teezer

from my 124 notes, speedo tags to rear gears

3.69 ~ k=1425

3.46 ~ k=1330

3.07 ~ k=1200

2.88 ~ k =1100

these are stuck on the rear speedo casing

the_widebody

there is something not right about you saying that the flywheel needed to be cut to fit, the 103 and 104 cranks have exactly the same ends, and flywheels from either should fit straight on with out any mods being required. i wonder if your kit is off a 201.

QVHK

Was unable to reply as I was away on holiday and just returned.

(1) There isn't much local expertise available here on speedo calibration.
(2) Yes the stick shift mechanism and related parts were removed from a 1992 300CE24. The workshop also thought that it should be a direct fit. Only when the car did not fire up did the workshop found that the flywheel was stuck due to tight fitment.

The car performs fine now, but calibrating the speedo is now a priority as local speed checks are conducted quite frequently.

What calibration kit did you try and where did you get it?

QVHK

I have three more questions:
(1) is mine a mechanical cluster instrument (WDB124050)? There is a sensor component at the back of the cluster.
(2) does the chain connects the diff to the instrument, or connect the gearbox to the instrument?
(3) the travel meter wasn't working even before the change, probably due to gear failure inside the cluster instrument. Does fixing the speedo also automatically fix the travel meter?

(1) will affect what corrective device to use (digital or mechanical)
(2) will determine what factors to take into account when coming up with the correction "k" value. In my case, I have replaced a 4-speed auto gearbox with a 5-speed manual gearbox, and a differential with a final ratio 3.07 with one with 3.67.
(3) I found some sites that offer replacement gears inside the cluster instrument, but was told that I must remove the old ones and count the "teeth" before ordering.

AMGDave

1) Mechanical. All W124's have mechanical speedos except the V8 models
2) Transmission to speedometer - the speedo must match the gearing to be accurate, the transmission used is irrelevant
3) Yes, it should; if you have the speedo repaired they should also repair the trip meter. I am not familiar with replacing gears inside the speedometer, you would have to consult a VDO repair shop for more info

QVHK

Thanks for the data. How may I make use of such data in calibrating my existing speedo, bearing in mind that my existing cluster was originally paired with a 3.07 diff, and now I have replaced a 4-speed auto gearbox with a 5-speed manual and a 3.67 diff? Would some device such as the "yellow box" help, or are there similar device which could do the trick?

AMGDave

The YellowBox (or similar) will only allow adjustment of electronic speedometes, not mechanical - can't use that here. Basically you would want to locate a mechanical speedometer from a car with a 3.67/3.69 rear axle ratio (no matter what tranny it had). Or, perhaps try to find a VDO repair shop that can modify you speedometer to work with the 3.67 ratio, by installing different parts inside the speedometer itself?

QVHK

Thanks, Dave. There is only one local VDO shop which does repair and simple modifications (like backlight colour, etc.). Expertise is limited and reputation is so so (mainly reliability issues), so I am looking overseas. There is also no hope to find a local match. There is definitely no 3.67 version locally. Moreover, the local market is very small, and most Mercedes are exported overseas once they hit the scrapyard; only those seriously wrecked are stripped for parts. According to my mechanic, the revolution cable links up the cluster with the gearbox, not the diff. His advice is again to find a cluster that matches the manual five speed gearbox. It boils down to what Mercedes model uses the 5-speed manual gearbox (717.433) as original equipment, and is the matching instrument cluster still available? I too have one AMG cluster that max out at 300 km/h and 8,000 rpm, but it does not rev properly after the gearbox and diff conversion, so I have to presume that modification is the only way. Some relevant data here: original instrument cluster max. speed 240 km/hr; RPM max 7,000 original transmission: 4-speed auto (on a 300CE 124.050 version, M103 engine) Gearbox now: 5-speed manual No. 126.260.2801.717.433 (01840-833) Differential final ratio: Was 3.07 Now 3.67. I have done an Internet search and found a mechanical device called “Halda SpeedPilot” http://www.winktimber.com/vintageral...dpilot_bj5.htm which calibrates and corrects the speedo as well as the odometer, but can’t find how to get it. I know car modifications are very common in the US, and trust that there may be other ways to tackle the speedo.

AMGDave

That is correct. It does connect to the gearbox.



He is wrong. The speedometer is not different for each gearbox! It varies with the differential gear ratio. That is why you need a speedometer for a 3.67 ratio, NO MATTER WHAT TRANSMISSION IS INSTALLED.



You'd have to find a W124 that uses the 3.67 ratio, and see if that speedometer is still available to buy new... it may be available, but expensive.




That looks interesting... if it will fit the VDO speedometer, it might work fine!

QVHK

Thanks, Dave. Today, I was driving in parallel with a public light bus ('crew bus' in the US) which has a major digital speed display (a speed monitoring device for passenger safety). It showed it was doing 44 km/h, whereas my speedo reading was 57 km/h! This is a huge discrepancy. Have to work harder to find a way to correct the speedo.... What W124 model that uses a 3.67 final gear ratio?

