transmission swaps

[Phil Waterman]

This topic comes up from time to time, but one thing I always wonder about is the matching the ratios of the transmission and axles to the peak torque of the engine.

While lowering the engine RPM in 4th gear over the road for the original 216 engine is kinder to the engine, without and increase in power don't really think any of the bigger CMPs are going to travel faster.

Has anybody matched up the ratios of the different synchronize candidates?

I saved the transmissions and bell housings from the 235 and 261 cubic inch Chevy engines I have. Both are synchronized transmissions 4 speeds.

Briefly considered going the full engine and transmission transplants into the C60L and C60S but the list of modifications concerned me as some of them require modifications to the trucks which I didn't want to make.

As mentioned the bell housings for the synchronized is different, engine mounts different, clutch fork location different, and of course the short shaft would get even shorter.

Matt with the CCKW in your C15 Radio Van which engine are you running? I didn't think the CCKW transmissions were synchronize so the advantage in that swap is the 5th gear?

Cheers Phil

[cletrac (RIP)]

Any of those older trannys will be 1 to 1 ratio in high gear. You have to get well into the 1970s to get a five over. Ratios in the lower gears wouldn't make much difference with everything that slow speed. If you use a non Canadian military bell housing the clutch fork sticks out on the wrong side so clutch linkage would be a nightmare. Those old straight cut trannys will last forever so I can't see any reason to make the swap.

[Matt Baker]

Gday Phil,

As far as i know my engine is a standard 216 but i was told a while back that it could be a splash 235 because it has a TR engine number but i am not too sure of this?

Cheers Matt

[Phil Waterman]

David

I have had good luck in converting standard Chevy left hand bell housing to CMP right hand clutch fork. With extra CMP bell housings being scarce I needed to convert a US Chevy NOS housing to accept the right hand clutch fork location. While the conversion is not as easy as converting an original CMP bell housing to left hand, the original Chevy bell housing were cast for either side and only the machining determined which side.

To convert a bell housing for the other side it is just a matter of carefully drilling and tapping for the clutch fork ball stud and cutting out the side opening for the fork arm. Alignment of the ball stud is rather simple with a couple of center bolts and compass the location can be copied from a CMP housing. In my case I used the very tired and very cracked housing from my C60L. Cutting out the rectangle for the fork arm is done by carefully drilling each of the corners then cutting between the drill holes, careful cutting don’t go past your pilot hole to prevent a cracking point. So as to take up the strain of the ball stud I made a tapered washer so that the lip of the ball was flatly grounded all the around.

If anybody needs more details I’ll post better pictures.

[Phil Waterman]

More pictures

[hrpearce]

Or if you don't have the tools for a conversion leave the fork where it is and use hydraulics.

[Phil Waterman]

Hi All

Robert's point is a very valid option Hydraulic slave cylinder will work. And if a different engine and bell housing may be the only practical solution.

I would love to see how they handled the widespread conversion of Chevys to Ford engines in North Africa that is mentioned in one of Bill Greggs book.

Now back to Chevys bell housing conversion time involved is at most 4-6 hours will be one of the major savings over conversion to hydraulic. The tools necessary to covert a Chevy bell housing from right side to left side are relatively simple and are as follows and.

Tools
1. Measurement bolts with heads cut off and spun in lathe or drill press to mark the center of the bolt end these are then threaded through the mounting holes on the bell housing measure with a compass to transfer the location to the new housing.
2. Drill hand or drill press
3. Drill Tap of the correct size and thread for the ball stud
4. 3” masking tape to locate the left side fork port and mirror to the right side confirm corners by basic measurements.
5. Air cut off saw to cut between the holes of the lever port – alternate to drill series of small holes to insert saw blade (slower but works)

One other point if at all possible replace the clip spring in the fork that hold it on the ball stud, these are available from many antique Chevy parts houses. These springs get tired after 60 years. When the springs are tired they tend to allow the fork to pop of the ball stud, particularly while you are adjusting the linkage.


Cheers Phil