I have a 1987 300 sdl and I'm looking to put a tall rear end gear in to lower the rpm's. I run it on the highway 75% of the time and I'm turning about 3000 rpm's at 70 mph. I do get about 30 mpg though but I believe that would improve with a different gear. Any idea's would be helpful.

Mike

I'd be really interested in what you find if you make that mod. I've been mulling the same possibility to save fuel and I believe the engine should be fine turning about 2600 rpm at 70 mph.

One of the V8 gassers of that vintage should have the 2.47 for that swap.

That has the 287 rear end right?

The 300d of that era with the five also carries a 2.65 rear IIRC which would be some improvment.

I am with Brian though I'd probably go for the 247 or even a 224 from a euro if I could find one with the price of fuel these days!

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I'm not aware that a diff from a W124 would fit a W-126??

Rear mounts are different but maybe it's just a matter of chaning the rear cover.

I don't remember the top mounts of a 126 diff.

Sixto
87 300D

I think the later v8s have a bigger diff but I suspect (don't know) that the 124s would be very very similar.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

V-8s have a 1.3L case, vice the inlines with a 1L case. I'd bet that if you had all the stuff, they would interchange.

W126 is similar to W123, is similar to R107, W124 is similar to W201, and never the 'twain shall meet. Different mounting style.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

The gears interchange inside the cases between the 124/190 and the 123/126 early, I believe.

So I guess it adds a level of complexity.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I've been meaning to do this for the longest time. Just the cost of No 2 has me rarely driving my Diesel vehicles at this point.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

A W126 is a W126 those are the parts that will fit. If you want your ABS to work you need the rear end from a 1986+ W126.

Just find a 560SEL in a junk yard and steal the rear end, I think its a 2.47. Plus its a limited slip which is nice to have.

Report back on how it runs up hills.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Well only 86+ fit the 86+ as the subframe out back changed.

I'm on the lookout for a 2.47:1 for my 300SD with ABS, so it'll be from an '85 500SEL

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]