1992 W124 300TE Auto box issues

[Lesharo]

On my new to me W124 Estate, reverse gear is lost after a run, when hot. I am fearing the worst but also looking for an answer.
As it may be that the gear box will have to come out for service/repair, Is it possible swap the four speed for a 5 speed auto box?

There was a great crowd in Poole, Dorset who serviced and repaired auto gearboxes but no longer trade. Can anyone advise such a company in the Dorset area?

I did find that the TQF level is high, perhaps the previous owner added oil thinking it was low, so my thought is, that with the additional oil in the box, cooling is reduced on shear volume of fluid thus causing a problem when selecting reverse. Any thoughts on that theory? I did notice a slight jump in changing gear at the near end of the run, possibly endorsing the heat dissipation theory. The Radiator does look like a recent replacement.

It will engage reverse when cold (after an overnight - stuck in the corner of the yard!)

 

[DREAMER NO2]

So remove some oil with a syringe .

 

[rayhennig]

Is it possible swap the four speed for a 5 speed auto box?

Doubtless possible but not a good idea unless you're a REALLY capable mechanic and electronics man.

You're not far from Horndean so speak to PCS about rebuilding your gearbox.

RayH

 

[mattkh]

I did notice a slight jump in changing gear at the near end of the run, possibly endorsing the heat dissipation theory.

Rethink the heat dissipation theory as the fluid expansion theory.

 

[Lesharo]

Chuck Berry
Author

Well to-day was 'play day'; as I was not under pressure to get things done (from 'er in doors)! I managed to clear a few "possible causes" The level in the gear box was dropped by approx. half a litre. In all honesty I am not that is the issue here, Yes reverse was going in but after quite a long delay and a little juddery but it did reverse. Having said that it was only a three to four mile run, whereas before it was around 25 miles. I will say the up and down changes are very smooth. So I am now convinced that as it is approaching 187k time has come for a major service on the auto box. While I am at it I will explore the possibilities of converting from four to five speed.

 

[LostKiwi]

Converting from a 4 speed to a 5 speed isn't straightforward.
There are also 2 five speed box families.
The later ones are 722.6 and electronic control of all gear selection - pretty much impossible to upgrade to.
Earlier 5 speeds are 722.5 family
These are essentially a fully hydraulic 4 speed 722.4 with an electronically controlled 5th gear.
To get this to work you'll need the electronic control and associated sensors and wiring (and sorry I don't know what they are - you'll probably need to do some serious googling).

 

[Lesharo]

Mmmmmm.... Had an idea it wasn't straight forward!
In comparison fitting an Automatic over/under drive to an American Big truck chevy was simples!
Still 'I have started so I'll fin....

 

[LostKiwi]

You may also need a new propshaft as I believe the 5 speed gearbox is longer than the 4 speed.

 

[Flyinspanner]

With your autobox, I think that maybe a complete fluid change may be the first thing to try.
ATF level is checked with the engine running (on most) check you have the correct method for yours overfilling can cause damage.

How third the fluid you dropped out look & smell?

check selector linkage - could maybe not be engaging properly

 

[rayhennig]

Your 300TE is very likely to have a 722.3 4-speed gearbox. The 722.5 is a 722.3 with the electronically controlled 5th gear. The 24 valve 300s and the 320s had the 722.5 box as an optional extra. I don't think the 12 valve 300s did but I may be wrong.

Your best course of action is to repair the 4 speed box. My 722.5 box was overhauled by Mackie Transmissions in Glasgow. They arranged shipment from and to PCS in Horndean. All seems well after about 60K Km.

Good luck.

RayH

 

[Lesharo]

With your autobox, I think that maybe a complete fluid change may be the first thing to try.
ATF level is checked with the engine running (on most) check you have the correct method for yours overfilling can cause damage.

How third the fluid you dropped out look & smell?

check selector linkage - could maybe not be engaging properly

As the existing fluid is very clean and a bright crimson, not smelling burnt, I can only assume at this point that the previous owner had already done the change and then decided to get rid of the car. The reverse gear selects fine and when the oil is cooler, up to around 3-5 miles, selects reverse OK but there is a shudder sometimes, other times it takes longer to to move. I discovered the lack of reverse after a 20 plus mile trip back home from the dealer. (obviously he denies any issues)

 

[rayhennig]

As the existing fluid is very clean and a bright crimson, not smelling burnt, I can only assume at this point that the previous owner had already done the change and then decided to get rid of the car. The reverse gear selects fine and when the oil is cooler, up to around 3-5 miles, selects reverse OK but there is a shudder sometimes, other times it takes longer to to move. I discovered the lack of reverse after a 20 plus mile trip back home from the dealer. (obviously he denies any issues)

In 2011, my reverse would disappear when the box was warm. Cold - reverse fine. Hot - reverse pretty good but sometimes a bit odd when reversing up a hill.

