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Sync/Non-Sync - we are lost. The truck shifts into 1st (no rolling) just fine. There is a bit of granny hop sometimes in getting the clutch just right. 2nd up shift, 3rd up shift no problems. The first issue is on the downshift from 3rd to 2nd - nothing but grind until you get down to a crawl. Is this the need for double clutching?? You cannot get into 2nd gear on the downshift at cruising speed. At the crawl speed of 5mph, you can get into 2nd and then rev the engine and keep her rolling. I have suspected a trans issue between 3rd and 4th, but we haven't taken the truck out of the sub to check that.

You really should master the art of double-clutching. With modern, full-synchro transmissions, it's not really necessary, but it's a good skill to have anyway. With older transmissions, either "crash boxes" or partially synchronized, it's a must. The partially synchronized transmissions in our trucks will still work quite well with the synchros gone, but you have to know the "art."

The proper technique has been explained on the forum before, so just do a search for "double clutching" and you should find it.

Why were the transmissions partially synchronized ? Was it just the technology of the time or was it for a purpose?

Lifer - the last double clutching I had done had nothing to do with driving a M37....

So what we had is normal - downshifts require double clutching. Thanks!

Been there, done that, double-clutching wise!

When it comes to double-clutching an M37, it's less strain on the vehicle and the driver to do it going up as well as down. Once you get in the habit of doing that every time, you'll be well on the way to actually knowing how to "drive."

When you master the art of shifting a "crash box" up or down without using the clutch at all, THEN you can claim that you "know how to drive." It's not something that I would recommend doing, actually, but I've done a lot of it over a period of many years. (I refuse to say how many.)

Lifer - did a search and couldn't find a good thread - any help? Zach has been practicing around the block. Got good upshifting 1-2-3-4. No problem downshift 4-3. We tried the clutch, then out of 3, wait, clutch, try into 2 - grind......

Then we clutched, out of 3, clutch, brake to slow down, then at around 5-8MPH it will go straight into 2 without clutch? Obviously matching the vehicle speed down allowed us to pop it right into 2 with no clutch. Seem about right?

When the cluth is released you have to bring the engine rpms up to match approximately rpms the engine would be at if it were in gear at that speed. Then while maintaining that rpm, press the cluth in and down shift.

The general idea is to get all the parts inside the tranny spinning at the correct speed to mesh when you downshift. It's an art but it's not very difficult to learn. It takes a bit to master, though.

If you are in third gear and want to downshift to second: Press in the clutch and shift into neutral. Release the clutch. Give it some gas to increase the engine speed (and tranny speed since you're in neutral with the clutch released) to the approximate rpms you would be at if it were in second gear at that speed. Press the clutch in while maintaining the engine rpms. Downshift into second.

That is a generic description. I'm sure each person does it different but that should get you the idea.

Corey

My first question is at what speed are you down shifting from third to second? The way I do is to first apply brake to slow truck wheel speed than ingage clutch shift from third to neautral release clutch give some throttle engage clutch shift to second release clutch You should notice an increase drag on the engine but no lug. The key is speed both wheel speed and engine speed. If wheel speed is too high before down shifting than you will need to slow down.