Winner Borg Warner T-5 tranmission in 1/3 scale

[gbritnell]

As a follow up to the thread I started on my 302 V-8 engine I am posting this abbreviated thread on the building of the T-5 transmission to go with it. Each fall I somewhat plan out what my projects will be for the forthcoming winter season. Having just competed 5 hit and miss engines for someone else I was ready for a change. My sons have always been into cars and while visiting one day I noticed a T-5 transmission laying in the corner. This transmission happened to have come out of a Mustang but similar units are used in many other automobile brands but with different ratios and tailshaft extension. I thought this would be a good project and eventually I could bolt it up to my engine.
I lugged the trans home and went online to see how they came apart. There was a very comprehensive maintenance manual online which helped tremendously. I proceeded to dismantle the transmission and make dimensioned sketches of all the parts. These sketches were later turned into Autocad drawings.
One of the issues that needed to be addressed was the type of gears in the box. Most all modern day transmissions have helical gears in them mainly because they run smoother which equates to quieter operation. A fellow on another forum had come up with a way to make helicals in the home shop but that would have required making tapered sleeves for each each gear to get the right helix. I really didn't want to go to that extreme so I settled on spur gears. Even at that I had to solve some problems. As the trans would be a direct 1/3 copy I wanted to keep the scale dimensions as close as possible. With the main shaft to countershaft spacing set I started figuring out how I could make the gears that would fit that center to center dimension and still have progressively varying ratios. I ended up making 3 hobs of different pitches to cut the gears, 36, 40 and 48. Although visibly looking at the gears inside the case they look the same there are the 3 different pitches.
This type of transmission is commonly referred to as a constant mesh transmission. That means that all the gears are turning while the mainshaft is rotating. To select the proper gear a splined bushing is moved between gears and the splines engage with equally splined gears. There is of course synchronizers but I simplified these.
The main cases are made from 6061 aluminum. The gears are made from 12L14 steel. The shafts are W-1 drill rod and various bits are steel and bronze. The shafts ride on ball bearings at each end.
I started with a block of aluminum, layed it out, machined all the shaft and bolt holes and then started whittling away on the inside first and then the outside.
gbritnell

 

[gbritnell]

The block of aluminum was roughly layed out with locations of bosses and ribs. The metal was then slowly cut away trying not to remove anything that was supposed to stay. All of the machining was done by hand with the aid of digitals on my mill. Step-off charts were generated in Cad to cut radial contours and tangent points between features. The inside was cut first as it would have been near impossible to chuck the part starting from the outside. The next step was to do both outer sides leaving the bottom square, again for chucking purposes. Once the sides were completely machined the bottom was cut using the same techniques.
gbritnell

- - - Updated - - -

With all the machining completed the case was hand finished using first, small carbide burrs in a Dremel tool with a flex shaft. This was followed with small mounted stones, files and riffler files and finally with small sanding sticks of various grits.

- - - Updated - - -

 

[gbritnell]

The next piece to be machined was the tailshaft housing. This was approached in the same manner as the main case. Starting with a block of aluminum layout lines were added and shaft and bolt holes were done first. This was followed by all of the internal machining.
gbritnell

- - - Updated - - -

As with the main case I left stock on the bottom of the tailshaft housing to facilitate setups for machining. With so many irregular surfaces on these parts you have to think far enough ahead as to how you will hold the part for machining. The second picture shows how I stepped of one of radii forming the outer shape. As and apprentice patternmaker we learned how to sine and cosine radii on a mill. This was long before CNC.
gbritnell

 

[gbritnell]

These next photos show the tailshaft housing in various stages of machining and finishing.
gbritnell

- - - Updated - - -

The last 2 housing pieces made from aluminum are the top cover and the input shaft housing. The top cover needed some very accurate machining as the shift shaft and shift levers had to be properly located to function.
As with the previous parts a lot of stepping off was required to get down to the finished shape.
gbritnell

 

[gbritnell]

With all the housings and outer covers finished it was time to start on the inside pieces. The first one is a shifting lever that operates the reverse gear set and the overdrive set. I machined this from 1018 CRS. I made up a fixture plate to bolt the stock to and then started the machining. This part has 2 slots in it that move the gear sets. It is pivoted on a shouldered screw in the side of the case. As it rocks backward or forward it moves the shifting yoke through a small roller wheel. I drilled out the corners and the spots where the straight slot changed angles. The remaining stock was filed out to produce the shape that you see.
gbritnell

- - - Updated - - -

This is jumping ahead a little but you can see the lever mounted onto the inside of the case and moved from one position to the other.
gbritnell

 

[gbritnell]

The next phase was to cut all the gears. As I mentioned at the beginning I had to make up my own hobs partly because of the bastard pitch diameters and also what if would have cost to buy involute cutters. I have a small dividing head that has become invaluable for just this kind of work. The first gears were the multiple gears machined onto the countershaft. The third and input gears are close together and there was no way to machine the third gear cog without running into the input cog so the solution was to make the countershaft in 2 pieces. When they were finished the 2 parts were pressed together and pinned.
gbritnell

- - - Updated - - -

Here are pictures of the 2 gear sets, after machining and after assembly.
gbritnell

 

[gbritnell]

The following 2 photos show all the gears inside the main case. The last 2 show the overdrive gearset which is located in the tailshaft housing. You can see the splines that the gears are located on and the shifting collars that join the 2 sets of splines per gearset.
gbritnell

- - - Updated - - -

 

[gbritnell]

The final 4 picture show the finished transmission including the replica Hurst shifter with shift stops and all.
gbritnell

- - - Updated - - -

Here is a video link to the transmission in operation. http://youtu.be/dcLtBLC5yqo
gbritnell

 

[Charley Davidson]

Absolutely amazing

 

[mtnlvr]

That is amazing. You are truly talented. Who many hours would you estimate it took?