QVHK

The following is copied from an earlier thread on LSD https://mbworld.org/forums/e-class-w...ml#post4123662 and is now moved here for more focussed discussion.

"Hello All, I got a 1990 300CE 12V and I recently replaced my auto gearbox with a 5-speed manual gearbox (with the related flywheel, new clutch, new clutch master and slave cylinder, differential, etc.). Every thing went fine but the post-conversion performance is discouraging. The car feels somewhat 'soft' - acceleration in 1st and 2nd gear is pretty weak and the car cruise more quietly than before but the car can hardly pull from 4th and 5th gear. The manual gearbox and differential were taken from a 1992 300CE 24V so is it possible that the differential is a mismatch? My mechanic told me that my original differential's ratio is 2.65, but there is no similar inscription on the differential newly fitted to my car. Any advice on what might be the problem and what solution is available? Am pretty disappointed with the outcome of the conversion. The car used to run very well with a very willing and reliable engine (M103)." (Posted by QVHK on 18 June 2010)

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"The gear ratio will be stamped into the differential housing, as shown in this photo (the first numbers are the serial number, the last few numbers are the ratio). You will probably need to clean it up with a wire brush to read this this as it's often covered with grime or rust.

That said... the 1990 300CE (124.051) came from the factory with a 3.27 gear ratio and a 4-speed auto in the USA. In Europe it was also offered with 4-speed manual with 3.27 ratio, or a 5-speed auto and 3.69 gear ratio.

The 1992 300CE (124.051) with 4-speed auto had a 3.06 ratio in the USA. In Europe, it was offered with a 4-speed auto or 5-speed manual with 3.06 ratio, or a 5-speed auto with 3.69 ratio. (The 124.052's went to 2.65 gears in the USA.)

Sounds like you previously had a 3.27 ratio, and ended up with a 2.65 ratio, which would cause the problem. Since this is not at all related to LSD, you should probably start a new thread on this topic, and post a link here so we can follow the progress. Oh, and it would also help if you posted your location (USA, Europe, etc)...
(Posted by AMGDave on 18 June 2010)

QVHK

Thanks, Dave.

Forgot to mention my 300CE is in Hong Kong (hence RHD). Chassis: 124.050, Engine M103, originally fitted with 4-speed auto gearbox.

The vehicle where the 5-speed manual gearbox came from is a 1992 300CE 24v (source unknown, somewhere in Europe), but the seller claimed that the manual gearbox on his CE is for M103 (717.433). As power seems to have gone down after conversion, I am researching into the final drive ratios to see if things could improve if I find another axle that would fit - the question is, which one? There are many specs out there. Mine has ABS not ASD/LSD. Any advice would be appreciated. I am trying to trace the seller to find out more about the manual gearbox and axle that came with it, but I wonder whether they were original on his 24V. I understand from literature that only the first batch of W124 of 1988-89 has manual transmission?

AMGDave

Hmmm... well, the first thing I would do is crawl under the rear of the car, and take a wire brush to the area on the lower/passenger side corner of the diff housing. That should clean it up enough so you can read the numbers. That will tell you what diff is currently installed.

Since you have a 124.050 with M103 engine (not a 24v), that would have come with a 3.07 gear ratio (in the smaller 185mm size). I still suspect you ended up with a 2.65 ratio from the Euro donor car, but reading the number off the diff will verify this.

Here is another photo showing where to look for the numbers. This is a 210mm diff installed on a 500E, but the location will be the same on your CE, with either 185mm or 210mm diff:

Chappy

I'll wager the gear spacing isn't suitable for the M103. The extra 40hp and higher torque of the M104 were a better match.

QVHK

Differential's specs checked. 3.07 Original on my 4-speed auto transmission 2.87 Now used on my car after conversion with the 5-speed manual gearbox The reading difference seems minor but acceleration at low gear seems to have weakened than before. Which version 3.07 or higher should I acquire to improve the situation? The topography of Hong Kong means we have many hills to climb sometimes.

AMGDave

Wow... the change from 3.07 to 2.87 should have been minimal. I suspect the individual gear ratios on the manual transmission may not be appropriate for the M103, as Chappy mentioned above.

Can you find out what manual transmission you have? The type & serial number should be stamped on the housing somewhere... should be somethinf like "717.450". Then you may be able to find the gear ratios, and compare to the original auto tranny. I'm thinking that a 3.27 may help but depending on the exact 5-speed trans you have, something even lower might work. It mostly depends on the 5th gear ratio, if it's 1:1 or if it has overdrive (something like 0.80:1).

