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  #1  
Old 09-12-2019, 12:31 AM
Diesel user
 
Join Date: Jul 2018
Posts: 39
Thumbs up What to expect with a om617 and 2.47 final drive

Pictures are worth a thousand words, and video exponentially more. In the spirit of the recent thread regarding the 2.47 differential swaps, I have made a short video of my om617 with that differential in a W126:

https://www.youtube.com/watch?v=GEYDx9ilwoA


The video shows the shift points and sounds, however isn't exactly the most ideal quality... Turn down your volume to start and enjoy.

I have been running that ratio on this car since around 2003 and wouldn't go back. The car runs mountain roads at altitude, using all four gears you shouldn't have an issue at least with the turbo engine. This particular engine has a mostly stock injection pump(om603 ALDA), T3 turbo with 2.5" exhaust back to a stock v8 muffler, generic cone filter intake.

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  #2  
Old 09-12-2019, 12:53 AM
dude99's Avatar
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Location: Vancouver, BC
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My old 300SD has the 2.47 in it as it was a 380se conversion. I had no issue with it, acceleration was more than adequate and fuel economy was great. Never should have sold that car, sigh.
I found it years later but the owner didn’t want to sell it....
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  #3  
Old 09-12-2019, 04:28 PM
Shadetree
 
Join Date: Jan 2010
Location: Back in SC upstate
Posts: 1,838
Did you go as fast as you could?

What is the top end on level ground with that setup?
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  #4  
Old 09-12-2019, 05:02 PM
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Join Date: Oct 2004
Location: Grand Rapids, MI
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Top end is probably around 105-110....on level ground.....and it takes a while. It runs out of power before it runs out of RPMS.

The 2.47 is a bit too steep for the gear ratios of the 722.3 trans + OM617 turbo. In the city you have gears 1,2,3 and thats about it. Freeway 65 and over you can use 4th gear but don't expect much passing performance without dropping to 3rd.

We did this conversion on my dad's old 1983 300SD a long time ago.....it was ok....but mpg's only went up about 1mpg. For just crusing the highway at 75-80mph its nice because its quite a bit quieter as RPMS are more around 2700 instead of 3,500+

The vehicles with the 2.88 are a much better balance of performance to lower revs
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'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
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  #5  
Old 09-12-2019, 10:31 PM
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Mileage will suffer in city driving,improve marginally at hwy speeds.Low RPM in town drops the RPM out if the tourqe window.That window is where you will achieve best mpgs.I also understand not all folks are chasing mileage,and lower noise levels are certainly nice if you spend a lot of time in your car.
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  #6  
Old 09-13-2019, 12:56 AM
vwnate1's Avatar
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Location: Sunny So. Cal. !
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Thumbs up

Thanx for this .

The video was poorly shot as the tachometer is almost impossible to see due to sun glare .

However, looking at the speedometer makes it clear that acceleration didn't suffer much .
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  #7  
Old 09-15-2019, 03:55 AM
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Join Date: Nov 2018
Posts: 1
I put a 2.88 in my '81 300D, but... I have a 4-speed gearbox and have much better control over the rev's and when I shift. My car has some mod's that the P.O. installed.

1. Garrett T04 turbo - it works but this is/was a non-turbo engine but it has plenty of power when you hit the power band.

2. 3-inch air intake with a cone filter. This is getting removed and replaced by a stock filter, housing from a W126. I just have to make an adapter for the larger turbo intake.

I take the car on 3 to 5-hour trips, at interstate highway speeds, on a regular basis. At highway speeds, there is a 15 MPH difference between what is indicated on the speedometer when compared to the GPS. 60 mph indicated = 75 mph GPS. This translates to 33 mpg (NO A/C Running) and 29 mpg with the A/C.

I did install a complete engine coolant system from a W126 for a little extra capacity so temps are not an issue. One day I will to a top speed test... maybe...
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  #8  
Old 09-15-2019, 08:35 PM
pawoSD's Avatar
Dieselsüchtiger
 
Join Date: Oct 2004
Location: Grand Rapids, MI
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Quote:
Originally Posted by vwnate1 View Post
Thanx for this .

The video was poorly shot as the tachometer is almost impossible to see due to sun glare .

However, looking at the speedometer makes it clear that acceleration didn't suffer much .
Acceleration does suffer, I'd say in a flat out run you'd lose probably 2-3 seconds.....and when trying to accelerate from a stead speed to a higher speed, its laggy as well due to the tall gearing.
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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)
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  #9  
Old 09-15-2019, 08:58 PM
Diesel user
 
Join Date: Jul 2018
Posts: 39
Maximum speed with this engine on completely flat ground is around 110-115. It has gone faster, but it had to have been on a slope. I wouldn't say that the acceleration is that much slower. I have raced a stock 300SD W126 and was a good car length ahead, but that car still had a "tamper proof" ALDA and stock boost setting with no hint of smoke. Floored mine was a little hazy with 13psi.

Apologies again about the poor video quality, one of these years I may have to buy a real camera. The 1st and 2nd acceleration videos were on a downward slope, so they are faster than the flats (not much flat around here) and were from a rolling start. You can hear one of the back tires chirping on the 2nd video going round the corner under power. The aim was to show the max speed ranges for the gearing, I was making a video of the last drive of that car which is now retired after serving me very well. I bet that the 2.88 is a little more desirable, but the 2.47 seem to be easier to come by in the yards, or it was years ago.

The replacement W126 I am building will have a 2.47 LSD from a 560SEL, that one may be way too low for the OD 5-speed box... will have to make a new thread about that down the line and let you all know how it goes.
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  #10  
Old 09-16-2019, 11:35 PM
t walgamuth's Avatar
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Join Date: Apr 2005
Location: Lafayette Indiana
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Quote:
Originally Posted by wschotty View Post
Maximum speed with this engine on completely flat ground is around 110-115. It has gone faster, but it had to have been on a slope. I wouldn't say that the acceleration is that much slower. I have raced a stock 300SD W126 and was a good car length ahead, but that car still had a "tamper proof" ALDA and stock boost setting with no hint of smoke. Floored mine was a little hazy with 13psi.

Apologies again about the poor video quality, one of these years I may have to buy a real camera. The 1st and 2nd acceleration videos were on a downward slope, so they are faster than the flats (not much flat around here) and were from a rolling start. You can hear one of the back tires chirping on the 2nd video going round the corner under power. The aim was to show the max speed ranges for the gearing, I was making a video of the last drive of that car which is now retired after serving me very well. I bet that the 2.88 is a little more desirable, but the 2.47 seem to be easier to come by in the yards, or it was years ago.

The replacement W126 I am building will have a 2.47 LSD from a 560SEL, that one may be way too low for the OD 5-speed box... will have to make a new thread about that down the line and let you all know how it goes.
You'll probably be fine. You'll have to pull it out of fifth for modest hills but you should be able to top 45 mpg highway, IMHO....running 60 to 65.
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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.
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  #11  
Old 09-16-2019, 11:37 PM
t walgamuth's Avatar
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Join Date: Apr 2005
Location: Lafayette Indiana
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Quote:
Originally Posted by Garagefull View Post
Mileage will suffer in city driving,improve marginally at hwy speeds.Low RPM in town drops the RPM out if the tourqe window.That window is where you will achieve best mpgs.I also understand not all folks are chasing mileage,and lower noise levels are certainly nice if you spend a lot of time in your car.
I've run tall gears and not noticed any fall in town mileage.

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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.
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