Gear ratios & highway speed

[Lang]

If you took out the front axles (should not need 4WD on this trip) it will improve things tremendously in the fuel consumption/noise/vibration/steering departments. Just disconnecting the drive shaft still leaves you turning over all the axle/diff machinery. If you want to go one step further you could drop out the transfer case for another 50% reduction in gear noise and get a prop shop to make a straight drive shaft.

Not a big job to change diff ratios and probably easier and cheaper than fitting other gear boxes. Half a day at the diff shop and drive away.

If you are going to fit a 5 speed gear box you would be better off with a Toyota Dyna box instead of a big clunky agricultural GMC box. Changing a gear box sounds simple but once started you chase your tail because the new box needs new mounts, gear stick hole has to be changed (and sometimes floor humped), tail shaft length may need to be altered etc.

Lang

[lynx42]

Peter,
Good luck with the the Legacy trip. I think that is wonderful. If your passing my way there will be a bed available if needed. We could also join your trip for a few Km in our area to help promote the cause.Maybe all Australian MLUers can join for a while along the way as well.

An axle set from a C15A fitted with 20" wheels will be the easiest way to up speed the C8AX. The C15A has 8 stud wheels against the 6 of the C8AX. If you had a spare set of 6 stud centres you could also weld 20 inchers onto them but I guess they are pretty scarce on the ground.

Good Luck and safe trip.

Regards Rick

[cletrac (RIP)]

Older truck type 5 speeds usually aren't overdrives so won't help. Some newer small ones like the T10 would take a lot of work to make them fit but could be done.
The C8A uses one ton rear ends so different ratios might be available. Modern 16" tires are available in quite a few sizes and it shouldn't be too hard to find some bigger diameter tires. They fit the rims and as a bonus you'll get a lot quieter and smoother ride. 4 inches more diameter cuts engine RPMs by 20 %.

[Phil Waterman]

Hi Peter

This issue of more highway speed has been touched on before here is a link to some of them https://www.google.com/search?q=%22H...i&cr=&safe=off

Now on to some of the points that I have experienced in 33 years of driving a 101wb HUP and some 20 years of driving 134wb C60S.

The 20" wheels with 1100x20 tire sould definitely get you up to highway speeds of 60 MPH on the flat with the 216 engine. But I'm not sure the 216 will be happy with sustained driving at that speed for 15,000 Kilometers or nearly 10,000 miles. Remember that your distance target is over the rebuild distance for the engine, though your miles should be cleaner and mostly highway.

Reason I say the C8AX will do 60 MPH is that my C60S with its original 216 engine would pull down the interstate at indicated 50 MPH and corrected road speed of about 60 MPH (rubber overdrive) suspect that if you run military tires you will be replacing them about halfway through your trip.

Once drove my C60S leading a convoy with my foot planted on the floor, never shifting, for an entire morning top speed 65 MPH running away from the JEEPs on the down grades and down to 35 MPH on the hills. On other long convoys the CMP didn't seem to mind it as much as the CCKWs. You could always touch the transmission and transfer case of the CMP with your hand and not get burned, you could not say the same for the CCKWs.

When I up engined the C60S to a 261 it will pull away from most convoys if I want has more speed than I can use. Which brings us to another speed issue with CMPs particularly the 101 and 134 wheelbase they get very lively at speed, think you will find that 60MPH is about tops.

Next noise and vibration, good noise canceling headset with an intercom to talk with anybody riding with you will be essential. Drive train vibration will be something that you will discover for your particular vehicle there will be speeds that everything vibrates and speeds that things seem happier.

I did drive my HUP for an entire year with both of the front inner axles removed. Which did improve fuel economy and reduced the noise. With the axles out the front end is not turning the differential or front drive shaft.

If you go this route I would have your rear axle shafts magnafluxed to look for a problem right at the end of the spines.

One more suggestion get a infrared thermometer and make yourself a temp chart for all the critical points. Then check the temps at the end of the days run. May really help spot a problem in the making before it becomes a trip stopping break down.

[Richard Farrant]

Something else to think about, and I don't think has been mentioned, is raising the gearing with bigger wheels is fine for top speed, but it will mean higher ratios in low gears, and any hills may be more difficult, as the 216 is not blessed with a lot of power, I run a 28hp Bedford (72bhp) and is the British version of a 216, so know what this is like.

[Lang]

Richard,

First gear on the small CMP's is so low many people do not use it in everyday driving, I think that would not be a problem with upgraded final drive ratios. With any raising of gear ratios you certainly will have to change back earlier on hills but if Peter does not get too greedy and have to change down on the flat into a headwind he can drive normally.

Pete,

As for putting 20inch wheels on the vehicle in question it would dramatically change its appearance and make it look hotrodded. I have upsized the tyres and wheels on a lot of military and non-military vehicles over the years mainly to run on sand and without exception, on good roads they reduced road vibration but ALL handled and steered like c..p!

Taller 16 inch tyres are available but ANY of the above gearbox/diff suggestions would be cheaper than buying these in Australia. I have been trying to source some for my 4WD Mitsibishi Canter and find the very few brands available all add up to $2-3,000 for a set.

The modern Michelin radial equivilent of 9.00x16 which will fit your wheels are between $500 and $700 each depending on your source! The cheap and readily available MRF 9.00x16 non-directional that I have on my Dodge WC53 have done nearly 10,000km (much of it flat out on the highway going to and from Corowa) and all have over 80% tread remaining. A new set will get you around Australia easily. You might do some sums on getting tyres from Coker and others in USA but I doubt it will be an economic success.

[Phil Waterman]

Hi Peter

You started your thread "Ok - I know I'm going to get crucified for this but here goes!". But not to worry, most if not all of us have wanted to take a really long trip in our CMPs and are either envious or doubt your sanity (my kind of crazy) for undertaking a trip of that length.

I'd love to do the Alcan tour in 2012 but the distance to and from the start is to long to consider for my old bones. I suspect the C60S would make the trip fine.

Hope that you can workout all the details, carry a good video camera and still camera so that you can share the trip.

Hope you will keep asking questions and bouncing ideas of the rest of us.

Cheers Phil