:o

QVHK

Thanks, Dave. I was told that the gearbox and final drive came from the following vehicle: VIN WDB1240311B69335, the gearbox reference is 717.433 Too bad I don't know the gearbox ratios.

AMGDave

Can you double check that? The 124.031 chassis in Europe/Japan is showing a rear axle of 3.27 with a 5-speed manual trans 717.450 which doesn't match your info above. The 717.450 tranny was used on the 124.031, .032, .051, .052 and a few others. It has a 1:1 fifth gear (no overdrive) and would normally be used with a rear axle ratio of approximately 3.07-3.27 or so.

Maybe the VIN or chassis wrong, if you are sure you have a 2.87 with a 717.433 gearbox. I did find that the 717.433 gearbox was used with the 124.030 and 124.050 (plus a few others), but not the .051 chassis. The 717.433 gearbox has an overdrive 5th gear (0.799 ratio) so it should be used with a pretty tall rear axle, i.e. 3.27-3.69 if you want the acceleration to be snappy.

Something isn't adding up here.... btw, the tranny 5th gear ratios are in the MB TDM (Technical Data Manual), Group 26, "Coordination transmission", in the footnotes. Sadly, it doesn't list the ratios for gears 1-4. I'm suspecting you may have the "overdrive" tranny with a way too tall rear axle ratio, which is causing the problem.

whipplem104

It just occurred to me to ask about your flywheel. What did it come from. And is it installed in the proper position. I would check your timing. Maybe even on a load dyno. I know there are different flywheels some have magnets on one of the trigger weights and some do not. This can effect high rpms.

whipplem104

Also on what Dave is getting at check your highway rpms in 5th at 60mph. This is a good reference for your final ratios. For example without overdrive and 3.27 you would be at 3000 rpm. With 3.06 around 2500 or a little above. With 2.87 around 2200rpm. You could also rev up to redline in each gear and get an idea about your ratios. There are dots on your speedo from the original shift points and you could compare if it needs to shift earlier or later in each gear.

QVHK

The flywheel also came from the donor car. The workshop said that the flywheel is heavier/thicker than the auto version, and there was some minor problem during installation. My workshop is a Mercedes gearbox specialist, but it had very little experience handling manual transmission. The Hong Kong dealer did not import manual versions - the more common stick shift versions we still see occasionally were the 190E 2.3/2.5 16v.

The flywheel could not spin freely on first installation, as space was too tight and the workshop had to saw away the obstacle to make sufficient space. The engine still refused to start after clearing the way for the flywheel - it started alright after the workshop replaced the flywheel sensor.

At the 5th gear, the CE maintains the speed of 85 km/h (we use Km rather miles in Hong Kong) at 1,800 rpm. The engine finds it a bit hard to reach redline now and even revving to 5th take a while. Would check on timing as you suggested.

QVHK

The car is now with a paint shop for body work so the mechanical issues have to be dealt with at a later date. Anyway, the mechanical issues identified for further investigation are: (a) gearbox ratio (b) differential ratio (c) timing. I also understand from some previous posts that lack of power at low end might be improved by replacing the OVP and EHA. The slight difference between a 3.07 and 2.87 differential does not seem to be the entire cause of the sudden drop in performance. Another suspect is the flywheel sensor. Does auto and manual flywheel share the same sensor? I don't have the part numbers to verify. I shall also try to tackle the speedometer issue. I bought an AMG White Dial Cluster (in km topping at 300 Km) but it does not work properly on my CE - the rpm went crazy. I suspect the cluster is again for the 24V version but wonder if replacing the speed sensor on the cluster would revolve the problem. The original cluster is also in Km but topping out at 240 km. The 24V version tops out at 260 km. The odometer of my original cluster is not working but the rest of the cluster works fine, so instead of fixing it I thought I might replace it with an AMG cluster altogether.

AMGDave

True, the slight change in rear axle ratios should not cause that much difference... however, the transmission gear ratios could very likely cause what you are experiencing. If you really do have a 717.433 tranny, it was not designed to be used with either a 3.07 or 2.87 ratio behind an M103 engine.


Assuming the 717.433 is similar to the 717.430, the ratios are:

1st- 3.856
2nd- 2.183
3rd- 1.376
4th- 1.000
5th- 0.799


By comparison, the 717.451 (no overdrive) has ratios of:

1st- 4.151
2nd- 2.523
3rd- 1.687
4th- 1.239
5th- 1.000

QVHK

Thanks, Dave. I shall be away for a few days so I will double check the tranny on my return. Anyhow, it obviously has overdrive because it cruises quietly but does not accelerate much in 5th. I presume that a differential with 3.27 ratio is easier to find than a 717.451 manual gearbox; it is also a less difficult job for the workshop?

