Wheel Drive Gears - for lower RPM at highway speeds

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ExpeditionImports
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Re: Wheel Drive Gears - for lower RPM at highway speeds

Post by ExpeditionImports »

Interesting comment in regards to helical cut gear versus straight cut gears. Historically the Unimog has been thru this before with the early hub reductions being helical cut gears. 2010, 401, 411...... In later models 406/416 on up they actually shifted away from the helical to a straight cut. The reference being that straight cut were stronger than the helical. That being said, I will confirm that axle noise is quieter on the 404 with the helicals than the later Unimogs.

Cheers,

Scott
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Hotzenplotz
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Re: Wheel Drive Gears - for lower RPM at highway speeds

Post by Hotzenplotz »

Folks

Imho the straight gears vs helicoil gears discussion will lead nowhere. There is no point the axial forces resulting from helicoil gears can be taken over. And you would have to modify 4 or 6 locations per vehicle.

Try to tackle the beast "centrally"

If you want an "overdrive" why don't you simply use 255/85 x 16 wheels ?
I have installed the 710 hi/lo gearbox in my 712, and now it merrily does 105 km/h on flat ground.

Another option would be a modification of the gears for 5th in the main tranny.

A discussion in a german Pinzgauer forum lists several other vehicles with the same ZF gearbox, but different ratios
http://pinzforum.kiruna.de/viewtopic.php?f=4&t=2612
Maybe the set of gears can be taken from them...
Cheers
Albert
========================
My Pinz has NEVER been with any army
kdiqq
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Re: Wheel Drive Gears - for lower RPM at highway speeds

Post by kdiqq »

Helically cut gears can be every bit as strong as straight cut gears, but you take on a big 'comfort' cost when using them. The only big advantages to helical vs straight cut gears are noise and improved wear. Even then, straight cut gears wear very well. Helically cut gears do apply a translational force when in use though. Once you figure sizing and pitch, you can calculate this though. I don't see helically cut gears being a problem in the Pinz hub, this translational force is relatively small.

In regards to the modification of 5th, it is not possible. 5th gear in the Pinz is a 'direct drive'. There is no 5th 'gear'. It's easy to describe when looking at the transmission diagram in the service manual or the parts diagram. What is possible is overdriving the transfer case further. I had a short thread on it. Still trying to source a transfer case. Andre said he has one that he is pulling out once he sources a TD transfer case (I think). I've worked through the design and ratios I'd be looking for and sent off my idea to a few gear vendors. Nothing can be set in stone though till I have gears in my hand. The advantage to this design is that in road range, you use it like a normal overdriven 5 speed (start in 1st). But in low range, everything is unchanged. You get all the offroad-ability the Pinz came with and, unlike the overdrive unit, you don't have to worry about it breaking in reverse. Hopfully this spurs some interest. I know that one set of gears will cost me a fortune, but if I can get a few pieces run, it would bring cost down significantly.

Pipe dreams for the time being though. I have other work on the Pinz that needs to be done before I can dedicate money to this. Here is the thread as an FYI. http://real4x4forums.com/PinzgauerBBS/v ... =13&t=9767

Scotts right though, you have to be very reasonable about the 'overdriving' you do in a Pinz. You can drop RPMs some, but there is a balance between running part throttle at a high RPM and running WOT at a lower RPM. You may not see any long term advantages if you gear up too much.
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Jimm391730
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Re: Wheel Drive Gears - for lower RPM at highway speeds

Post by Jimm391730 »

Even the TD tranny has a 1:1 'direct drive' in fourth (compared to 5th in the gasser tranny). In the TD, one of the other four gears is an overdrive. While I have a TD tranny, the overdrive ratio is higher than I would like and then instead of four gears below direct drive there is only 3, so the gap between them is larger. I do have a 2.7l conversion with modified cam and pistons so it makes somewhere in the 20-30% more power range than the stock engine, which helps considerably - otherwise I would not have enough torque at the lower revs. Then consider that my 712W weighs 8,000 pounds so losing the low range of first gear (5.33:1 in the stock tranny, 4.25:1 in the TD) makes a huge difference in offroad capability.

The Chrysler NSG370 is a six speed tranny, with a low of 4.47 and an OD of 0.84... both the OD and first are lower than the TD. These ranges (and the extra gear) would be a nice improvement over the TD tranny I'm using, but I don't have the skills to know if it is possible to mount up in a Pinz.
Jim M.
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Brickren
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Re: Wheel Drive Gears - for lower RPM at highway speeds

Post by Brickren »

Leave it to Scott to show us the most depressing pictures of neglect for our beloved. I bet it would be depressing to have a truck come in that has been either abused or neglected and to have to take it apart to see how bad it is. Thank you for the pictures, though, over the years. Its good to see what would happen if you did this or not do that. As an owner who.has tried various tasks and adventures over the past year, I always keep in mind what maintenance will be required afterwards. Brian.
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one2many
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Re: Wheel Drive Gears - for lower RPM at highway speeds

Post by one2many »

Some food for thought...the guy who did this with his Volvo used a mix of gears from the maserati bi turbo s5-18/3 variant and his 5 speed tgb20 gearbox and shafts and put it all together in the Volvo gearbox cases, he was however building a box to suit a diesel conversion. I think the shaft sizing in all the s-5/13 variants is the same...if so there is no reason this wouldn't work in a pinz box but I don't believe this would be a worthwhile exercise with the air cooled motor. As others have already stated it just doesn't have the torque at the lower RPM's achieved by an overdrive top gear...at best one would find themselves constantly hunting between 4th and 5th but probably find 4th being 1:1the most usable of the two. And I think the truck would be ruined for off road because of the changes and gaps in the first 3 gears.
For me it was just put some bigger tyres on and use it because it really does do what it was built for very well.

Scott nailed it when he said these trucks are very integrated in their design for what they were intended and that we should just use and enjoy them that way. We are all very lucky he finds the time to share the benefits of his experiences of these vehicles with us all...thanks Scott.

Not for me (why I bought a tgb 1315) but if one really wants the best of both worlds out of the aircooled pinz I believe you need to throw away its best attribute which is the very well designed, robust and simple air cooled motor (and its gearbox) and swap it for a compact diesel unit such as the 150hp merc om605td (with mech 602 IP pump) and 717.430 (or similar) 5 (or 6) speed, approximately 1300mm from fan to gearbox output. This is a whole different can of worms and off topic so I'm gonna leave it at that.
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1985 pinzgauer 712K factory 2.7lt civilian (RHD, 4 door K)
1979 Volvo tgb 1314a (under construction to om606 diesel/722.6 trans. Dual cab/tray)
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