shouls make the car go up, foward will make the rear end squat. As for the delay, the rear pump may be getting weak. With only a few seconds delay, I would not sweat it.

sailor15015 · #3 03-14-2006, 07:41 PM

Yeah I'd like to know what causes that as well because my wrecked '85 did that as well. I'm going to have the engine and tranny out in a few weeks and I'd like to get it fixed while the fixing's good.

Biodiesel300TD · #4 03-14-2006, 07:44 PM

Quote:

Originally Posted by Diesel Giant

Reverse shouls make the car go up, foward will make the rear end squat. As for the delay, the rear pump may be getting weak. With only a few seconds delay, I would not sweat it.

What is the rear pump? The suspension valve? If so I did a rebuild on that several months ago with no change.

It can be a pretty violent jerk into gear. Seems like it should be a little smoother anyway.

Diesel Giant · #5 03-14-2006, 07:50 PM

Another thought. Most cars that jerk into gear do that becasuse the valve body had varnish and gunk in the piston bores. They should have smooth actuation, but if they are gummy they can jerk.

Pete Burton · #6 03-14-2006, 07:52 PM

The rear (auxiliary) pump does not affect reverse engagement in any way. Delayed engagement of reverse is most likely caused by worn B3 friction plates, sometimes a piston seal issue and I'd suspect a valve body problem sort of rarely.

Biodiesel300TD · #7 03-14-2006, 07:52 PM

Quote:

Originally Posted by Diesel Giant

Another thought. Most cars that jerk into gear do that becasuse the valve body had varnish and gunk in the piston bores. They should have smooth actuation, but if they are gummy they can jerk.

Are you talking tranny now? Would a bottle of trans-x help out?

imdavid28 · #8 03-14-2006, 07:55 PM

Quote:

Originally Posted by sailor15015

Yeah I'd like to know what causes that as well because my wrecked '85 did that as well.

I second that motion. Mine jumps when you put it into reverse as well. I'm not talking about the car squating or stitting up in the rear, but kind of a delay then a "GO!" deal when putting it in "R" (in underground import streetracing, this is the racing gear)

Diesel Giant · #9 03-14-2006, 07:56 PM

Yes the tranny. You could try some trans x and see if it helps.

pawoSD · #10 03-14-2006, 07:56 PM

When my car is real cold it engages reverse quietly and smoothly within 3-4 seconds, when its real hot its also smooth, but at "above real cold" (non-freeway hotness) its jerky. I put it in reverse, and 3-4 seconds later, wham.

Its done that since I got the car 31,000miles/3 years ago so I don't worry about it. Plus, once its engaged, I can floor it, and if the engine's warm, I can squeal a rear tire for a couple seconds.

I'd not worry about what yours is doing. If reverse stops working, then you might want to look into it, thats what I'll be doing anyways.

Or 83 takes longer to go into either drive or reverse, but it does so very smoothly, and shifts are rock-firm, so the tranny is fine. These cars are all unique/have their own personalities, so no two act the same.

86560SEL · #11 03-15-2006, 01:07 AM

I have the EXACT same symptom as well on my 1985 380SE (gasoline engine). I am sure the tranny is basically the same set-up however and probably identical to the one in the 300SD.

When the transmission fluid is cold, it takes about 2-3 seconds to engage, but it is smooth. However, when it is warmed up and I place into reverse, it "slams" into reverse and still has the 2-3 second delay. Even worse when I am in drive and shift to reverse. Always pretty smooth when placed in drive however. Also, once in reverse, it works fine - no slippage.

As far as shifting, it is fine. I have the firm 1-2 shift (when cold), but it smooths out nicely when warmed up and the 2-3 and 3-4 shifts are smooth at any temperature, but not ultra smooth. I am told it is normal for these older Mercedes to have "noticeable" shifts. I am guessing mine is normal. It has not gotten any worse since I have owned it, so I have not fretted too much about it, but I cringe everytime it jerks into reverse, as I am concerned it is going to break something.

MBeige · #12 03-15-2006, 02:00 AM

I've heard that the differential pinion gear (?) could create an oval shape on the horizontal part and that can make that clunk and jerk into reverse. I too have a 2 second delay on the gear change (wagon too!) in addition to the jerk in reverse. Fluid needs to be replaced but have no time yet, it's black. If yours isn't black then something is wrong with the transmission internals.

pawoSD · #13 03-15-2006, 02:45 AM

Quote:

Originally Posted by MBeige

I've heard that the differential pinion gear (?) could create an oval shape on the horizontal part and that can make that clunk and jerk into reverse. I too have a 2 second delay on the gear change (wagon too!) in addition to the jerk in reverse. Fluid needs to be replaced but have no time yet, it's black. If yours isn't black then something is wrong with the transmission internals.

The differential on our 83 has a lot more play/wear in it than the one in my car, but the 83 engages forward and reverse very smoothly. Mine has a pretty tight differential, but clunks/slams it in. It doesn't bother me, I like it as it lets me know its ready to go