5 Speed

[Harry Moon]

has any one tried putting the CCKW 5 speed in a CMP?

[jim sewell]

The bolt pattern , the input shaft and the clutch spline will be ok but the trans will be longer .
In a 2 wheel drive you would need to shorten the tailshaft and find an alternative method to show vehicle speed ( no speedo drive on CCKW box ).
In a 4 wheel drive it becomes difficult to shorten the tail shaft to the trans case.
Not sure whether the cross member will require modifying .
Regards
Jim S.

[Phil Waterman]

I don't have the ratio for the different boxes in front of me but years ago I discussed this with a CCKW expert (define as anyone who is crazy enough as to own ten or more CCKWs) at the time he and I were both running stock engines. We did a lot of traveling together here in New Hampshire (lots of hills) and neither truck seem to have a real advantage in speed or hill climbing. The four speed vs the five speed just meant that we shifted gears at different points.

So before the effort of changing the gear box take a look at the ratios. Some place I have an RPM vs torque curve for the CCKW engine and the 216 which would also be interesting to compare.

My CCKW expert said what you really want is a box with a 5th over. I'll send him this thread and see what he has to say.

Cheers Phil

[Lang]

Phil,

I think you are right when you say what is needed is an overdrive box, not more gears.

Assuming the 216 has enough power to pull an overdrive ratio on normal flat roads with a bit of a headwind (it certainly will be requiring a lot more shifting regardless, over the current 1:1 ratio on gentle rises) the ideal would be a box still having the current 1:1 ratio with an overdrive on top of that.

If you are going to put a non-standard box in why mess around with big heavy GMC boxes when you can have a delightful light modern overdrive box with full synchro.

Regarding the advantage of more gears. Mack produced a sales video some years back to demonstrate what gears truck operators should have for their operation. They had two identical Mack semis, fully loaded at the bottom of a very long hill climb. The only difference was one had a 5 speed box and the other a 13 speed box.

In the drag race the 5 speed truck won by miles as it maintained momentum for longer against the periods of loss of drive suffered by the continuous changes of the other truck. In the next race the 13 speed driver jumped 2 gears at a time and although he still lost he was much closer.

They then went out on to the mid-west plains with gentle rolling rises along the freeway. In this case the 13 speed truck maintained much better speeds and returned lower fuel consumption because it always had the fine adjustment of just the right gear.

An overdrive on the CMP (if the engine can pull it) is the go. Of course putting bigger diameter tyres on has the same effect. Just having more gears in our old vehicle situation is pointless.

Lang

[Phil Waterman]

Heard from my CCKW friend he also pointed out that the trany is taller which would create a clearance problem with the floor.

Also found the Dyno info on the web on 40-50s vintage Chev 6 cylinder truck engines. http://www.ssrfanatic.com/forum/f5/j...uggesti-26664/

Normal found information on the web disclaimer, NO GUARANTEE OF ACCURACY, but interesting.

[Harry Moon]

.... that the CCKW Trans had an overdrive. Did any of them? I agree no point if it doesn't have an O.D.

[Lang]

Harry,

You are right.

GMC Box First 6.06 to 1
Second 3,50 to 1
Third 1.80 to 1
Fourth 1 to 1
Fifth .799 to 1
Reverse 6.00 to 1

All this is still just a moot point because you have transfer case ratios
(on all multi drive vehicles but below is for 6X6 GMC)
High 1.16 to 1
Low 2.63 to 1

Axle ratios 6.6 to 1

And tyre diameter which can easily change the on-road total ratio by 10%

When you are considering dropping down the engine revs during cruise (to make it quieter and less engine stress plus better fuel consumption) there are several ways. You can change any of the above to achieve the aim.

In order of ease and cost:

1. Easiest is to put on bigger tyres, but may not suit originality appearance requirements.

2. Higher ratio crown wheel and pinion in diff.


3. Overdrive gearbox.

4. Fit a 235 engine which will still scream and use fuel but can be safely run at higher rpm for long periods to give you the extra cruise speed.

