VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 39 transmission

hello all , my 39 master 85 has a pretty good noise when in second gear - only . otherwise shifts great & stays in gear well . options : what other year transmission's will interchange with it ( & where to look for one ) ? or where can a rebuild kit w/ bearings & what ever other parts i need , be gotten from ? i read in the 39 shop manual a 1/2 ton truck would be the same , & it also has hardened gears ( if i read it correctly ) / thanks , frank

I have new gears and shafts, no front or rear bearings for that 39 trans. 1937-39 cars all use the same trans. !/2 tons use a different case and rear shaft.

Frank,
The 1937-39 car transmissions are the same.I would attempt to repair the one you have if it were mine.The front bearing and rear bearing will be very available in new.I would suspect that you will be needing a 2nd speed gear and cluster gear and shaft also.These parts fit 1937-39 only and are not scarce.Bruce should have all the parts that you need.
The cars did not have the hardened gears.

The case (via flame) hardened gears were used on the trucks and are not interchangable with the standard gears used in passanger cars. The case hardened gear is a stronger gear for truck application but has a slightly different involute gear tooth profile and will not mate with a non hardened gear tooth. These gears can be identified by the fact that they have a small hole drilled in the gear and the standard passanger gear does not have this hole. The hole is a 5/32 inch diameter hole drilled in the side of the first and second gear and the countershaft gear also has and extra hole (5/32 dia) drilled in the tube part of the counter shaft assembly,called the hub of the gear. Your shop manual may shows these differences. Sounds like a new second gear and possibly a new counter shaft gear might cure the winning. I have watched these parts on ebay over the last year and they do come up. Just watch out for the 5/32 hole. Good luck.

I believe that I have an NOS transmission cover for the 1939 3 speed. I can send you a picture of it. Cost is $10 + shipping. Good luck on your rebuild.

Is the cover for a floor shift or column shift trans.The column shift cover has the operating shaft built in and would help to improve shifting if old one is worn.This part fits 1939 with column shift only.

Note that in the later years the passenger car gears were discontinued and the hardened gears were used for all applications.This goes for the 1940 and up gears also.
There is no note in the parts book that they can not be "mixed" in one transmission.I often wondered about this.We did it all the time when overhauling these units in the '50's with no problems.

has floor shift - thanks all , for the wealth of information ! please e-mail me with parts list & prices at : frankl7@tds.net .
p.s. i'm still looking for that elusive " ash tray " for project 39 .

The shape of each tooth, the so called tooth profile is slightly different on the truck gears and has a hardnes Rockwell C sale reading (HRC) of 58 where as the gears for passanger cars have HRC of 45. The Thickness of the teeth on the truck gears is .630 inches (on 1st gear) where as the thicness of the passageer car gears on 1st gear is .655 to compensate for the lower strength. The Outside diameter of the gear is 4.275 for truck and 4.290 for passenger car. The root diameter for the truck is 3.520 where as the root diameter for the passenger car is 3.540. These differences also result in a slightly different involute profile of the mating surfaces of the gears and would not allow them to run together normally and could even result in interfernce conditions if severe conditions existed. Similiar differences would be observed for second gear. At best the gears would wear more quickly but run together and could possibly make more noise than normal but still run together. I would not mix those gears on my car. I recently bought a GM chevrolet parts gear for first gear and was shipped the truck gear by mistake (the seller did not know the difference) and returned it for the passanger gear which was shipped to my satisfaction. They were both Original GM Parts. There are also after market gears by Republic Gear. Both are for sale on ebay. Good luck.

It should also be noted that when gears do not have the proper involute profile they can either not run at all (interference) or run together but will not have a constant angular-velocity ratio. This results in a higher pressure angle on the tooth face and can result in increased wear of the softer of the two teeth that mate. But also the constant changing in angular ratio of the gear as it rotates will set up a vibration that could be heard audibly but even worse could increase the alternateing component of stress on the teeth and result in early fatigue failure. I say "could", as the magnituted depends on how severe the differences in dimensions are. I am sorry I cannot translate the given differences above to actual differences in fatgue life. I would just avoid the cituation myself by either running two passenger car gears together or two truck gears together but not mix them for mating. Diffent pairs could theoretically be used in the same transy, but even I would not do that just to keep my car all stock (unless I had no choice).

chevgene & anyone , after 135 miles i drained trans. grease to add lucas oil to try to quiet it some . in the drained grease there ar fine metal " flecks " suspeneded in the oil . i had hoped to drive it this wisconsin season & rebuild the trans. this winter . what are your wise opinions - keep driving or stop & pull the trans. ? hanks for your input . frank

Frank, It will depend on how much driving that you plan to do this summer. For the most part the damage has already been done. If its not making strange noises in high gear and your driving is limited to the southern Wisconsin area I would continue to drive it. Would keep it filled with 140 gear oil and forget the Lucas............on the other hand removing the transmission isn't all that big of a job and you will find the parts a readily available.Rebuilding it isn't all that difficult also.Would recommend replacing the U joint and clutch disc and throw out bearing while the transmission in out.If the clutch is acting OK and the pressure plate looks good I would not replace it as the rebuilts today are not the best.

THANKS CHEVGENE ! i never thought about # 140 . the problem is only in second gear . time is tight for me , right now . can u e-mail me a picture(s) of your 39 ? thx. frank

YES.....If I had your email address. :)

frankl7@tds.net

I was having trouble sending the pictures.They were being returned.I hope some made it.Click on the small pictures to enlarge.

Try W.D. Foster in the Ft. Worth Texas area. I think he had an ad in the last G&D.I purchased all of the gears for my "38" from him (NOS). Mac

thanks machb ! gene i got picts ------------ what a ride you have ? chrome louvre's on the air intake ! what model is this ? frank

Its a Master DeLuxe.The chrome was an accessory for all models early in the year,All the late Master DeLuxe cars had it as standard equipment.