W115 W123 steering gear differences - PeachParts Mercedes-Benz Forum

I6dzl · #1 01-12-2018, 10:55 AM

I would like to convert my 240D to manual steering. As everyone knows, W123 manual boxes are like a needle in a haystack. Seems W115 are a lot more common.

I am capable of fabricating parts, but do not want to do anything crazy.

What I really need to know:
Will a 115 box bolt up to a 123 frame?
Will I be able to use the 123 pitman on the 115 box?

I suspect I can custom fab something to make the steering shaft work if needed.

Thanks in advance!

t walgamuth · #2 01-12-2018, 12:04 PM

They may be a direct bolt in. The 116 is I believe.

greazzer · #3 01-12-2018, 01:24 PM

I don't know ... I would be cautious when it comes to this if you have to mod the steering because if you had a problem while buzzing down the interstate, that could turn out bad. I know the pittman arms are particular to the boxes. There were a few flavors of these over the few years MB had manual boxes in W123sl

t walgamuth · #4 01-12-2018, 09:44 PM

One of the steering boxes at least that i took from a 123 had a 116 part number. I don't know about the arms but the boxes are interchangible.

greazzer · #5 01-12-2018, 10:00 PM

The info should be in chapter 46 of the FSM. (I think its chapter 46).

I6dzl · #6 01-12-2018, 10:24 PM

FSM will give part numbers or actually detail differences between 115 and 123 boxes?

t walgamuth · #7 01-12-2018, 11:27 PM

check part numbers here for steering boxes on the two models in question.

greazzer · #8 01-13-2018, 07:31 AM

What I am trying to get at is that you apparently cannot mix and match pittman arms. There might be a ton of steering boxes out there. That is totally irrelevent. Finding a manual steering box is perhaps one of the rarist items out there. If you find a manual steering box, make sure it has its original pittman arm on it. Then, make sure you get the 369mm lower shaft and if the firewall grommit is intack, then that is a nice day at the yards. If you find one from a W115, then I don't know if it will bolt into a W123. If you found one at the yards from a W115, make sure you grab everything. However, you are still in the same exact boat in that it might not work. If that is the case, I would not try to fab or mod it. Just find a W123. I say this because there's one thing about mods. If they go horribly wrong, you need to know to a 100% degree of certainity if it can be "stopped" or at least that is my thinking. Buzzing down the interstate with the steering going wild is not something which can be stopped. I would not even try welding the lower steering shaft with a 2" extension. Whereas if your EWP goes bad while driving, worst case is the car overheats a little and you shut it off.

I6dzl · #9 01-13-2018, 12:25 PM

Got it, thanks for the info. I can get a box for $65 from a 115, not sure if that’s cheap enough to want to experiment with.

Were there actually any 123 cars with manual steering in the US?

BillGrissom · #10 01-13-2018, 01:13 PM

Re power steering gear boxes, I was just at PickNPull and their Hollander printout shows 1990-85 280CE/E & 300D/TD gear-boxes interchange. Might also be true for manual gear-boxes. Not sure why they don't list 240D. I know 82-85 300SD gear-boxes are different. Of course, doesn't say the Pitman arms interchange. If my 1960's Mopars are a guide, when changing from power to manual gearboxes, one needs a longer steering column rod to reach, so check that. There are after-market adapters (expensive) for Mopars, but wouldn't work for a W123 rod.

I find a gear-box in almost every 300D/TD I see at PickNPull (2 yesterday), but all are as worn as mine, showing 5+ threads on the sector-adjustment screw. That makes ~6 I have looked at in the last few years. I once found one w/ only 1.5 threads showing and thought "great", but thought to adjust it before undertaking the big removal task. After adjusting out play, it had ~6 threads showing, meaning they probably drove it like old movies, toggling steering +/-20 deg on a straight road. Getting tired of pulling together all the tools to hopefully have the enough to pick a gear-box then haul them home unused. P-P sells a rebuilt gear-box for $516.50. Rock doesn't list one. Hopefully, they replace enough hard parts to get the adjustment back. If not, it may have limited life since some part inside these boxes appears to wear in every car.

greazzer · #11 01-13-2018, 02:05 PM

The manual steering was up until 80' or 81' IIRC in the W123s, so that narrows the year range (1977-1980/1), so only 4 or 5 years.

I know the one set-up I got came from a car from the Lone Star State. Another from Germany with the lower, longer steering shaft from Denmark.

If $65-ish may break the budget or at least the interest in this, keep in mind that unless you get lucky and do a JY score, getting what you need will probably cost you in the ballpark of $500 or more.

leathermang · #12 01-13-2018, 03:35 PM

Is this because your power steering pump does not work..
or you are trying to get rid of it ?

the steering ratio may be different for the 240...since it was a lighter front end...

I6dzl · #13 01-13-2018, 03:48 PM

I am going for a bare bones fuel sipper project, similar to what Greazzer is doing. I would like to remove the power steering altogether.

$65 doesn’t break the bank, but potential for it to be a waste has me thinking twice. I’ll try to research pitman arms a little more.

t walgamuth · #14 01-13-2018, 03:53 PM

I thought about converting too when I was autocrossing my 84 280e. to reduce weight... Larry had one on an old 240 he no longer drove. That is the one Greazzer bought I believe. I tried to buy it from Larry IIRC but he did not want to remove it. I did not think it was worth driving to Texas to get it.

As for fuel economy it can't surely take much to turn the pump when you are not moving the wheel.