Are my revs too high?

[UK280SL]

I have a 1969 280SL which I've had for 3 years and been totally happy with it - when I bought it the engine and gearbox were rebuilt by a marque specialist.

I'm currently trying to sell it and a potential buyer has had a classic car mechanic check it out (not a merc expert).  Overall he thought it was great but he did think it revved too high.  As far as I remember it hasn't changed since I bought it and I've always had it well serviced but he's now planted a worry in my mind.

At 3000 rpm, the speedo is showing about 55mph - he thinks it should be higher, but I have no idea.  the gear shifts are perfectly smooth and the garage who services it for me says it's fine.

Can anyone put my mind at rest?

Many thanks

W

[jameshoward]

Well obviously the engine, gearbox and diff operate in a fixed ratio. I assume the non-Merc expert isn't a non- mechanical expert because it rather sounds like a bone statement on his part.

Putting your mind at ease will be quite simple, however. Get under your car and get the 3 figures stamped on the rear diff, ie the large metal spherical housing in between the axle tubes. Look for a machined surface about an inch long and half inch high. You're looking for the diff ratio, and it will look something like 3,46 or 4,08. Something like that. Scroll down here for a pic of where to find it. http://www.sl113.org/forums/index.php?topic=18796.0

Armed with that, you can check the figs against this excellent graph: http://www.sl113.org/forums/index.php?topic=18239.msg127406#msg127406

Judging from what you say, I think you have a 4,08 rear end, which would give you 55mph at 3000 rpm. Simples!

Your buyers mechanic sounds like a muppet. Better warn the potential buyer not to let him loose on the car!!

Come back and let us know what you find.

[UK280SL]

James, thank you so much - you have reassured me - and I'm only sorry I couldn't find the link without you having to post it again.  I will look underneath but your chart looks spot on right through the rev range!

The mechanic had a number of classic cars for sale but no Mercedes.  I had my doubts about him when he said the gearbox had a problem because there were only 3 gears showing when he drove it.  I had to point out that it starts in 2nd when in "4"!

The trouble is that the buyer who hired him obviously listened to him rather than me and now I've lost that buyer.  At least I now have a rationale for the next potential buyer if it get's raised again.

Once again, many thanks

Warren

[jameshoward]

Warren,

You're welcome. Point the potential buyer this way to the site. He will be reassured and can ask all the questions he likes.

Good luck.

James

[Neil Thompson]

Why not offer the car for sale on this forum Warren?

Neil

[UK280SL]

Hi.  It's on car and classic but yes I will put it here as well.  I have a viewer tomorrow morning but if that doesn't work, I'll be back.  Many thanks.

[Cees Klumper]

The very first thing that struck me when I test drove my first Pagoda was that it seemed to rev too high, and was missing a gear. Since buying that same car, I converted the US standard 4.08 to a more reasomable 3.69 differential.
So for anyone not familiar with this particular car to notice the same thing is not strange. Too bad it was a trusted advisor of a potential buyer though.

[jameshoward]

You have a point, Cees. Someone once described first gear on my car (was 4,08) as being suitable only for towing large caravans up Swiss mountain passes. He had a point, too.

The change to the 3,46 has made a huge difference, but I do miss the more spirited driving of 3rd gear and the old diff. However, I think on balance the whole package is better with the 3,46 for me, as I tend to do longer drives. My friend with a Mk 1.5 E Type, (straight 6, 4.2L (I think)) seriously leaves me standing now. That wasn't always the case.