I had new fluid and filter installed by Haynes in Worthing and all was well until 2017 when the car and box went into PCS for overhaul. Reverse was still working fine.

So, you could try a filter and fluid change. The new fluid in mine was MB D3, not D2.

Recently we did a fluid and filter change from D2 to D3 and I feel that the changes are smoother than before.

RayH

 

[Lesharo]

Very Interesting Ray, thank you for that.
It was my first thought, fluid and filter change but when I saw the condition and colour of the TQF I assumed that was tried but what the .... for the sake of a pound or three it could be worth while. My car symptoms appear similar so I will try that.

 

[rayhennig]

My car symptoms appear similar so I will try that.

Don't forget that Haynes used a genuine MB filter and MB fluid. A bit more than a pound or three. Will you do it yourself?

 

[charlysays]

As the existing fluid is very clean and a bright crimson, not smelling burnt, I can only assume at this point that the previous owner had already done the change and then decided to get rid of the car. The reverse gear selects fine and when the oil is cooler, up to around 3-5 miles, selects reverse OK but there is a shudder sometimes, other times it takes longer to to move. I discovered the lack of reverse after a 20 plus mile trip back home from the dealer. (obviously he denies any issues)

If I were you, seeing as it works well otherwise and isn't burning up the fluid, drain a further 710ml out and replace with a bottle of lucas transmission fix. You may well find that does the trick. If not add another bottle and see how it goes as you can add up to two in larger transmissions. It's thick stuff so you might need to warm it to get it to go down the dipstick tube nicely.

I find additives can be very effective when the fault is partial or intermittent. I had a Mercedes C250 TD Sport auto with the electronic controlled 5spd which started not shifting into 5th and then 4th when cold. No codes indicated a mechanical issue. I'd already done a full fluid and filter change.
1 bottle of lucas stopped the problem recurring for 20k miles, a second bottle (with another fluid change) kept it going another 15k miles until I crashed the car.
Without 20 quids worth of lucas I could've ended up changing the box AND then crashing the car.

I've avoided changing any hydraulic tappets on my C250 TDs for years thanks to wynns hydraulic lifter treatment. Totally gets rid of the ticking for about 10k miles so it gets a can with every oil change.

My reliant scimitar with recent new PAS pump and rebuilt rack started losing fluid into the gators. two bottles of lucas PAS fix and it's still going fine 2 yrs later. As such if I'm faced with a big repair job for a non catastrophic failure especially intermittent issues I throw an additive, usually lucas, at it now.

 

[Lesharo]

As much as I want to fix this myself there is a first class chap locally that knows MB's, in particular W124 300TE, very well and he is not only going to do a filter and oil change on the gear box but go through all the checks of the complete car. In the long run it will save me a lot of time and anguish finding things that I may have missed; and least another pair of fresh eyes will be better than my old ones!

 

[rayhennig]

a filter and oil change

If he knows his MBs he should know that the torque converter must also be drained as it contains about half the fluid.

R

 

[Lesharo]

What is happening is that when cold or cool reverse is definitely selected; but after a hesitation as it gets hotter. All forward gears shift as would be expected although after the oil heats it can jolt very slightly. My local MB specialists are carrying out a power flush of the system next week, they say that rectifies many issues in the past (it is a MB recommended procedure and tool - I've been told). I will keep you all posted on the out come.

 

[rayhennig]

power flush of the system

I've never heard of that but I'm no gearbox expert. All I know is that a box/torque converter drain and filter change brought back reverse for about 6 years. As said before, the new fluid was MB D3 and the filter was MB. No cheapo stuff.

Incidentally, after my rebuild we did another drain and filter change (a few weeks ago) and my impression is that changes are now smoother. I think the box had D2 in it after the rebuild. We used D3 for MB.

RayH

 

[Lesharo]

Ray, thank you for your pointers. Since asking about this issue the car has been pushed into a corner of the workshop to make way for other pressing matters, but I must get on with it ... so here we go again!
Could you possibly direct me to a supplier of D3? I Have tried various MB suppliers and they only show Dexron III; is that the same? I have decided to go for a full oil change and cleaning of the pan and filter for starters. I have also been told that there is an 'O' ring or three on the Accumulator Switching-on Control valve and spring and accumulator switching-on piston, that could also be a source of trouble, so I need to source these before I start.