Twisted mainshaft overdrive

[SwedishSunbeamfreak]

hello! I just got a complete od set from an Alpine 5. Speedo, cable, switch, gearbox and od, propshaft. It was from a Wreck that been sitting for 40 years. So i thought i’d strip gearbox and od to molecules and clean and change bearings etc. but now you sceard the poop out of me. Is the mainshaft scrap? Its a little twisted? I is not of or anything but a little twisted. I understand that if the mainshaft twists of completly the car will stopp but why wound it not work with a little twist? I now i have to drive gentle when i engage and disengage the od but otherwise it should work? (No burnouts ofcorse)

Sorry for bad english i’m from sweden.

 

[Bill Blue]

Twisted shafts will cause the overdrive to fail, but rarely cause the car to stop.

Bill

 

[SwedishSunbeamfreak]

Twisted shafts will cause the overdrive to fail, but rarely cause the car to stop.

Bill

But why will it fail? What will happen, ist like 2-3 millimeters? There is no sensors that can read wrong?

 

[puff4]

I wonder if there's some value in having a small run of these shafts reproduced in a more tough material. I'd imagine you'd get quite a few folks wanting to add overdrive, and many more who would want to replace the original shafts in their OD boxes. Mine is still OK, I believe, but I'd want to replace it for the sake of durability.

 

[SwedishSunbeamfreak]

I wonder if there's some value in having a small run of these shafts reproduced in a more tough material. I'd imagine you'd get quite a few folks wanting to add overdrive and many who would want to replace the original shafts in their OD boxes. Mine is still OK, I believe, but I'd want to replace it for the sake of durability.

Yes of corse but why wold the od fail because of a little twist??

 

[Bill Blue]

My understanding is that when the OD shifts, there is a sliding motion along the shaft. When the twist becomes large enough to prevent the sliding motion, the O.D. fails to shift. That was the explanation given by Tiger Tom during a flashlight teardown of an Alpine tranny in 2003.

Bill

 

[SwedishSunbeamfreak]

Ahaaaa i understand!

 

[puff4]

Meanwhile, if you've got an OD, I'd suggest doing as I have always done... go into OD with a very light throttle, and always use the clutch when disengaging. Saves considerable wear and tear on all the OD bits.

 

[Jimjordan2]

I agree with this suggestion. While you certainly do not "have" to clutch for O/D, it feels so much nicer than having it (slightly) Slam into gear. It just "feels" hard on the gearing. Think of just shifting for a 5th gear.

 

[Bill Blue]

Unfortunately, all this is true. But it takes a fun setup and turns it into an Old Fogey Mobile. Someone needs to adapt the old Volvo trans to the Rootes engine. My son bought a clapped out Volvo with the six cylinder engine, four speed with OD. With about 250,000 miles on the clock, it all worked beautifully. The design is good, the Rootes adaptation STINKS.

Bill

 

[SwedishSunbeamfreak]

Yes the volvo m40 is really badass. I had an volvo duett and i gave all i could and it always did what it should. But volvo is stronger engines and gearboxes. It is hard to kill a b18-b20. The cluch is much bigger on volvos, the alpine clutch is like a baby clutch haha

But i think why not send the shaft to be warmd, retwisted and then really harden?

 

[Bill Blue]

Because if you really harden it, it becomes brittle and will break in a heartbeat. But you have the right idea. There is a sweet spot in which carbon steel is very resistant to bending, yet is not brittle. Very tough, like a spring or a high quality bolt. Unfortunately, I have just told you everything that I know about the subject of heat treating steel.

Bill

 

[SwedishSunbeamfreak]

Yeah...

I just tink the shaft is not right harden. I mean normal outputshaft on gearbox without od do not twist. Even if it is a little bigger. It is quite a small car and small engine. The hardest part is to do the splines otherwise a good shop can create same shaft esay.

