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.