W123 4 Speed Manual Gearboxes - How easy / cheap to repair?

[pastelgrey300D]

Hi folks, just a few question about 4 speed manual gearboxes for a W123:
- Is the 4 speed gearbox the same on petrol and diesel cars?
- Can you get brand new bits (bearings, synchros etc - maybe from our forum sponsor?) or is it a case of finding another gearbox and doing a 'wrecker rebuild'
- How much time / effort is required to say, replace a synchro and has anyone had to do repairs or something similar before?

I know most of us have slushboxes but I'm sure it's been done before! Thanks guys! :lol:

[4heckssake]

I've got a 5 speed box (pommy import) in the 230e I got from Hendrik.
It's problem free at the moment and I'm not sure if they give any grief normally.
It's so nice to drive I was dreaming about getting a manual 300D and turning it into a ute. 8)

[CraigB]

I reckon Hendrik might know the answer to this. I think there was a diesel 4spd at upullit and Hendrik said it wouldn't fit a M110 I think the question was and maybe not the petrol either?

For the other questions, someone locally priced bits from various suppliers and it was going to cost $1500 or so in bits. Depends what is wrong though. If it was bearings then I would guess a local bearing place could supply the right size and it would be relatively cheap. Synchros are another matter though, but probably just one or two needed. I know on an Alfa you can swap between the gears and sometimes saving buying one, can't remember but something like swap the 2nd with the 5th where it doesn't matter so much and just buy a new 1st.

Also just remember other things might be needed like pedal box, clutch hydraulics, flywheel, clutch, possibly cross member and tailshaft. Also you are supposed to dismantle the engine and balance the crank with the flywheel like they did in the factory, but I haven't seen any evidence to totally convince me that it is always necessary. If you can find a manual car, definitely the cheapest and easiest way to do it.

[Peter7307]

Hi folks, just a few question about 4 speed manual gearboxes for a W123:
- Is the 4 speed gearbox the same on petrol and diesel cars?
- Can you get brand new bits (bearings, synchros etc - maybe from our forum sponsor?) or is it a case of finding another gearbox and doing a 'wrecker rebuild'
- How much time / effort is required to say, replace a synchro and has anyone had to do repairs or something similar before?

I know most of us have slushboxes but I'm sure it's been done before! Thanks guys! :lol:

Pastelgrey300D,

Rebuilding a manual gearbox is something usually needing some specialist tools and definitely a transmission manual for that particular gearbox and , for a once off effort , I would suggest you either find a transmission specialist or a place offering an exchange gearbox.

Perhaps one of the sponsors may be able to suggest a place?

A "wrecker rebuild" is a last resort. The box you get may be as worn as the one you have and most likely in the same places.
Then you still have the costs for the new bits like synchro cones , selector saddles etc which are the bits that wear.
The gears themselves usually last the life of the car or more provided it isn't driven by a complete dolt. Even if it is the car makers usually provide some insurance by having some sacrificial parts somewhere in the driveline.
The bearings are again normally rebuildable but for a "one time" event it is unlikely to be worth the effort.

Replacing synchromesh cones and gearbox rebuilds is something I have done so often I have lost count. Mostly on Jaguars and other British cars with Laycock O/D units and without.

Is it rocket science? No , BUT you need to know what you are doing so it all works the right way when you fit it back in the car and lasts as long as the original does.

As a final note...having to rebuild a box which has been "rebuilt" already really irks any decent transmission place.
I have had some come in with first where fourth should have been , no reverse , completely locked , no gears at all available etc. etc. Having to explain this is going to take time and money to fix someone else's "repairs" (mainly because you have no idea what has been done and to what extent) doesn't go down well so if you are going to go the "take it to a transmission place" ; take it there in original condition.

Good luck , Pete.

