W124 88 230TE normal shifting and ASD question

[Amuso]

Hi all,

It has been a while since I drove a W124, and the other day I bought an old ambulance 230TE automatic. It needs a little bit of fixing, but hopefully nothing too bad I cant fix. It has 260.000 miles on it but seems well kept. Has been to the shop for a status check. Verdict: Needs new rear right wheel bearing, front pads, overhaul of the power steering and right rear shock replacement. And a few minor issues.

I am curious to find out how the transmission is supposed to work when fully functional.

With the added weight of a longer and higher 230TE (european ambulance edition) I think the car has a higher ratio rear diff. It is usually around 3000 RPM at about 55 mph. The transmission has an E and S mode (economy and sport I suspect).

It also seems to be fitted with ASD (anti-spin diff?) which seems to be defect as the light is always on. However it has been working a few times for about a minute after I start the car (ASD light would stay off). And it seemed the car had more power and when the rear wheels started to spin (winter over here now) a warning triangle flashed in the speedometer indicating wheel spin. This indicator does not work when the ASD light is lit and the wheels spin. Though I must mention it seems to accelerate just fine from a stand still for a 2.3 even with the ASD error. It just seemed more responsive when the ASD was working.

It engages D and R fine, smoothly and starts off just fine without any noticable slipping or flaring. Shifts rather fine into 2, 3 and 4th. Sometimes a bit rough shifting can be noticed, but nothing that I would say was harsh. It shifts quickly into 2nd (20mph perhaps) and 3rd at 30mph perhaps. It usually gets into 4th by the time I pass 40mph under light acceleration. Revs much higher and engages 4th at perhaps 50mph when I fully accelerate.

However it will not downshift from 4th above around 40mph. Under that speed it will downshift into 3rd if I accelerate hard. I havent checked how slow I have to go before it downshifts into 2nd. It seems the kickdown switch does not affect this at all. It may not even downshift from 4th if I do not accelerate hard below 40mph either.

Is this normal or do I need to check some adjustments? I read up a bit on the vacuum adjustments and bowden cable here, but wanted to verify normal behavior first. Or could the ASD cause the car to be in some sort of "fail-safe" mode where it reduces power and downshifts?

Also, if I go down a long hill and let of the accelerator and manually shifts into 3rd it does not engage 3rd unless I rev a bit. Same for 2nd if I go down slower the same hill. Is it supposed to engage 3rd and "engine brake" immediately when you select 3rd (or 2nd) ?

I havent checked the fluids yet, but I plan on later today. I do suspect it may be a bit low on ATF as the workshop mentioned an oil leak that could be from either the engine or transmission. They could not detect where without cleaning the engine and transmission. Engine oil pressure has been fine all the time though, so that is why I suspect there could be ATF leakage. Any known places/seals that starts to leak on these vehicles?

Thanks for any feedback!

[yal]

There is a test I posted a while back to get the ASD light to flash the code when its on. Here is the link...

http://www.peachparts.com/shopforum/showthread.php?t=142447&highlight=ASD

Also check the fluid in the diff. Good luck!

[Amuso]

Thanks yal!

I actually bookmarked that earlier today as I searched the forum and found that an excellent way to troubleshoot the system. I will have a look at the diff fluids as well. Thanks again for a great post!

[Amuso]

I pulled code 8 from the ASD light, bad magnetic switch or brake switch.

Any good tips on how to test these? And where is the "magnetic switch"? In the diff?

[yal]

Its usually the brake switch. Its right at the top of the brake pedal arm inside the cabin. Its cheap and easy to replace. On mine it was the plunger that was bad and when I pushed it I could tell that it had gone bad. I don't know where the magnetic switch is, sorry.

[brabus3.6]

I had the same problem and it was also the brake switch, £10 or so. The magnetic switch is on the diff I believe or at least at the back with the accumulator for the diff near the fuel pump. Its quite a pricey part too if I remember, hope it's not that.

I'll bet the ASD light doesn't come on until after you've pressed the brake, in which case its the switch.

[Amuso]

I will check the brake switch. Brake lights work ok though.

The ASD is usually lit the second the engine starts, but on occasion the light has stayed off, and the last time it did so until I pressed the brake pedal. Hopefully it is that simple I wont be able to get at the rear diff since I dont have any good lift ot stands to raise the car up on.

[Amuso]

Problem solved, and the problem was...

The connector from the diff sensor near the central locking unit was corroded really bad. Wires just came off by the touch of it. Resoldered the connections and now the ASD works. I haven't checked if the ASD light goes off in the lower dash since I removed the bulb, but the ASD warning triangle lights up when the rear wheels start to spin.

Also this may have solved another problem. The car would never downshift from 4th to 3rd if I moved the gear lever from D to 3 unless I tapped the gas. Now it does instantly. Could also have been fixed by me replacing the spring that pulls the gas lever towards the idle switch near the intake though...

[yal]

Thanks for reporting back Amuso! The more info on ASD we can help the forum archive the better!