722.500 gearbox issues w124 coupe

[bh13coupe]

Guys

got a few issues on my 5 speed box. My engine has been out and put back in, got the car back today. Driving the car it engages D and R without issues but I have lost 5th gear (4th is ok) and the changes are uber jerky (way worse than when it was when it was cold). I can only assume this has happened as a result of the engine being disconnected from the box and reconnected. Could this be due to a loss of ATF or issues with the vacume lines? I am rubbish at understanding auto gearboxes.

Can anyone assist in explaining these symptoms? I intend to drop it in to be sorted next week but some background info to the faults would be appreciated.

 

[grober]

There are 2 major controls affecting shifts- the control pressure cable [ runs from throttle to gearbox] and the the vacuum connection from the engine inlet manifold . If the gearbox has been out both will need checked /adjusted for correct operation. If the gearbox was removed with the engine it may have lost fluid and need topped up. If I recall correctly 5th gear on that gearbox is engaged/controlled electrically unlike the rest of the gears which are switched hydraulically so look to the electrics for what might be the reason for your loss of 5th gear? My guess like you is you have a vacuum problem. You need someone who understands these particular gearboxes. For example if the vacuum line from the manifold to the ignition control unit is faulty/lost vacuum then you may lose 5th gear but that's only one possible cause.

 

[grober]

THINK I would start by checking all the vacuum lines especially the rubber connecting pipes --- Y junctions angles one way valves etc they can get brittle and split and leaks can remain undetected. Remember if one part of the vacuum system goes down the loss of vacuum effects all the connected systems.

 

[bh13coupe]

Thanks Greame

i appreciate your input. i will update the thread once my gearbox man has had a look.
Are there any other tell tale signs i can check to suggest the vacuum leak?

thanks

Paul

 

[Pottering]

I (Perth, Australia) agree with Graeme (Perth, Scotland) that electrics could be a reason for the 5th gear problem. I have the 722.503 gearbox which was playing up by skipping 4th and going from 3rd to 5th and only downshifting when you sunk the boot into the accelerator (kick down). After fearing a box out, big dollars scenario it turned out to be a poor connection to a solenoid that is involved in 5th and downshifts. Solenoid cleaned up and all was well. Maybe when your box was replaced this solenoid wasn't properly hooked up?

 

[bh13coupe]

I (Perth, Australia) agree with Graeme (Perth, Scotland) that electrics could be a reason for the 5th gear problem. I have the 722.503 gearbox which was playing up by skipping 4th and going from 3rd to 5th and only downshifting when you sunk the boot into the accelerator (kick down). After fearing a box out, big dollars scenario it turned out to be a poor connection to a solenoid that is involved in 5th and downshifts. Solenoid cleaned up and all was well. Maybe when your box was replaced this solenoid wasn't properly hooked up?

Its going in tomorrow for a check out. I am hoping its just an issue with the vacuum line popping off. The gearbox was serviced a month ago and was running perfectly untill the engine swap out. I know the 5 speed has a history of losing 4th gear, in this instance I dont have 5th.
I will post an update when the prognosis comes in.

thanks

 

[bh13coupe]

Not too happy chaps

The 4-5 shift is caused by the MAF being diconnected, I was aware and the new one is on order (bosch unit) the engine was running more smoothly with the MAF disconnected as the existing one was knackerd. I didnt know the 4-5 was electronic taking the information via the CPU which needed to know the load setting via the MAF.

however the Jerky shifts from 1-4th gears are caused by vacuum pipe missing from gearbox-to inlet manifold. I will be returning the car to be sorted ASAP. Looks like a School boy error and will be having words with my indie.
I will be updating when its all sorted.

 

[trapperjohn]

At least you are getting there. Glad to know its nearly sorted.

CHEERS

 

[grober]

Progress hopefully.

 

[300CE]

Cheers for the update Paul, hopefully the matter will be resolved shortly.

 

[mattc]

Compared to what the 5 speed boxes can cost if the problem was more serious I would call that a result.

Certainly worth mentioning to your usual garage but it could just have been a bad day..we all have them.

 

[bh13coupe]

Compared to what the 5 speed boxes can cost if the problem was more serious I would call that a result.

Certainly worth mentioning to your usual garage but it could just have been a bad day..we all have them.

In fairness, in 10 years they have never dropped the ball before with any of my cars. They are fixing the issue as we speak. I have a great relationship with them and wouldnt ever go elsewhere.

 

[bh13coupe]

Got the car back, all sorted. The car changes gear as smooth as a cashmere codpiece :bannana:

The vacuum line was the issue and the no 5th gear was due to the MAF disconnection.

Now for the sound system upgrade poss Jehnert and the Rust needs nipping in the bud.

Thanks for all your inputs.

 

[mattc]

you seem to know all together too much about cashmere and its uses!

Glad its all sorted.

 

[trapperjohn]

^What Matt said!

 

[Pottering]

Good result, always nice to hear of fixes that are straightforward and relatively low cost. This and other Merc forums seem inhabited by some who, when anyone raises a gearbox issue, immediately state with an apparently wise demeanor that a complete overhaul is required, generally at massive cost.

 

[colinspain]

I (Perth, Australia) agree with Graeme (Perth, Scotland) that electrics could be a reason for the 5th gear problem. I have the 722.503 gearbox which was playing up by skipping 4th and going from 3rd to 5th and only downshifting when you sunk the boot into the accelerator (kick down). After fearing a box out, big dollars scenario it turned out to be a poor connection to a solenoid that is involved in 5th and downshifts. Solenoid cleaned up and all was well. Maybe when your box was replaced this solenoid wasn't properly hooked up?

Hi, I have exactly the same problem as you had with my W124 - '94 E320 cabrio 5 spd auto. I am checking error codes and electric connections. OVP relay, control module, vacuum lines etc. Where is this solenoid you refer to, is it inside the gear box and if so can I just drop the gearbox pan to access it. Apprecaite any assistance. Colin