Looking for help in getting a 6 speed into my w123, sourcing from Italy/Germany - PeachParts Mercedes-Benz Forum

martureo · #1 01-08-2025, 12:11 PM

Here's the deal. I've got a s123 with a OM603a in it. I need to get a custom driveshaft for the automatic anyway, so I figured I'd hunt down a 5 speed manual while I was in Europe on business. There's plenty of them floating around for around 300 Euros or so. But now I've been introduced to a 6 speed manual option, and who wouldn't want that?

I'm looking at a 716.6XX

I'll be in Northern Italy from January 14th to the 28th and I'll have plenty of time to go wandering.

Here's the issues I'm faced with right now.

I'm having a hard time finding the shifter position/dimensions to see if this is a decent option
The checked luggage limit is 70 lb and the transmission is going to be at least 85 lb. Air cargo is at least $450 so I'd like to see if I can split the transmission into two luggage pieces. Any guidance would be helpful.
If anyone is local I'd love to find some support for getting it and inspecting it prior to purchase

I know this is a long shot, but if anyone has leads or info I would appreciate it.

greazzer · #2 01-08-2025, 12:48 PM

What do you need measured? I can measure whatever you need on a W123.

As for shipping- break up the components if you can and do the luggage deal. I’ve done it before and the lesson I learned is go to Italy’s version of Goodwill and buy junkie luggage to toss when you get home. Make sure to drain all fluids or it will be impounded, especially if it leaks.

In the U.S. I added a printed note to the TSA inspector advising what the part is

Steamboatsykes is in Italy now as an expat

Shern · #3 01-08-2025, 02:29 PM

This is interesting, please keep us posted.

I’m in Vienna if thats any help. Happy to check out anything locally.

Frank Reiner · #4 01-08-2025, 03:12 PM

Quote:

Originally Posted by martureo

I'm looking at a 716.6XX

The gear ratios of that box were intended for use with relatively small displacement gas engines, that have low torque at low RPM.
1st gear is very short - 4.46:1
2nd is rather tall - 2.61:1
6th is .84:1

You would use a 3.46:1 final, and in 6th would have an overall ratio of 2.9:1; not too bad, actually. However, starting in 1st would be an overall ratio of 15.43:1, which is very short for an OM603. If you started in 2nd the overall ratio would be 9.03:1, a bit tall for other than level ground.

A gearbox with an ~3.75:1 first, and an ~.81 top gear would work much better.

martureo · #5 01-08-2025, 03:57 PM

Quote:

Originally Posted by Frank Reiner

The gear ratios of that box were intended for use with relatively small displacement gas engines, that have low torque at low RPM.

That's one reason I was looking into getting one from Europe. They were found on the 2.2L CDI engines in the C203. I figured that would be a decent analog.

Quote:

1st gear is very short - 4.46:1
2nd is rather tall - 2.61:1
6th is .84:1

You would use a 3.46:1 final, and in 6th would have an overall ratio of 2.9:1; not too bad, actually. However, starting in 1st would be an overall ratio of 15.43:1, which is very short for an OM603. If you started in 2nd the overall ratio would be 9.03:1, a bit tall for other than level ground.

A gearbox with an ~3.75:1 first, and an ~.81 top gear would work much better.

I would love to know where you go the gearing for the 716.6, the numbers I got were:
1_5.014
2_2.831
3_1.789
4_1.256
5_1
6_.828

I know there's supposed to be a different gear spread between the 716.60/64 (spread of 6.1), 716.62 (5.5) and 716.66 (5.3). I'm thinking I have the numbers for the 716.60 and you have the gearing for the 716.66.

I was planning on using the w123 differential with either the 3.07 or the 2.88. With the 2.88 and your first gear (4.46) it would give me a overall of 12.8. Do you think that would be decent?

Frank Reiner · #6 01-08-2025, 05:01 PM

Quote:

Originally Posted by martureo

That's one reason I was looking into getting one from Europe. They were found on the 2.2L CDI engines in the C203. I figured that would be a decent analog.

I was planning on using the w123 differential with either the 3.07 or the 2.88. With the 2.88 and your first gear (4.46) it would give me a overall of 12.8. Do you think that would be decent?

The 12.8 1st overall would be fine; the 2.4 6th overall would not be.

The ratios I cited are for Chrysler products.

Those boxes are fine 5-speeds; either 1-5, or 2-6, depending on final drive.

BirthdayBenz · #7 01-10-2025, 06:42 AM

DPUK makes an adapter for the ZF six speed GS37DZ out of diesel BMWs which would probably have better gear ratios.
https://dieselpumpuk.com/products/adaptor-kit-for-bmw-zf5-zf6-gearbox-to-mercedes-om60x-engine?srsltid=AfmBOoo6G4ZW93IcTBbQCm0N1Nmcv7P8e88-IJZYayW5Nw2tBBT-_hpG

There also appears to be some of these 716.6 transmissions for sale stateside. I've never purchased anything from Benz Injection.
https://www.benzinjection.com/product-page/om60x-manual-6-speed-transmission-716-6

martureo · #8 01-10-2025, 07:54 AM

Quote:

