Bigger tires...go faster?
- Thread starter sharkbait73
- Start date
thebigblue
Adventurer
EU (German) truck speed limit is 80 km/h (49.7 mph), but common speed is 90 km/h (56 mph) because that's what the truck speed limiters is set to
A few trucks and buses will be at 100 km/h (62 mph) on motorways.
I travel at 80 km/h on highways in my 1979 MB L608 and is often overtaken by trucks doing 90 km/h. I find 80 km/h to be sufficient when on vacation, I'm in no hurry and want to relax.
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charlieaarons
Explorer
Remember that most large tires are rated and safe only up to 90-100kph unless you run 395/85R20 Michelin XZL2 (110kph) or 14 ply Goodyears (130 kph).
sharkbait73
Member
That's great! Thanks for all the input Folks!
Grenadiers, I like that you've posted your max speed for other drivers
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Grenadiers, I like that you've posted your max speed for other drivers
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Sitec
Adventurer
Sooooo, I learned of something here in Australia that might be a relatively cheep way of gaining more speed for us that need... I helped out a local MB mechanic who looks after a fleet of Mercedes Benz NG's, MK and SK's. He needed o rings and I had what he needed saving him a drive. Anyway, he tried to give me some $$$ for these O Rings, and I said 'nah, don't worry about that, you are my Merc Truck advise man'! He smirked and said no prob.. The conversation continued and we got around to the fact that my truck is flat out at just over 90kmh. I asked how much work it was to 'speed up' the HL7 axles I have... He said "a lot of work, you need a Joey Box". I'd never heard of a Joey Box before but a few years ago it was common to add a small in line 'Joey Box' behind the main box and in front of the rear axle to give older trucks a higher top speed, and also a low box if a 3 speed Joey was specified. I think I have got my hands on a Joey in exchange fore a carton of beer, so will keep you updated on the logistics of what ratio it is, how reliable it will be and the possibility of fitting it between my gearbox and transfercase.
sharkbait73
Member
I've never heard of either term...but that is not surprising! 
Let me know how it turns out Sitec
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Let me know how it turns out SitecSent from my Pixel 2 using Tapatalk
charlieaarons
Explorer
No. I have one in my garage. It is a 3 spd gearbox. Ratios like 2.00, 1.00, 0.73, selected by a shift mechanism.
VerMonsterRV
Gotta Be Nuts
Count me in on the interest in this. On a related note (the power for the different gearing), we have an OM366LA 204hp engine. Anyone know the difference between the 204hp and the 240hp variant? Is there any difference in the internals or is it just a larger turbo and injector settings?
Neil
Observer
I like this idea. The only problem i can forsea on my vehicle is actually fitting it in . The shaft from my gearbox to transfer box isnt very long . Maybe 800 mm inc the universal joints. Doesnt leave much space.
Moving the transfer box back is doable but lots of work .
If it has a nuetral position then i would look to putvit between transfer box and rear axle as this device would only really be needed for 2 wheel drive on the highway.
In 4 wheel drive it could be set to nuetral and all would return to normal. If it has a nuetral.
Still watching
Neil
Moving the transfer box back is doable but lots of work .
If it has a nuetral position then i would look to putvit between transfer box and rear axle as this device would only really be needed for 2 wheel drive on the highway.
In 4 wheel drive it could be set to nuetral and all would return to normal. If it has a nuetral.
Still watching
Neil
Sitec
Adventurer
Yes, from what I have gleaned in a few phone calls yesterday they are usually 3 speed, underdrive, direct drive or overdrive, and can be operated by a bowden cable or an air ram. The one I looked at yesterday was short enough to go between my gearbox and transfer case. The link shaft is only 610mm long but the boxes I've seen are less than that. Problem is the shaft faces on the gearbox output and transfer case input are about 100mm out of line!
LostInTheWorld
Builder/Traveler
That is interesting. On our U1300L, the shaft between the clutch and the transmission is actually pretty long. I bet something like that would fit.
Michael
Michael
Neil
Observer
What torque can these things handle. If its between the gearbox and transfer box its going to get some serious torque in the lower gears. I think its best place is between transfer and rear axle. Obviously its only good for 2 wheel drive snd ideally would be best in the higher gears eith less torque
Neil
Neil
Sitec
Adventurer
This is my reservation with the Joey Box... which is why I plan to do everything between the main box and the transfer case. I can then carry the original link shaft with me, and then when the Joey explodes I just put the original shaft back in!
I'm not really interested in the low gear option as our trucks are not rock crawlers, and am only really interested in the overdrive option for long journeys.. When off the freeway the box would be in 'direct drive' gear, and in theory this is a straight thru dog coupling so should take the same load as the shaft the joey box replaces. I have access to one locally so might just grab it and pull it apart for the sake of learning and this thread!