QVHK

I found another mechanical device that neatly attaches the correction adaptor to the cable lead at the tranny. Check this out. http://www.yotatech.com/f116/mechani...l-pics-195986/ However, that discussion was some years ago so am not sure if this device is still available and if so if it also suits Mercedes. Has anyone tried this product before? If available, it will save the trouble of finding a new instrument cluster, and the correction device will also fix the trip meter.

AMGDave

Cool! Looks like it's worth a try:

Commercial Speedometer
2446 Evergreen Avenue
West Sacramento, CA 95691-3091
(916) 371-5873

I think you'd have to do it at the speedometer end of the cable, not the transmission, but it may still work OK.

QVHK

I finally removed my instrument cluster and found similar reference on the speedo casing. The original differential ratio of my 300CE was 3.07, the value of K is 735, not 1200. Maybe because mine is a Hong Kong car that uses Km/h (not mph, US style speedo).
[post script: but my instrument cluster is already a replacement, so the original cluster may have a slightly different configuration. W124 E220 (not available in the US) has the same speedo layout i.e. 240 kpm maximum and 7000 rpm.]
I am going to order a speedo ratio adaptor to match my new differential ratio of 3.67. What it will do is to adjust the cable revolution downward by about 19.5%.

Incidentally, I found an AMG white-face 300 kph 7000 rpm instrument cluster claiemd to be taken off an E420. I actually bought another AMG instrument cluster last year thro' another enthusiast, it is 300 kph, 8000 rpm. I only realized belatedly that the sockets at the back of the instrument cluster and the differential have to match.

QVHK

Here is an update on the instrument cluster. Did a lot of web search and found two that matched the 3.67 differential. This was a lot of work as most offerings did not specify which car on which the cluster was used, and no K-vlaue specified in the ad or listing. Sent over 20 emails and reminders and only got a few responses - disappointing. I guess it is not the language but a phobia to do business outside of the European Community - too much trouble working out and arranging shipment etc. Anyhow, found one thro' Germany eBay. Arrived after nearly 3 weeks and everything looked great and functional. Alas, the techometer reading was 30% higher than the norm, and acceleration by downshifting shot the rev far beyond the red zone, causing the engine to cut out by itself a few times (the needle stopped and stayed beyond 7000 rpm). Also noticed that the speedo reading was about 10 km higher than normal. Told the seller and seller said impossible, claming that all was checked in order before shipping, but nonetheless agreed to take it back and arrange a full refund, including outward shipment. Found another from Sweden and only needed the left and central (speedo) meters to save shipment (shipment to Hong Kong costs much more than the item itself) - I can reuse my own techometer. Everything works fine, but same as the earlier from Germany, again the speedo reading is about 10 Km higher than actual. Examined the meter closely and it did not appeared to have been repaied or fiddled with before. Have confirmed with the specs that the instruement came off from a W124 with a 3.67 differential - same as the one on mine. The K-vlaue of my speedometer prior to the gearbox and differential was 735 (for 3.07 differential, metric scale). The K-vlaue of the replacement instrument cluster (for 3.67 differential) is 875. I have seen K=880 in other W124 models but using 3.69 differential. So, what might be the problem?

the_widebody

the fly wheel should fit straight onto the 103 or 104 engine.

i suspect that they either cut down the crank position sensor (but would expect that to stop the car working).

When you change from auto to manual, there is a spacer that you should fit between the block and the crank position sensor to space it correctly for the manual flywheel. maybe they did that first, which caused the no start? then fitted a new one with a spacer?

it is more likely you have been sold mis matching items, mabe a twin mass flywheel and a long input gear box! this may explain why your diff was also wrong, you were sold a bitsa (bits of this and bits of that).

QVHK

Thanks. I was told the space was tight when they replaced the flywheel and installed the gearbox. Rahter than using spacer they have to do a bit of cutting, and replaced the flywheel sensor to restart the car. Anyway, the car now works fine and I am most satisffed with its post-conversion performance - car still accelerating at 5th and pulls like it can go on forever. But now that the 3.67 differential and the instrument cluster are a match, I have no idea of what is wrong. From earlier posts, I understand that this has nothing to do with the gearbox, only the differential. I am using 215/45/70 front and 225/40/17 rear wheels, could size alone result in a higher speedo difference of 10 km/h?

teezer

rear tire diameter affects your speedo readout

i think there were 2 stock tire sizes

185/65 X 15 which are 24.3 diameter
195/65 X 15 which are 25.0 diameter

i find your 225/40 X 17 are 23.8 diameter

using this calculator <http://www.corral.net/tech/gearcalc.html>

and plugging in all 3 tire sizes ~~~ 185 = 59.5 mph, 195 = 60.74mph, and 225 = 58.57mph

this was using 3000 rpm and trans gear ratio of 1.00 and rear axle 3.67

QVHK

Sorry; corrections: my tire sizes are 215/45/17 front and 225/45/17 rear. If the diameter of the rear tire is larger than the stock tire, should not the speedo reading be under than over, while the actual speed would be higher?

