A bolt in M40 gearbox with no torque tube modification. My friend Nöru and I were discussing the Volvo M40 gearbox and the threads on here, about it, and the difficulty of getting the gearbox to fit into a Model A without changes to the torque tube. Me being a sucker for punishment, said I would have a go at it. Now here in Europe Volvo gearboxes are not hard to find and nor expensive. There is a lot of info on here, the H.A.M.B. about what you have to do, and I studied these threads, and my friend dropped a Volvo gearbox off to me to have a play. Here’s a short summary of what’s needed Model AA truck bellhousing, or aftermarket short bellhousing Volvo M40 gearbox modify flywheel for Volvo clutch Adaptor for Volvo input shaft pilot bearing Adaptor model A clutch fork to Volvo throw out bearing Shorten Volvo input shaft about 16mm Adaptor centring ring Volvo gearbox to Bellhousing Volvo M40 next to Model A gearbox
I pulled to gearbox apart to get the output on to the bench This shows the rear bearing support and first gear with synchro Output shaft fully dismantled
The output shaft is just too long. After thinking about a few different ways of making this work, modifying the splines on the uni joint etc. The shaft is very hard, even with carbide tooling and a high speed head on my mill, cutting splines to match the Ford uni wasn’t going to be fun The area in the photo shown as splines and speedo drive is undersize for the Ford uni joint max diameter So I got the out Tig out, and carefully, trying to minimise distortion, welded them up Setting up to check the welded shaft for straightness
There was a bit of a bend in the shaft, but in the thread area, using a four jaw chuck to compensate for that, I machined the shaft to dimension Set the shaft in the mill, and cut the splines to match the Ford uni, this went easier, as the welding had taken a bit of the hardness out of the shaft, I don’t think this will be an issue, but only time will tell
I machined the splines all the way along the shaft, under the bearing area and up to where a spacer/thrust ring goes before the first gear surface Uni test fitted on shaft
So here’s my dastardly plan Had to get the colouring pencils out for this one, doing this on an iPad, don’t have any fancy software, it may look like something Wile E Coyote could come up with Adaptor gearbox side, copied dimensions from Volvo but bearing depth adjusted for the narrower bearing, holes drilled for the back of the Volvo gearbox, and a relief hole for the reverse gear shaft. Please excuse the machining marks, trying to do too many things at once
Shortening the shaft and hole drilled and tapped to accept the original bolt Machining the uni down to go under the bearing
Details on the adapter, allen head bolts to mount to the gearbox recessed in to clear the uni, holes for the shift rods to come back into the adapter. Holes for the TT clam shell mount up, here I stuffed up, the top hole interferes with the shift rods, I should of rotated the TT clam shell to clear or possibly used a V8 style clam shell, they only have 4 mounting bolts. Another thing I used a V8 uni joint, they are stronger than the original Model A style. I used steel for the rear adapter for strength reasons and I could get good quality steel in that diameter (165mm). Not shown in these photos, but I drilled and tapped a hole for a zirk fitting to grease the uni
Assembled, it’s a bit tricky to get it together with putting the lay shaft in and the shift shafts, then the rear adapter bearing carrier
Side by side, a bit of optical illusion with the camera, with the ruler on top, it’s not sloping down, they are the same length. A bracket for the pedal shaft has to be made, and another to mount the handbrake lever
Dimensions for the rear adapter, I made this with a lot of machine a bit, test fit, machine a bit more, so there’s not a lot of exact measurements, I would test fit for clearance, assemble to see how it went. While I was doing this project, I had a skiing accident and ended up getting my hip replaced, which slowed things down, so it won’t be fitted to the car until winter, there’s too many events on now to take the car off the road. It will be going behind a rebuilt G28, so we will see how it holds up. Typical when this was under development, I got sent this I guess great minds think alike
About once a month I am totally amazed at talent, skill, and ingenuity some folks exhibit on this forum. This is one of those times.
Thank you for the replies, I put a lot of photos, to show as much as possible, and I’m not the best writer. Even though I have been on the spanner’s for more than 35 years, I have learnt so much from the H.A.M.B, and keep learning everyday. The dimensions and drawings are my way of saying thanks
Not only can you make the plan, you can bring it to completion with your matching machining skills! Great work!
The Jalopy Journal