 

[Bill Blue]

Normal output shafts are not subjected to the stress of these O.D. output shafts. The shift is hard and quick. I think the damage occurs when shifting from O.D. to direct drive, especially with the throttle closed and in third gear. There is quite a jolt. I am pretty sure that is how I destroyed the O.D. on my Series II. I remember my last O.D. downshift. I was humming along at 65-70 in west Texas and decided to get off the highway for the night. Let off the throttle, downshifted into straight 4th and continued into town for the night. That was the last time the overdrive worked. I had no idea at the time what the problem might be. Nobody did. This was in 1966 and the overdrive units were largely a mystery, other than they were supposed to be designed so they could not be destroyed. In fact, when I took possession of the car in 1963 (purchased new), I was told I could shift it anyway at anytime I wanted, I could not hurt it. It lasted about 30,000 miles. But it sure was a blast while it lasted.

Bill

 

[alpine_64]

Iirc the later all sync gearbox D-type shaft is more susceptible to twisting as it was thinner than the early non sync 1st shaft.

Not sure aboit J type hunter box but they J type od is known to be more robust... Not sure about the mainshaft

 

[SwedishSunbeamfreak]

Normal output shafts are not subjected to the stress of these O.D. output shafts. The shift is hard and quick. I think the damage occurs when shifting from O.D. to direct drive, especially with the throttle closed and in third gear. There is quite a jolt. I am pretty sure that is how I destroyed the O.D. on my Series II. I remember my last O.D. downshift. I was humming along at 65-70 in west Texas and decided to get off the highway for the night. Let off the throttle, downshifted into straight 4th and continued into town for the night. That was the last time the overdrive worked. I had no idea at the time what the problem might be. Nobody did. This was in 1966 and the overdrive units were largely a mystery, other than they were supposed to be designed so they could not be destroyed. In fact, when I took possession of the car in 1963 (purchased new), I was told I could shift it anyway at anytime I wanted, I could not hurt it. It lasted about 30,000 miles. But it sure was a blast while it lasted.

Bill

I thought od cars did not exist in US?

 

[Bill Blue]

I thought od cars did not exist in US?

Not sure how to take this. Do you mean Alpines with od or od in general? O.D. was supplied on about a third of the Alpines. So they were not common, but rare, either. Overdrive came on the American car scene in the 1930's, being installed on all makes and models as an option. They were installed on almost all Studebakers. But the American overdrive design was nothing like the Laycock design.

Bill

 

[SwedishSunbeamfreak]

Not sure how to take this. Do you mean Alpines with od or od in general? O.D. was supplied on about a third of the Alpines. So they were not common, but rare, either. Overdrive came on the American car scene in the 1930's, being installed on all makes and models as an option. They were installed on almost all Studebakers. But the American overdrive design was nothing like the Laycock design.

Bill

I mean on the alpines, heared that americans didnt want Thought it was so the car not would go to fast? What is an american overdrive like?

 

[Bill Blue]

I mean on the alpines, heared that americans didnt want Thought it was so the car not would go to fast? What is an american overdrive like?

Not go too fast? Not in the land where speed is king. Overdrive was usually seen as a way to improve gas mileage. Not very important when gasoline is $.30/gal and overdrive costs $100 or more.
The American version allowed free wheeling while coasting in overdrive. Engagement/disengagement was entirely controlled by speed and gas pedal. At speeds above 30 mph (and in second or third gear), the unit would engage whenever the car was coasting. It would revert to direct when the speed dropped below 30 mph or the gas pedal was at maximum (passing gear). After passing, the od would engage when the driver let up the gas pedal. There was a cable control that allowed the driver to lock the unit into direct drive. The free wheeling was a safety concern, this was in pre disc brake cars and it was easy to overheat the brakes.

Bill

 

[Barry]

A strange coincidence is that the remnants of Laycock de Normanville exist as Gear Vendors (https://www.gearvendors.com/index.html) which makes virtually indestructible O.D. units for the high HP (up to 2,000) performance car market.