Lang

[sapper740]

Originally Posted by Harry Moon

.... that the CCKW Trans had an overdrive. Did any of them? I agree no point if it doesn't have an O.D.

Harry, I take it by your question that you are looking for a little more speed and/or lower engine rpm? Possibly for the runs to and from Kelowna? Rather than spend a lot of time and money altering your CMP by retro-fitting a CCKW or any other transmission for that matter have you considered any of the many available bolt-on electrically operated overdrives? I seem to remember back in high school my friend's Humber had such an overdive...a Laycock de Normanville unit if memory serves me correctly. In the modern era, there are many heavier duty after market overdives available for RV's which became popular when fuel prices began to rise. Although it would require shortening of the drive shaft, it would leave your truck original and cost less than a tranny swap. Something to consider. Derek.

[Harry Moon]

I'm not going to put it in my C15A, as it runs real well with the 235 and now the 10.50 16's from Wallace Wade.
I might add a flexible aluminum fan but that is about it for mods. I've put almost 13,000 km's on it so far.
No, what I've got now is a recently rebuilt 270 and tranny from a CCKW that I'm going to put in iether a C60X or the C60L in my driveway.
If I do the C60L I'm thinking of putting the differentials out of a C15A on it to again get some safe highway speed into it. I might want to take it on a long drive.
Comments welcome on the pro's and con's of the 270 Vs. a 235

[Alex Blair (RIP)]

Originally Posted by Harry Moon

I'm not going to put it in my C15A, as it runs real well with the 235 and now the 10.50 16's from Wallace Wade.
I might add a flexible aluminum fan but that is about it for mods. I've put almost 13,000 km's on it so far.
No, what I've got now is a recently rebuilt 270 and tyranny from a CCKW that I'm going to put in either a C60X or the C60L in my driveway.
If I do the C60L I'm thinking of putting the differentials out of a C15A on it to again get some safe highway speed into it. I might want to take it on a long drive.
Comments welcome on the pro's and con's of the 270 Vs. a 235

Hi Harry..
The 270 is too long for the C 60 L but the 235 will fit in better..
The C 60X is set up for the 270 and will fit right in..Notice the extended grill section on any C60X ..
I guess anything will fit in anything else,but why suffer if you don't have too..

[Harry Moon]

Originally Posted by Alex Blair

Hi Harry..
The 270 is too long for the C 60 L but the 235 will fit in better..
The C 60X is set up for the 270 and will fit right in..Notice the extended grill section on any C60X ..
I guess anything will fit in anything else,but why suffer if you don't have too..

I actually heard about the extended grill but haven't actually had a first hand look at one that was still in one piece. I took some pictures of the front mount on both trucks and was wondering what I might have to do. Is it a case of the radiator having to be moved forward or the front motor mount or both. I noticed on the C60X that the rear mount is different in that it is not actually a crossmember but 2 seperate brackets on each side.
Those manuals I got off you Alex at the start have been real life savers but I don't have the C60X Books. Are there any good pics that really illustrate the differences?

[Matt Baker]

Gday Harry , i Have a cckw box in my c15 blitz wireless van and it is great on the road it keeps up with jeeps very well .

It was already fitted when i bought the vehicle so cant help out with details of the conversion but it has no speedo so i have to keep a sharp eye out for speed cameras.

Cheers Matt Baker.

[Harry Moon]

Originally Posted by Matt Baker

Gday Harry , i Have a cckw box in my c15 blitz wireless van and it is great on the road it keeps up with jeeps very well .

It was already fitted when i bought the vehicle so cant help out with details of the conversion but it has no speedo so i have to keep a sharp eye out for speed cameras.

Cheers Matt Baker.

That's great news. The speedo on A's L's and X's runs off the transfer case so I should work that out OK.
Since yours is, I assume a 4X2, then it was just a case of shortening the driveshaft.

[Harry Moon]

... if in fact the trany I have is an O.D. in 5th? I don't even have a shift pattern.

[hrpearce]

Harry find 5th gear then chalk the top of the imput and output shafts, turn the imput shaft one full revolution if the output shaft turnes past one revolution then it is OD.