AMGDave

Most definitely. It would be far easier to swap the differential and get a different gear ratio. Since you have the overdrive tranny, a 3.27 axle would be a 2.62 final drive in 5th gear. I would get at least a 3.27 ratio, and I'd consider 3.46 (~2.77 final drive in 5th) or even a 3.69 (~2.95 final drive in 5th).

QVHK

Thanks, Dave. Where else can I find these higher differentials? I suspect that local breakers in Hong Kong may not have them, and shipping one from overseas would be expensive.

AMGDave

That's a good question. The axle ratios were different in Europe vs USA, so I really don't know what years/models you would look for locally. The diff weighs about 100 pounds when boxed up so yes, it would cost a small fortune to ship overseas. I'm also assuming you want a 210mm differential, although with a M103 engine the 185mm would work fine (unless you plan on forced induction, or an engine swap in the future).

The early R129 SL320 (92-94) had a 3.69 ratio in the USA, and the 1990 coupe had a 3.27 ratio, both in 210mm size. You may have to dig through the EPC and see what might work, then try to locate one locally. I'm sure you could find one pretty easily in the USA, and relatively cheap too ($200-$300 USD) but shipping could possibly cost double that or more.

QVHK

Thanks, Dave. I was away and just returned. We do have lots of R129 either 3.0 or 3.2 models in Hong Kong. Hopefully I can find one locally. How are 185mm and 210mm differentials different, and can I install a 210mm onto my car? Also, my CE has ABS not ASD or LSD, and from earlier posts I understand that differentials are also ABS and ASD/LSD specific?

AMGDave

The 210mm is stronger and is designed to handle more torque. It should physically bolt up, however the input flange may be a different size than your existing diff, requiring either swapping the flange, or the rear half of the driveshaft, to match.



ABS diffs and ASD diffs are very similar, in that they both use a single speed sensor at the pinion. You can convert an ASD diff to plain LSD and install it in an ABS car if desired. What you want to avoid are ASR diffs, which have no sensor at the pinion, and have two sensors at the output flanges. ASR diff housings cannot be used on an ABS car. Just make sure the donor diff has one sensor in the side, not two sensors on the top, and it should be ok.

QVHK

Thanks again, Dave. Noted that W126 300SE has a 185mm differentials with a ratio of 3.46. I am looking around for one locally. Also, from other posts, I understand that as the speed has a wrie/chain connected to the differential, I have to change the speedo to match as well or else the reading will be incorrect?

AMGDave

The W126 diffs use a different housing that will not fit in a W124. The donor has to be a W124 or early R129, or possibly certain W140's or W201's.



Ah, yes, good point. The speedometer is mechanical and driven by the transmission, but yes the speedometer must match the gear ratio. It should be fairly easy to find a W124 speedo for up to a 3.27 ratio, but I'm not sure how easy it would be to locate one for 3.46/3.69 ratios. Worst case, you could have a speedometer correction box created which goes in-line with the existing speedo drive cable, custom for your gearset.

QVHK

Thanks again, Dave. I checked the W126 differential number and confirm its ratio to be 3.46. I thought 300SE and 300CE share the same engine and differential. My brother totalled his W126 two months ago so I thought I could take the differential and speedo cluster to make a perfect match. Too bad if W126 and W124 do not share the same differential. The search continues....

QVHK

Fellas, here is an update. Found a diff. with ratio of 3.67 from a local W124 enthusiast and installed it on my 300CE. Some modifications (swapping certain components) made. Car now back to life! However, the next challenge is to calibrate the speedo. The reading is about 10Km to 15Km faster than the actual speed. Any advice how to make the adjustment please? Earlier on, I bought an AMG Cluster (max 300Km/hr) but it does not fit either.

AMGDave

Excellent! Glad to hear that worked. You need to get an instrument cluster from a W124 with 3.67 gears. Maybe check and see if the same guy you bought the diff from, also has the matching speedometer? The other option is to have a speedometer shop make a custom converter box that goes between the speedometer cable and tranny, but I'd try to get the proper speedo if possible.

QVHK

Thanks, Dave. He doesn't have the cluster instrument that matches the 3.67 differential. Would need a converter for sure. Also, the trip meter of my cluster is not working. Do the speedo and trip meter work on different mechanism?

P.S. I shall be away for a week and so may not be able to respond in the next few days.