[pastelgrey300D]

Thanks for the input guys, I just want to make it clear that I certainly wouldn't be doing this myself! I guess what I am really trying to ask is that if I needed to replace a synchro would it be a fairly easy repair for a gearbox specialist or competent mechanic - and can you still get new synchros if you just need to replace one or two?

Many many years back my Dad rebuilt the gearbox in his mini with the help of a neighbor who "had done it before many times" and reckoned it was a "piece of cake" - everything went back in allright, but the first time he selected reverse, the car made a very loud whine - apparently the reverse gear we put in had a slightly different PCD to the original and was not perfectly matched - the gearbox worked fine but was just very very noisy in reverse :lol: ! So much so that we would always try and find car park spots we could drive out of frontways because everyone would to see what sounded like an air raid siren look when we reversed! :lol:

I'm flattered at your confidence in my mechanical ability Pete, but gearbox repairs are way past my "take it to a mechanic" threshold! :lol:

[Hendrik]

Far as I know the Merc manny trannys are a straightforward unit with no mystery.
However finding a good repairer is a pain.

[LlewellynRozanski]

Is it slowly starting to not go into 1st gear at all? Because mine blew a little cog or clip for the cog that moved between gears to change them, as it was explained to me. Im not sure what it cost though, I think it was cheap because I got ripped off.
Good luck

[benzfan]

I don't know how mechanically inclined you are, but I'd be tempted to grab this and have a crack at it myself, if I couldn't find a good repairer.

[LlewellynRozanski]

I'd be thinking the same. If there's a Mercedes manual that describes the 123 gear box as a cross reference to that book and some special tools, I don't see why not either.

[pastelgrey300D]

Thanks for the input guys, unfortunately the project will never go ahead - I was looking at a W123 240D that Davide in Mclaren Vale had for sale - it had a worn 2nd gear synchro that would crunch on fast changes. But I was outbid (the joys of ebay :shock: ) so there's someone out there that obviously wanted it more than me! :lol: Having said that, I was informed that it came with a spare gearbox, so a swap would have probably been the cheaper option anyway!

Anyone else out there selling manual 240D's for under $1000? anyone? ..... anyone?

Ha! Back to the waiting game... but on the bright side I'll at least have more time to work on the Finnie! :D

[pjm1]

My 4sp manual (behind a 240D) clunks when going into reverse unless I disengage clutch and wait a few seconds. The lubricant level is OK. Is this cause for concern? I know virtually nothing about gearboxes as I've never had one fail in any car I've owned...

[MB300D81]

I have a manual gear box that came out of a 300D.
Not sure it would suit 240D. Does anyone know the answer?


cheers

[Tony From West Oz]

My 4sp manual (behind a 240D) clunks when going into reverse unless I disengage clutch and wait a few seconds. The lubricant level is OK. Is this cause for concern? I know virtually nothing about gearboxes as I've never had one fail in any car I've owned...

This sounds like there is a failure of one of the drive shaft flex discs, allowing some rotation of the shaft when the drive direction is reversed.
Select First gear and drive forward, then release accelerator and see if you get a similar clunk. If so, the flex disc is the prime suspect.
It could be a CV joint in the rear half shafts or something in the diff, but diff issues are rare.
CV joints tend to go clunk clunk . . . . , especially in reverse or cornering.

I hope this helps,
Tony

[pjm1]

Thanks for your wisdom again Tony, I'm guessing the flex discs are fairly straight forward to change?

[LlewellynRozanski]

In the manual it covers working the old girl into reverse as well. You are just supposed to de-clutch for a couple seconds before putting it into reverse though, might have even been talk of a double clutch. Sounds like a piece of good quality metal up against a fan right?

[griffis]

I have a 1980, W123, 240D, 4 speed manual - engine & gear box for sale as a unit. Whole thing was working before car was rear ended & shunted into 4x4 in front, taking out radiator. Bought back from insurer as the car was full of near new parts including new clutch. G box had just had rear oil seal replaced.

Located near Camden SW Sydney.

Make me a fair offer.

Regards

Sean