Originally Posted by BirthdayBenz

DPUK makes an adapter for the ZF six speed GS37DZ out of diesel BMWs which would probably have better gear ratios.
https://dieselpumpuk.com/products/adaptor-kit-for-bmw-zf5-zf6-gearbox-to-mercedes-om60x-engine?srsltid=AfmBOoo6G4ZW93IcTBbQCm0N1Nmcv7P8e88-IJZYayW5Nw2tBBT-_hpG

There also appears to be some of these 716.6 transmissions for sale stateside. I've never purchased anything from Benz Injection.
https://www.benzinjection.com/product-page/om60x-manual-6-speed-transmission-716-6

Yeah, the 716.6 is available in the US, but the prices are a bit more attractive in the EU and they were geared for diesels in the EU. I've been checking out a few in the range of 200-500 Euros.

martureo · #9 01-31-2025, 01:31 PM

I was successfully able to get a transmission.

I found multiple 716.6 gearboxes in Northern Italy, but settled on a 716.631 that was in Gazzola, Italy. The seller was on ebay and on their own website. (GlobalParts https://globalparts-24.it/) I asked if I could pick up the gearbox as it was only a two hour drive from where I was staying. They said I could only get it shipped from the warehouse (which should have been a red flag) but shipping was free. So 185€ later, I got confirmation that it was shipped and I'd receive it in a few days.

For context, I was in Italy for two weeks and would fly out at 6 am on Wednesday, the 29th. I ordered the transmission on Tuesday, the 21st and was told it would be a few days.

On Thursday, the tracking number I was given updated the location of the transmission as Bielsko Biała, in Northern Poland. I was not happy and started to stress out. The transmission arrived at noon on Tuesday, the 28th, giving me just a few hours to figure out how to split it and get it ready for the flight.

Just in case anyone needs it, the tools needed are a 30mm twelve point, an E12 socket and E20 socket. First remove the screws on the rear of the case with the E12 socket. Then, using a flat head screwdriver and a hammer, remove the cover of the front screw next to the input shaft inside the bellhousing. You'll have to destroy this cover and pull it off with some pliers. Then remove the E20 screw. This will allow you to separate the bellhousing from the rear and the gears.

The transmission was 85 lb. The max for checked baggage was 72 lb. I had stopped by a second hand store and purchased two duffle bags for carrying the two halves of the transmission separately.

I checked in with Lufthansa and was surprised to learn that their baggage fees had changed. Previously I'd flown with them with the additional baggages fees (for bags under 50 lb) being 100€ each. Now the first bag was free, the second bag was 100€, but the third and additional bags were higher. If I checked the bags in online it would be 180€ for each additional bag, but if I checked them at the counter they would be 240€ each.

Faced with the possibility of the bags being almost another 500€ when air freight was 450€, I reached out to FedEx and tried to price a backup option. FedEx had a last minute rate of 280€ shipped to my house and 230€ shipped to my office. So I boxed the transmission up with some nice padding and shipped it through FedEx. 24"x 32"x20" and 98 lb.

So yes, it is possible to get a cheap 716.6 in Europe. It is a bit of fun to get it back.

BirthdayBenz · #10 02-03-2025, 06:19 AM

Quote:

Originally Posted by martureo

if I checked them at the counter they would be 240€ each.

Oh wow. Somehow I was charged 64 GBP to ship my GS637DZ transmission from the UK. This was with Ebay's global shipping program. I don't understand how it was so inexpensive.

CDTurbo001 · #11 02-16-2025, 05:28 PM

Quote:

Originally Posted by Frank Reiner

The gear ratios of that box were intended for use with relatively small displacement gas engines, that have low torque at low RPM.
1st gear is very short - 4.46:1
2nd is rather tall - 2.61:1
6th is .84:1

You would use a 3.46:1 final, and in 6th would have an overall ratio of 2.9:1; not too bad, actually. However, starting in 1st would be an overall ratio of 15.43:1, which is very short for an OM603. If you started in 2nd the overall ratio would be 9.03:1, a bit tall for other than level ground.

A gearbox with an ~3.75:1 first, and an ~.81 top gear would work much better.

I disagree - the 603 has a little flatter power curve than the 617A so revving a little lower at a given ground speed is realistic/comfortable. The 603, .84 overdrive, and stock 3.07 diff from a '82-84 turbo W123 will have very nice highway manners, without a drastic spike in RPM's when downshifting to 5th for more acceleration, climbing a hill when not going real fast in 6th, etc. It probably wouldn't be prohibitive with the late 2.88 ratio, either.

martureo · #12 02-16-2025, 06:22 PM

Quote:

Originally Posted by CDTurbo001

I disagree - the 603 has a little flatter power curve than the 617A so revving a little lower at a given ground speed is realistic/comfortable. The 603, .84 overdrive, and stock 3.07 diff from a '82-84 turbo W123 will have very nice highway manners, without a drastic spike in RPM's when downshifting to 5th for more acceleration, climbing a hill when not going real fast in 6th, etc. It probably wouldn't be prohibitive with the late 2.88 ratio, either.

This is good to hear. I was getting a little worried as the guys pumping loads of power from 603s and 606s have recommended this transmission, but I'm planning on a decent commuter.