W 140 (1994/5) with 4 Speed gearbox No Reverse When Hot, and Power Steering Heavy at slow speed.

[MercyMerc]

HI All once again. Having bought a w140 a fortnight ago. You have all been most helpful in guiding me through a process there; Thnak You.

I am just about to buy another W140 (1994/5 car) with NO REVERSE gear when hot, but it is there when COLD.
Is this likely to be the solenoid?. Someone told me it would be the clutches at the front of the gearbox (4 speed), and easy to replace when the box is out, i.e., just pull off the front cover and drop them in. Does anyone have experience with this problem and the fix.

Also the Power Steering seems fine when over about 1500rpm, and I thought htis might be a pump issue rather than the Steering Box. Any expereinces with this would be gratefully received. Thanks in Advance

 

[gsxr]

I am just about to buy another W140 (1994/5 car) with NO REVERSE gear when hot, but it is there when COLD.

That's odd. Not sure I've heard of this specific scenario, and it definitely isn't common.

How long is the delay when engaging reverse? Up to 1 second (2 tops) is normal. More than 2 seconds indicates the reverse clutch pack is probably worn out.

Someone told me it would be the clutches at the front of the gearbox (4 speed), and easy to replace when the box is out, i.e., just pull off the front cover and drop them in. Does anyone have experience with this problem and the fix.

Replacing the reverse clutches is not exactly easy, but it's not rocket surgery either. It's also not as simple as "just pull off the front cover and drop them in". Once the transmission is out of the car you can remove the front cover/pump assembly and K1 drum, then extract the reverse clutch pack for inspection / replacement. You should absolutely, without question, replace EVERY SINGLE external seal on the transmission while it's apart - and inspect the K1 clutches as well, along with band B1. All these are accessible without tearing deep inside (K2 and B2 require substantially more disassembly). Once the transmission is on your workbench, the job is DIY'able if you have basic tools, can read the FSM, and follow some YouTube videos.

Also the Power Steering seems fine when over about 1500rpm, and I thought htis might be a pump issue rather than the Steering Box. Any expereinces with this would be gratefully received. Thanks in Advance

Not sure what would cause low-speed steering issues. Are you sure it's a power assist issue and not alignment? Is it so heavy it feels like manual steering? If so, that could be low pressure from the pump.

 

[MercyMerc]

Ah, Oh, OOo, , Hmmm!
Well the steering box feels normal when driving and new tyres and an alighnment was done. Not so heavy as no pump pressure. The problem apparently started immediately after the then owner picked up the car after the tyres.

Re the gearbox, whilst I am not a rocket scientist, I am definately intimidated by a full gearbox disassembly. Is this box fitted to other models? and which ones? I am thinking a second hand box might be my economic solution.

Apprecite your advice, cheers, Mercy

 

[gsxr]

Re the gearbox, whilst I am not a rocket scientist, I am definately intimidated by a full gearbox disassembly.

To clarify... it's not a full gearbox disassembly to replace the reverse clutches, B1 band, or K1 clutches. Just need to remove the front cover/pump assembly to access these bits. It's advanced DIY, but still DIY'able. Taking the front pump out of the front cover to replace the O-ring requires some creativity with fabricating tools/clamps, as some YouTube videos will show.

Is this box fitted to other models? and which ones? I am thinking a second hand box might be my economic solution.

You didn't specify the exact 140 chassis/engine combination, but the 4-speed boxes used on early 140 are all 722.3 and there are usually plenty of donors available. However, any used transmission is a gamble and you will need to do the same disassembly / inspection / seal replacement as described above anyway!

 

[LWB250]

I do know that some models of the W140 had a feature known as "progressive steering" or something to that effect - I don't recall the exact name. Essentially, it provided additional power assist at low speeds to make the car easier to steer. If the controller or its shuttle valve in the steering gear act up, it can cause the steering issue you mentioned. You would either have "juddering" at low speeds as you turned the wheel or nothing at all (amazing how heavy that steering is without assist?) I'm pretty sure it's facelift models, but check your option list to see.

The guys at C&M in Las Vegas that rebuild steering gears are the best and most knowledgable that I've found in the 30+ years I've worked on Mercedes. I realize you're Down Under, but if you can't find anyone there I know they'll most likely do it. That, or they may know who their equals are in Australia.

Good luck!

Dan

 

[emerydc8]

Discount Tire once jacked up my car by putting a jack under the steering damper and I didn’t notice it until the next time I was under the car. It might be worth a visual inspection if you haven’t done so.