I doubt that the transmissions in those trucks are the same as the transmissions in the TN vans.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Oh, I'm not suggesting that -- I'm just pointing out that Mercedes has before put constant-mesh boxes into vehicles that it was trying to make more "family-friendly".

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

I remember it being it being similar to other mb 4 speed trans in 2nd to 4th. Dogleg 1st is a big jump.

I only drive them a few times, you should ask someone like Kerry who owned a few.


.

__________________
1983 123.133 California
- GreaseCar Veg System

Correct. 2-5 is like a standard ratio 4 spd. It's a huge step down from 2nd to 1st.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Hey Jooseppi have you done the calculations for the W123 standard gear boxes and final drive differential ratios and compared them with your calculations?

Even 10 mph at 2000rpm seems a tad quick compared with my calculations for the standard set up - I don't reckon you'll be doing many hill starts (unless your nose is pointing down!) with that configuration.

Have you also been looking at the downshift characteristics? For example even if you manage 2000 rpm in top gear with out the engine stalling and you bump it down a cog - do you over rev the engine? (Probably not but is your proposed gearing useable - do you get what I'm saying?)

{I'm trying to find some estimations of power required to keep the whole thing rolling for you}

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Okay, I'm doing more math now... also, do you remember how many forward gears are synchronized? 2-5?

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Yeah, I get your point... I've already filled up a whole sheet with lots of equations (with small handwriting, and will need to start on another sheet soon -- I'll post more MPH/RPM numbers by the end of the day.

Thank you!

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Here's how far I've got. These are the specifications for a standard W123 with a non turbo OM617 fitted with the 4 speed and 5 speed manual gear boxes.

I don't have the ratios for the TN gear boxes yet

(Yes it is bloody snowing here again so I have the time!)

It is all in km/h (not old money).

Attached Files

Diff_gearbox_speed_calculations.pdf (99.6 KB, 134 views)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Attached below are five photos:

1) Here are the final, cleaned-up calculations and speeds in all five gears at 1000, 2000, 3000, and 4000 RPM. I assumed that I was dealing with a 6.14:1 first gear and used the first-fourth ratios of the 716.005/716.006 up to April of 1977 (picture five) as the second-fifth ratios (the third-gear ratio of 1.41 was simplified to 1.4). The calculations also assume a 2.24:1 differential, and a 24" tire diameter. I realize that I could have just multiplied the 1000 RPM calculations by two to get the 2000 RPM calculations, but I had estimated most of the final 1000 RPM numbers, so I wanted to get the 2000 RPM numbers, and then get the range of the 1000 and 2000 RPM numbers and multiply them by 3 for the 3000 RPM numbers, and by 4 for the 4000 RPM numbers. All calculations have been checked by a calculator, and I found one careless error early on, since corrected.

2, 3) I got the equations I used to calculate MPH at a given RPM from John Lawlor's Auto Math Handbook. I photographed a listing of the equations he gave in Chapter 13 ("MPH, RPM, Gears & Tires").

4, 5) I used the technical data book that Mercedes-Benz put out in January of 1980 to find the ratios of the 716.005/716.006 up to April of 1977 transmissions.

Please let me know if you notice any issues with any of my calculations/anything else. These gear ratios look workable to me, but I don't know how a diesel would behave with them (I've only driven gassers) -- please let me know what you think.

Attached Thumbnails

         

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

2-5 synchronized

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Oh, very good! How many are straight-cut/make a louder noise?

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

I've got more or less the same numbers as you now.

I've done a list with mph numbers for comparison. I'm using a 24.7 inch tyre that is a 195/70R14 specification tyre though here they are for both the standard W123 values and the possibly fictitious ratios on the TN gearbox

Please note I don't think that any of these estimated road speeds are actually achievable at the high ends in real life where you'd be battling against adequate power produced by the engine (especially an OM617) and aerodynamic drag and hills etc etc

I've yet to find the information I have somewhere that would give an indication if the OM617 would be powerful enough to rev past say 3000 rpm with a 2.24 differential ratio in normal circumstances. I don't think you've got much hope. (Assuming I've finally got my numbers right!)

Attached Files

	Diff_gearbox_speed_calculations_mph.pdf (99.2 KB, 120 views)
	Diff_gearbox_speed_calculations_possibleTN.pdf (96.8 KB, 141 views)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Those numbers suggest a problem. Top speed in my 409d van with the 617NA was around 68mph. It didn't have a tach but the engine was screaming at that point. Probably around 4000+ rpm's. Your calculations showing much higher speeds at those rpm's indicate that the engine would have a hard time dealing with average road speeds with that high a ratio differential.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I don't need to go past 65-70 MPH in my driving, but I would really like to reduce noise and boost fuel mileage -- that's why I'm interested in this. I would most likely dismantle the whole thing and re-install the automatic if I ever put it up for sale (unless, against all odds, it actually turns out!). Mine is a turbo, so at least I have that going for me.

...so I guess the one other way I could go is to buy a 5-speed w/ 6.14:1, and then try to find a 4.1:1 gear set to swap in (if that's even possible...).

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Well here's a chart showing how much power an OM617 should be making.

At about 2000 to 3000 rpm the power produced is between 46 and 70 kW => about 62 to 94 HP for the turbo OM617 when it is a NEW / GOOD engine!!!



In modern terms that isn't very much.

How heavy is your car?

Attached Thumbnails

 

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!