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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| Differential Gear Change.....changes
Martin,
when I change the gears to 1:5.28 in my 91 300GE we run into problems with the shaft seals. The EPC shows two seals but both were not available any longer. I can't find the pictures anymore, but Eurotruck found the right one - both are now combined into one single unit!
Also using new factory parts, the shaft details are just a bit different than the old ones - I had to use a new 'updated' crush sleeve..... see the picture.
Karl
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Attachments
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 IMG_2033.JPG (80KB - 3 downloads)
IMG_2035.JPG (90KB - 3 downloads)
IMG_2040.JPG (77KB - 3 downloads)
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martin
Veteran
Date registered: Apr 2006
Location: Del Mar, CA Isles of Scilly, UK
Vehicle(s): 99 G500 95 E300D 95 R1100GS 06 K1200R
Posts: 297
| RE: Differential Gear Change.....changes
Just in case other forum members are wondering what this is about ...
I asked Karl about the work he recently did when he changed the differential gearing in his truck. I just bought a 1984 280GE with stock gearing, stock tire size and a 5 speed transmission. I want to run larger tires, probably 33x10.50R15 on the original 15" alloys. The 5.88 ratio calculates to be the best solution, but I have a set of 6.17 gears.
(copied from Harald's 4WD site ... "As a rule of thumb you can expect to lose about 3.5% of torque/gear ratio for every inch of tire size increase.")
33" tire - 28" tire = 5" increase x 3.5% = 17.5% loss
4.88 gear x .175 = .854 + 4.88 = 5.734 ratio ... closest available ratio is 5.88:1
So I'm researching the advantages and associated costs of changing the gearing. I also need to assemble a parts list of what I'll need. Any help with compiling the list will help!
Seems as though several members here and quite a few from the MB forum (some have migrated here) have done this swap with good results.
Thanks. Martin |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Differential Gear Change.....changes
Martin,
I had the 4.33 gears in my G-wagen and after going to the 33" tires, I lost so much torque that my automatic transmission was shifting constantly.
Now with the change to 5.28 the G has enough power to take off in "D", acceleration is not bad, doing 65m/hr at 4000rpm - that's getting me around 4,8927Miles/Gallon 
The low range (Gelaendegang) performance is just great - but with the larger tires I'm increasing the stress/torque load on all drivetrain members!
Karl |
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hipine
Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
| RE: Differential Gear Change.....changes
.....but with the larger tires I'm increasing the stress/torque load on all drivetrain members! Karl Actually Karl, by changing the diff gears to suit the tires, you're minimizing drive line impact. If the tire size difference is immediately offset by a diff gear change, the loads on all drive line members upstream of the diffs are very close to just as they were before the changes. That's why you got your transmission performnace back to normal with the gear change. This is a very responsible approach to the desire for larger tires in my opinion. About the only things that see a higher load now are the axle shaft components and the brakes. -Dave G. |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Differential Gear Change.....changes
hipine - 1/31/2007 3:52 PM
.....but with the larger tires I'm increasing the stress/torque load on all drivetrain members! Karl Actually Karl, by changing the diff gears to suit the tires, you're minimizing drive line impact. If the tire size difference is immediately offset by a diff gear change, the loads on all drive line members upstream of the diffs are very close to just as they were before the changes. That's why you got your transmission performnace back to normal with the gear change. This is a very responsible approach to the desire for larger tires in my opinion. About the only things that see a higher load now are the axle shaft components and the brakes. -Dave G.
Yes, you are right Dave, the increased load is on everything past the new diff gears on the front and rear axles.
Karl |
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