Thanks, that's good info. The article also says, "The usable power band lies between 3,000 and 5,000 revs per minute." I guess that's just about the state of the art for diesel engines.

I have to find out the grade of the rather significant hill that I climb every return trip from CT. The SD can hold 67 mph on that hill. I'd bet that it's 5%.

I would think you could hold 64 mph on a 6% grade with a 2.88.

Seems like a small sacrifice.........??

That sounds about right, now it usually stays in the 75 mph range on a 6%. I'm not sure how strong my engine is with 400K miles, so I don't know how it would do with 2.88 gears. It's more likely that I will change the gears when I eventually do the engine.

If you can hold 75 mph on a 6% grade........you've got a hell of a good engine.

I don't think the SDL's can do any better with 25hp additional. But, they are saddled with 2.88's so that gives back 13% of the hp right there.

I absolutely love the 2.88 in the SD. I cruise at 68 mph and you don't even hear the engine. It's like you fellows driving at 60 mph when the larger tires are considered.

It would be nice to have more quiet at highway speed, it's definitely worth thinking about. Then I would also have to find myself a speedo from an '85 300D. Hum....

Yep.........the W123 is cable driven.........so, I can't suggest my really cool solution on the SD: an electronic speedometer recalibrator. Takes the signal and gives you any output you wish. So, my odometer is accurate within .1% even with the much larger tires. If I change to 15" wheels (next tire change), I still can get accuracy within the same .1%.

It's fantastic. Definitely worth the $80. Sorry........you cannot use it.

I'm already running 205 tires, so that's getting me a couple of extra percent, about 26-2700 rpm at 60 mph.

Yup, those are cool, you can play with tire sizes and gears all you want without replacing the speedo.

I run 2850 at 68 mph.

215's

Cool, maybe if I find big enough tires I won't have to mess with the gears. Let's see, if I could fit 235s in place of my 205s I would have the equivalent of 2.88 gears.

What aspect ratio 215s fit on your W126, 215/70?

Yep, she's got 215-70-14's but I'd never recommend them.

Next set are 215-65-15's. Perfect for the W126 with the 15 hole wheels.

You should consider 205-65-15's on the W123.

I would if I could find some 15-inch bundts (they would be about 1% larger diameter than my 205/70-14s), I don't really like the looks of the later wheels on a W123.

Well, it's a personal choice. I've seen the 15 hole wheels on the W-123 and they do look attractive, IMHO.........but, definitely not period correct.

Good luck finding those 15" Bundts at a decent price.

As far as I can tell; it's good luck finding them at any price.

I keep hoping I'll get lucky someday and stumble across a set.

Yep........one never knows..........I'll keep an eye out for you...........I've got a few connections..........