Wheel Drive Gears - for lower RPM at highway speeds

[TechMOGogy]

Has anyone thought about having new wheel drive gears (#20 and #7) made?
I know with the Haflinger there are 4 sets 52, 58, 64 and 75km/h
Thought is to make a new set so that ultimately you would have a higher top speed but use would be to still drive around 100km/h but have lower rpm. No clue how to do the math on something like this :?:
Obviously you would loose some low end gearing
Just thinking out loud

Dan

[ako]

To reduce RPM, you would need to make item #7 bigger and #20 smaller.

The question would be how much space is there in the housing for #7 to get bigger. Milling out extra metal from the casing would not be advised. I haven't pulled my apart yet so I don't know the clearances.

Plus you would need 4/6 sets depending on 710/712. Would not be a cheap exercise, but maybe outsource to China? A group order would help but who wants to be the guinea pig?

You would want to use a high grade of steel and then heat treat afterwards.

Making #20 smaller may also have an effect on the oil level required in the hub. Again only guessing here because I have not studied the design in detail.

Anyone have a photo of the other end of item #1 after being opened up?

[Jimm391730]

Simpler to use a 710 transfer case in a 712, or a TD tranny. It is not recommended to do both, this gears the truck much too high (and some consider the TD tranny too tall in gearing as well).

[ExpeditionImports]

Not much room in those portals and very expensive to manufacture and then there is the validation, durability and reliability aspect.

FYI, if you have not seen these pictures before this is what happens when you park a truck in water for a couple of weeks (20"+ deep), then drive without changing fluid.

712M Reynolds Backing Plate Removed 1 Hub Seal Leak (35).JPG (853.78 KiB) Viewed 8550 times

712M Reynolds Hub Seal Leak (37).JPG (755.3 KiB) Viewed 8550 times

[ako]

No clue how to do the math on something like this :?:

Item 7 has 15 teeth. Item 20 has 34 teeth.

The ratio is 34/15 = 2.26666. A quick check on goatwerks technical page confirms this.

Using the image Scott put up, I would say you are only going to get 1 extra tooth on the drive pinion.

So for the sake of simplicity let use assume the new pinions are 16 and 33 respectively.

The new ratio is 33/16 = 2.065.

Comparing the new and old ratios :

2.266/2.065 = 1.097.

So you have a 10% higher speed or 10% lower revs. Plus 10% less torque.

As per above it sounds easier to swap transfer case or taller tyres.

[TechMOGogy]

Simpler to use a 710 transfer case in a 712, or a TD tranny. It is not recommended to do both, this gears the truck much too high (and some consider the TD tranny too tall in gearing as well).

It is trying to find a TD tranny that started my thoughts esp since the Haflinger has already done this.

[ExpeditionImports]

The TD manual transmission will require more power from the motor. Yes they are extremely difficult to find. Brian had a TD transmission in a 712 years ago and absolutely hated it. Might not be as bad in a 710. Required starting in 1st gear all the time and the 1st to 2nd shift pattern is unusual to say the least. 5th gear (OD) was for driving on a flat plate. If you spend the majority of the time on pavement then it might be OK but you are more than likely going to need more power to match the gearing. Toss in a loaded truck and I don't think you will like the overall package.

We have received speed questions a couple times a month for the last 15+ years for both Unimog and Pinzgauer. Will it go faster and how much? The newer Unimogs can go "faster" with an increase of maybe 5-8 mph top end for around $15,000 in addition to the truck price. Combination of tires, overdrive and power increase. For the Pinzgauer the price is a little less but the speed increase is not much more. Both applications require additional engine power. Remember you are driving a 25+ year old military truck the shape of a brick designed to travel convoy speed. The other side of the equation is parts are spinning in gear boxes designed 30-40 years ago which were never intended to rotate at these speeds.

We have convoyed Unimogs and Pinzgauer to numerous events all over the West. Whether it is a 600 mile drive to NWMogfest or a 1000 mile drive to Moab it is always the same. Take your time and enjoy the ride or use a truck and trailer. Just our experience.

[TechMOGogy]

No interest in going fast - been around these vehicles a long time.
Just seeing if there is a way to lower the RPM at 50mph - thats it

[David Dunn]

The TD trans goes better with the 712 than a 710 transfer case. The 716/18 transfer case is 6% lower than the 712's ( and no , it will not fit a 710 or 712 )
I too had a TD tranny in my 712 back in '02 and hated it, and if I hadn't sold the 712 would have swapped it back. People get fixated on the top speed at a lower rpm and forget about everything else. Besides a higher 1st gear, you lose 1 intermediate gear for the OD. You're you're whining the engine further in the lower gears just to get where you were with the original trans to reach 5th (4th in the TD trans).

[TechMOGogy]

Ok so the Haflinger (once again) has 4 different wheel drive gears
The Canadian model came with 75km/h gears
The Pathfinder model came with 64km/h gears
Others came with the other ratio's
Seems this is ok since the factory did it but all other ideas are taboo?
I understand that we have all seen 10,000 "How do I go faster" posts but that was not what I was asking.
Anyways, as I stated in my 1st post - it was just a thought.
Clearly not a good one in most peoples books so I will drop it.
Please don't bother with the "if you want that then you should buy a TD Pinz" as I have seen all those threads too.

