TRL-107 gear ratios?

[Mark T]

1 hour ago, Geoff Weeks said:

Not the main shaft itself, but the gears that are on it are floating, the countershaft keeps them centered over the shaft.

Being "pretty sure" doesn't cut it. That is why I posted a picture from the Fuller Roadranger manual.

I have no idea on a Mack triple counter shaft trans, how they do it, Jo-Jo could chime in on that.

The main shaft except the nose (where there is a bushing between it and the input shaft, is splined the whole length with grooves tangentially for snap rings to hold the fore and aft position of the gears, The clearance between the gears and main shaft are maintained by the gears on the two countershafts. If the counter shaft or its key gets a twist, the gear on the main shaft gets out of line and it can be difficult or impossible to get into that gear. It is one of the 1st things to check on overhaul.

A bushing riding on a splined shaft would have an extremely short life.

Those splined gears on the main shaft are a very close fit to the splined part. Like enough for oil and that's it. Perhaps I should have used the word "bushing" as opposed to adding an (S)  Point is none of the mainshaft assembly relies on countershafts for support. It's a delicate balance in there of floating and not. If anything on a mainshaft does more than float as intended ???  you have problems. 

[Geoff Weeks]

Not if you look at the 1st picture I posted from the manual, that gear is going over the splines at quite and angle. Also there is no listing for the clearance of the gears on the shaft. The only listed clearance is for fore and aft float which is .005-.012 adjusted with spacer thickness.

If Glenn Akers was still with us he could settle this quickly. The main is held by a bearing at one end and bushing in the input shaft pocket. the gears are held located by the countershaft gears they mate with. They don't ride on the main shaft when the trans is assembled.

[Mark T]

7 minutes ago, Geoff Weeks said:

Not if you look at the 1st picture I posted from the manual, that gear is going over the splines at quite and angle. Also there is no listing for the clearance of the gears on the shaft. The only listed clearance is for fore and aft float which is .005-.012 adjusted with spacer thickness.

If Glenn Akers was still with us he could settle this quickly. The main is held by a bearing at one end and bushing in the input shaft pocket. the gears are held located by the countershaft gears they mate with. They don't ride on the main shaft when the trans is assembled.

I'm pretty sure the gears on the mainshaft are splined inside and ride the mainshaft. It's all pretty tight.  Floats, yet tight. Not a clearance that can be adjusted like the limit washers for fore and aft.  More like good or bad. The mainshaft shares a common centerline that also isn't adjustable. Good or bad. Bearing on the input, bushing between (input) rest of the shaft and bearing where it goes into the auxilury drive.  All floats, but it's tight. Doesn't rely on countershafts to give support in any way. 

[Mark T]

Then there's another bushing like that in the auxilury after the auxilury drive. 

[Joey Mack]

in the Mack transmissions, the speed gears have 2 thrust washers in the middle of them, held in with a snap ring. one washer has splines on the inside diameter, that engage the main shaft splines, the other washer has large teeth on the outside diameter that engage the clutching splines inside the speed gear. that thrust washer is to keep the sliding clutch at the proper depth during gear selection. The speed gears that are back to back of each other on the main shaft have a ground surface on the back sides. these gears are thrust against each other. snap rings on the main shaft keep these gears from sliding up and down the main shaft. the sliding clutches are splined in the inside diameter, and are slid over the splines on the main shaft. when this is assembled, as GW said earlier. the countershaft gears keep the speed gear centered. the main shaft is centered by bearings on the ends. the front one being a spigot bear engaged into the input shaft. the speed gear from front to back are as follows. 4th-5th-3rd-2nd-1st-rev...

my post is from my head and not my books, so there's a chance I left something out. 

[Geoff Weeks]

Joey, that sounds just like Spicer and Fuller, The spacers and lock rings just keep the gear located fore and aft, the countershaft gears keep the gear centered but not riding on the main shaft.

[Joey Mack]

yes sir, but my re-building knowledge of eatons an meritors is weak, with the exception of 10 speed back boxes. However, Mack transmissions where one of my many skills when I worked in the Mack Dealerships.  Thats all i got..

[Mark T]

1 hour ago, Geoff Weeks said:

Joey, that sounds just like Spicer and Fuller, The spacers and lock rings just keep the gear located fore and aft, the countershaft gears keep the gear centered but not riding on the main shaft.

You do realize that based on that theory, tens of thousands of single countershaft transmissions have nothing "centering" mainshaft gears.  Like for instance in an M Drive

[Geoff Weeks]

Single counter-shaft transmission are not built the same way, and this is not a "theory".  Single countershaft have no opposing force so the main shaft carries the side thrust. The gears on those run bushing in the gears that ride on the main shaft

[Freightrain]

My three part video shows how a single CS transmission is assembled.

Bushings are splined onto main shaft, then the gears are bushed and ride on that.

 

 

[Joey Mack]

I enjoy reading your postings.. impressive stuff..