W108 250 SE automatic gearbox - does it start off in 2nd??

[Tju]

Years ago, my Dad bought a Rover P5B, which coincidently, topped out at around 55mph, went throught the gears very fast and was absolutely screaming its Knutts off. I took it to a P5 specialist who removed the diff to find it was from a Land Rover, he replaced it with the correct diff for the car and hey presto, gearing was back to how it should be, your car (at some point in its 50 odd year old life) may have had a diff from say a W110 220D, (if compatible) which could possibly create the effect that your car is giving you, seeing that it seems you have all 4 forward gears, If it were me, I would remove the diff and check the ratios,

Hope this helps and good luck!

 

[Steve Longden]

Is there a rev counter on the car?
If there is one you can see the revs the engine is at when you are doing 55mph.

If there isn't one on your car as standard, I understand that it is possible and relatively straightforward to retro fit a rev counter.
You might not want to to mount it on the dashboard permanently but it might be worthwhile to fit it temporarily while you

Hi Yes I have been considering fitting a rev counter (probably temporarily) for exactly this purpose.

 

[Steve Longden]

That is the same gearbox as in mine. 4 forward gears and it starts in 2nd by default.

On a quick look your car should have a top speed of 118mph.

Is the speedometer reading correctly?
Maybe check it using another car driving at 50mph.

Speedo cant be far off, I haven't checked it exactly. It just feels wrong - way wrong. I mean its lovely to drive goes through the gears and all is well until it just runs out of speed in 4th. You just find yourself going much slower that you want on say, an A road simply because it's unpleasant cruising at the revs required to get to 60. On motorways it just feels like you're driving a regular car in 3rd
I'm going to check the diff ratio and get a rev counter

What does yours cruise at comfortably? (I realise that comfortably is objective)

 

[Steve Longden]

Years ago, my Dad bought a Rover P5B, which coincidently, topped out at around 55mph, went throught the gears very fast and was absolutely screaming its Knutts off. I took it to a P5 specialist who removed the diff to find it was from a Land Rover, he replaced it with the correct diff for the car and hey presto, gearing was back to how it should be, your car (at some point in its 50 odd year old life) may have had a diff from say a W110 220D, (if compatible) which could possibly create the effect that your car is giving you, seeing that it seems you have all 4 forward gears, If it were me, I would remove the diff and check the ratios,

Hope this helps and good luck!

Thanks

 

[Steve Longden]

Are we sure the transmission is changing up into 4 or is it staying in second or third gear, this would account for the high revs. Don't think a lower diff ratio would alter the revs that much.

I road tested it yesterday with the engineer that rebuilt it from Bristol Transmissions yesterday. He gave a good demonstration of 1st which almost immediately changed to 2nd when driven in L and 2,3&4 operating properly in D

 

[steveq]

Hi,

I think the final drive ratio of your car is:- standard axle ratio 3.92:1 or 3.69:1 (maybe that is market specific?).

I'm not sure how to check your ratio though.
I think you just need to put it in neutral, jack up one wheel, mark the propshaft and the wheel and then turn it to see how many revolutions the propshaft does for a full revolution of the wheel.
You would probably need to do a number of revolutions of the wheel to calculate the ratio properly as it is going to be very difficult to calculate 3.92 or 3.69 visually.

If your car is so dramatically slow, you could find the ratio is significantly different to the numbers above.

Of course, you should do it on flat ground and chock the other 3 wheels -- no point in calculating the ratio perfectly but getting squashed by a runaway car !!

 

[robparker]

These cars really aren't fast. I had a 250se a few years ago, I cannot remember the top cruising speed, but it was somewhere in the region of what you said, maybe 65, they rev really high but will do that all day

 

[RhodieBill]

Well here is, albeit a Coupe Version, but the same engine running up to 112mph (180kph) with relative ease. So 65mph should be a walk in the park....

As previously stated Steve, I would get it to a reputable Mercedes Specialist and get a 2nd opinion.

 

[alexanderfoti]

Yes, I agree with Steve, if you are 100% sure its shifting into 4th and the "kickdown" cable is correct adjusted so that its not staying in 3rd, then it could be a case of perception.

Does the car have a rev counter? If not, max its top speed (until you get to 70mph). It may be the case that the engine sounds faster than it is.

Whilst they are not fast, it should do more than 55mph.....

 

[Cornelis]

I road tested it yesterday with the engineer that rebuilt it from Bristol Transmissions yesterday. He gave a good demonstration of 1st which almost immediately changed to 2nd when driven in L and 2,3&4 operating properly in D

I road tested it yesterday with the engineer that rebuilt it from Bristol Transmissions yesterday. He gave a good demonstration of 1st which almost immediately changed to 2nd when driven in L and 2,3&4 operating properly in D

I have exactly the same problem with my 1969 280S. Km/h II-20 and III-40 where it should be II-50 and III-90 Ending with a top of the 55-60 mph that you mentioned. May I ask if you found a solution for this and if so what it was?
You mentioned 2, 3&4 operating property in D?