Hey Andre - your TD in your 710m sucks, just ask and we will tell you

Cheers,
Dan

[Jimm391730]

Steyr apparently did not make any options to the hub gears. I think the above responses are just good food for thought in regards to your initial post about the feasibility - as AKO said, looks like it might be feasible to change 10% higher, but the cost/effort to do all four or six hubs seems high compared to changing the transfer case or transmission.

In my opinion, no one was slamming you for your question -- the results of changing the hub gears just do not look promising. "Not promising" is not the same as "taboo". Frankly I thought your question was interesting or I wouldn't have responded, it did make me think about it. And my thought was that swapping the transmission would be easier and less expensive, not necessarily better.

Personally I'd love to see an alternate transfer case with about 8-10% higher high range, and 15-30% lower low range. But that, too, has been kicked around ("kicked" being the operative word!) as it would take a whole re-design of the t-case to even begin to conceive of it. It's just not practical to retrofit the existing t-case shell, never mind an easy conversion!

Anyway, keep thinking!

Jim

[ExpeditionImports]

Must be some miscommunication since you are talking engine speed and the Pinzgauer makes the most HP (what little there is) at around 4000 RPM. In a stock configuration at 50 mph you are running between 3000-3250 RPM in a 710 and 3250-3500 in a 712 depending on tires. To maintain speed at 50 mph with higher gearing will be difficult with a lower RPM unless on the flat. Engine RPM is part of the equation but cannot be taken alone. The Pinzgauer motors make good torque over a good range but once you hit 3000 RPM the torque starts to fall off.

No offense meant just letting people know these trucks are pretty integrated in their design for what they were intended for. As an example a customer drove a 712 with TD transmission from Kansas to Denver which is pretty much a slight grade the entire way. With an empty truck he had to continuously hunt between 4th and 5th to maintain speed between headwind and grade traveling around 53-55 mph. The throttle response is softer with the higher gearing and takes longer to accelerate.

Just information.

[TechMOGogy]

Sorry - rough day back at work and crappy BBQ comp results = me taking everything negative.
Dan

[kdiqq]

I've worked with gear vendors before on different projects. The tooling for gears is pretty standard, the internal splines are trickier. All can easily be set up on a machine. I can help set up a spreadsheet to figure out what ratios you may want. From there it's pretty easy to ask a gear vendor what you want. The big advantage I see to this is the chance to go to much quieter helically cut gears. When running 4 or 6 piece runs, it may be costly but I'm advocate for the unique. If you need help doing the math behind it or getting drawings together, let me know. I have experience doing this and it's not as daunting as you think!

[Garrycol]

Having just been through the evolution of trying to get a little more speed for a little less revs in my Haflinger I know where Dan is coming from. In my case I went to 14" rims and 75kph hub gears and managed to ensure my improved engine does not go above rev line in 5th gear. Without giving the engine a higher rev range or expensive mods to the diff ratios or gearbox ratios there is not a lot else that can be done.

The first Haffys hubs were low geared and over the years as Dan has mentioned they went up to 75kph gears - as far as I am aware within the same hub castings - so maybe as Dan has suggested this could be done with the Pinz - the change in size if done to both gears not much of a change is needed. Unless things are measured up you never know so I think Dan's OP is fair and reasonable.

The points made about the engine pulling the gears is also important. Torque is more important than power and ideally at max cruising (not max speed) speed the engine should be at max torque - often in standard setups it is on the downward slope where going into an overdrive scenario engine revs may be back on top of the torque curve - but then maybe not.

I dont have a Pinz but I do have a 101 and wil I have more power and torque than a Pinz I am also a little bigger. I have the same issue as the Pinz - I would like to cruise at higher speeds - I have a high top speed at about 125kph but I am way off the back of the torque curve so cruise is about the same as a Pinz (80-90kph). I have the luxury of being able to fit an overdrive and change transfer case gearing and I have overdrive fitted.

My experience with the overdrive confirms the concerns about engines being able to pull higher gearing - with O/d selected the truck is a pig to drive in the mountains where I live - downhill is great - hills and headwinds are no good. However out in our flat sandy outback tracks when you drive slow the O/d comes into its own - top gear, o/d in sitting at 50kph engine at 1000rpm in its high torque range and just chuggs along with no throttle and great fuel consumption.

To address my issues I am going to change the 3.5V8 for a 4.6V8 with a cam that raises torque up to 4000rpm - low torque will still be good. I have my O/d and can change my hi range gears to an o/d situation but the new engine should pull this.

So back to the Pinz and based on my experience with the Haff and 101 - changing hub gears may help but without increasing engine torque the engine will struggle. I have not heard much about o/d on the pinz so I guess that is not an option. Changing the tfr case hi range gears (different model or purpose made) would be expensive and you have the same engine torque issue. Changing the tfr case to something like a Landrover LT230 which can take a O/d but not a realistic change for most Pinz owners.

So the only solution is some sort of selectable O/d that allows the engine torque to work as designed when needed in changing circumstances.

End result - leave things as they are with maybe bigger tyres and use the vehicles as designed. It is a shame that the designers of the Pinz did not design simple things into the drive train that allow changes to be made to meet differing circumstances.

Sorry for the long winded response.

Garry