AMGDave

225-45-17 is a correct size for a 124 chassis - there should be very little speedometer error, less than 2%.

When you mention speedo error it's best to mention the percentage error, not kph. If it's 10kph off at 20kph, that's huge (50%), but 10kph off at 250kph is pretty small (4%). The percentage should remain the same regardless of speed, i.e. if it's 5% off at low speeds it should still be approx 5% at high speeds. If it's a flat 10kph off througout the range, that usually indicates a mis-placed speedometer needle, but I seriously doubt you'd get two in a row doing the same thing...

QVHK

Thanks, Dave. The speedo reading of the two speedometers I sourced from Europe both shows an almost 13% error above actual speed. I can only suspect that the 3.67 differential on my car is actually a 3.27 one on a 3.67 casing, but is this possible? Car now runs at 85 kph in 5th at 2000 rpm. One way to find out is to use a speedometer from a W124 with a 3.27 differential?

AMGDave

One way to tell what the gear ratio is without removing the diff from the car & opening it up is to turn the input shaft & count the revolutions. You need to get both rear wheels off the ground and have the transmission in neutral. Mark a line with paint or chalk on both the driveshaft and one wheel/tire. Have a friend count the number of turns of the tire while you turn the driveshaft by hand and count driveshaft revolutions. Have your friend tell you when they have counted exactly 10 turns of the tire/wheel. You should have counted 36.7 turns (approx) of the driveshaft, if it is a 3.67 ratio. If you only count 32.7 turns, then it's a 3.27 ratio. A bit cumbersome, but effective...

QVHK

Thanks, Dave. Will try next time I visit my mechanic.

Shoomakan

I noticed you didn't find what your diff size was, so I thought I'd help. My car also does 85kph at 2000rpms, 100 at almost 2500. My rear diff ratio is 3.67 I believe, or 3.65. One of them, not sure what. I keep mixing up my BMW and Mercedes diff sizes, but it is for sure a 3.6x. See what came on our cars and you'll figure out exactly which size.

As for the slow performance, I had the same problem when I swapped my car. Check your ignition control module.

Another thing, my car's shift points didn't change, even with the manual swap. My speedo indicators are still accurate, surprisingly. And don't forget the cps flywheel sensor that you need to take into account. If your flywheel had fitment issues, I don't believe it's the correct one for your car.

QVHK

Thanks. I have not had time to verify the differential ratio with my mechanic, but your info revives my interest in the matter. I understand yours is M104 engine and if you have replaced your 3.27 diff with a 3.67 diff, and if you have not replaced your speedometer to match a 3.67 diff, it seems a bit weird if you still find speedo reading more or less accurate. I understand that the speedo reading is determined by the diff ratio, K value of the speedometer (i.e. how many turns the speedo cable revolves to make 1 km), and the actual size of your rear wheels. May I ask the K value of your speedo and what tire size do you use?

I still do not know why my speedometer is about 11% above actual speed. More common readings lately are:
Actual speed 80 kph (speedo reading about 89 kph)
100 kph in 5th gear at about 2600 rpm (but actual speed could be just 89 kph)
My engineer colleague believes that the error may not a constant but may vary with speed. We agree to find out if we have the opportunity of testing the car on the brake-efficiency checking platform (where tires roll against the drum rollers of the machine as if car is travelling – the machine will indicate actual speed, and we can check the speedo reading from the instrument cluster at different speed to record the discrepancies at different speed).

Some basic facts about my car and conversion:
Car: Year of Manufacture 1990, 300CE, W124.050; Right Hand Drive
Engine: M103 [103.983; unchanged]
Gearbox: 5-speed manual [version 717.433, probably taken from a W126; original gearbox was 4-speed auto]
Differential ratio: 3.67 (original was 3.07)
Speedometer (in kph) K value = 875 [matching 3.67 diff] (original K=725 for 3.07 diff)
Rear tire size: 225/40/17

Car is not slow but fast, especially at mid-range. 3rd gear pulls very well and max out around 160 kph (may be lower due to speedo error), but is sufficient to prepare car to overtake others at 4th. Haven’t try maximum speed at 4th or 5th, but at the 5th gear car is still very willing to pull even going uphill. While on highways, sometimes I wish I had a 6th gear to cruise at lower rpm, save fuel and lower the noise. Nevertheless, it is already much better than the 4-speed auto when the car almost stopped accelerating at 4th at 180 kph.

Shoomakan

I kept my stock diff ratio, which is why I'm sure my speedo is accurate.