Side shaft gears?

[Dave G]

I happen to have an automatic transmission rebuild going on this week. This is for a car I'm putting together this spring to go racing. The output shaft has a helical gear hobbed onto it for the speedometer drive gear to mesh with. I counted the number of teeth on the gear and came up with 13. I used to do more transmission rebuilds 20 years ago than I do now so I have collected spare parts for the trans that I use. I looked in my box and found a 26 tooth speedometer gear. So I was wondering if I could salvage a bad output shaft and chop saw the gear portion away and then clean it up on the lathe. I'm going to see a friend of mine that does alot of transmissions to see if he has any bad shafts laying around and if not, then save me one when he does find one. The shaft is probably made from 1053 steel and is hardened so I don't know how successful I will be. I'll just have to try. The driven gear is plastic so I question if it will be strong enough to drive a model sideshaft. I figured I'd post this to see what you guys think. Will this be a good source of sideshaft gears? Dave

 

[Ken I]

You will often find much the same sort of gear take off from a camshaft to the oil pump / distributor drive.

All in steel and may be easier to come by.

Just a suggestion.

Ken

 

[Lakc]

Thats an output shaft from a 727 torqueflite, the red gear was a 33 tooth I seem to recall, but the number of teeth is embossed on the side of the gear itself, almost visible in the pic. The bent tab locking bolts on the governor housing stopped sometime in the mid 70's, so I am guessing the shaft is older then 1978 or so.
Skew gears are a fairly common way of transmitting power at right angles.

 

[hitnmiss49]

Dave,
I would worry about that plastic gear. I have used the crankshaft gear and distributor pinion gear from a VW engine. The crankshaft gear is brass and the pinion is hardened steel. I heat the pinion shaft cherry red and put it in a bucket of sand to cool slowly. Once softened it machines quite easily. The only drawback to these is the crankshaft gear is pretty large and it needs a bushing made to fit the crankshaft for a model engine.
The engine pictured with my ID has these gears. It has been run at shows for several years without any problems.
Lonnie

 

[Lakc]

The plastic gear is not good for much more torque then a long speedometer cable. I cut one of those shafts once, its hardened very deep, about halfway through, and there are no real "soft" areas inside to mount the gear with once you salvage it.

 

[Dave G]

Very close Lakc, It's a 904 from 1973, and a 26 tooth gear. Good eye. I was in the proccess of the rebuild and just thought I'd bring it up to you guys. I was thinking the same thing about the plastic gear. I just always try to find things that don't need finding, another mental flaw I guess. It would probably be more work than it is worth to modify and I'm glad someone has already tried it so I can save myself alot of work. Thanks guys, Dave

 

[Lakc]

In the later overdrive versions that became the intermediate shaft, and I had to cut one up to use for an alignment tool. Cross section shows the hardening depth pretty good. If I run across it I will shoot you a pic. Glad it wasnt my bandsaw blade I ruined on that. I was not yet very versed in the ways of metalworking back then. Maybe I will see you at Norwalk if summer ever comes.... :'(

 

[Dave G]

Well Lakc, you figured out my hangout spot. Looking forward to good weather and the smell of burning rubber too. Look for a light blue 65 Dart or a white 67 Dart( my son's) or a middle age guy that is having too much fun.
In one of my old jobs, I had to check case depth of case hardened parts. We would cut the parts by abrasive saw and then dip them in sulfuric acid and then the difference in colors could be used to check for case depth. I was an apprentice at the time and they used to assign us to the metalurgy department for 3 months. An experience I'll never forget. I figured I"d cut a shaft and then etch it to find the case depth before trying to bore it but it sounds like it is made from a through hardened steel. Probably 1053 or 1070 steel. Not much fun to work with in it's hardened state. I never liked those hard turning jobs anyways. Thanks for the headsup, I like to be successful in all my endeavors so I think I'll finish my trans rebuild and then move on. Dave