OldIHC

Hi,
What is the difference between a synchromesh and constant mesh transmission? I know what a synchro is and does but aren't all forward gears in a synchromesh transmission in constant mesh?
And is a Select-O-Matic transmission an automatic transmission?
Also, it appears from the brochure pages that several different transmissions will fit the 345 V8. If I have a '69 1700 Loadstar 304 or 392 engine with a 5 speed, how would I know if its a T-35 or T-51? (truck made in Canada and no line setting ticket available). And will a T-35, T-51 and T-74 all interchange with my gas V8 or does each trans require its own unique bell housing? I might like to find a T-74 7-speed if it would work with my 5-speed bell housing.
Lots of questions ....
Inquiring minds would like to know ...
Thanks.

I think you should go to You Tube for an animated demonstration of how transmissions work.. Everything you need to know is on You Tube.

hi,
I think you did not understand my question ... as shown in the pic below, all the forward gears are always in mesh, although I know power only goes through the gears locked to the shaft by the shift rail ring. So my first question still stands - on the ordering brochures above, the difference between a synchromesh trans where the gears are always in mesh, and a constant mesh transmission - just never heard of a trans called constant mesh before. And I can't find anything on youTube on the T-74 and/or its interchangability with the T-35 or T-51. I can't even find a picture of a T-74 on google.
Thanks.

OK, I get it now . . . but all you would have had to say is a "constant mesh" trans doesn't have synchroes. The name really has nothing to do with the mesh of the gears as all transmissions' gears mesh. If the brochure had called them either syncromesh or non-syncromesh transmissions would have been more self-explanatory to me.

https://www.edmunds.com/car-technology/ ... asics.html

This explains it pretty well.

There ARE synchro-equipped trans without first gear being synchronized. It was the first step after sliding-gear transmissions.

Thank you, I appreciate your reply.
It's not how they work that I don't understand, its just the terminology used to label their type of working I did not know. I don't recall non-synchronized transmissions as ever being labeled "constant mesh" transmissions. I just always called them non-synchronized transmissions.

Sounds like another vibration dampner/ harmonic balancer thing, to me.
Not THAT much going on inside a manual trans for there to be yet another label for them.

Yes, that's exactly what it turned out to be . . .