79 B7100D gear drive transmission

[Oregon Kiwi]

Hi all,

I have been rebuilding my trans and have an
Issue with the replacement gear it is smaller in height
I have called the supplier and they said my gear is no longer available anywhere and what I recieved is the only one.
Any techs on here tried the new gear?
Either I try and it screws everything up or try source a used one which so far proving impossible.

Btw its gear 17 on the 1st and 4th shaft

 

[torch]

Is that groove for the shifter fork? If so, there could be alignment problems because the groove is further from the gear wheel itself on the replacement so the shifter fork will position the gear incorrectly compared to the original.

I wonder if the replacement is an updated part with a correspondingly different shifter fork or mating gear. You might need to do some research of parts diagrams from different years and see if there were any changes between early and late models.

An alternative is to take the old one to a patient machinist. What I have done in similar circumstances was to turn the original gear teeth off and turn the wheel into a flange. Then mill a new gear wheel with the centre sized to fit the resulting flange and bolted the two parts together:

 

[Oregon Kiwi]

thanks for the reply torch

I found a local gear cutter so hopefully he can remake the gear for not too much. I got a reply from rush gears and they wanted a whopping $4200

Even found some at a salvage yard and still they matched the newer style.


could i possibly have some sort of grey market gearbox??

had a hell of a time getting the correct bearings for the gearbox had to send stuff back after finding differences in bearing sizes definitely not a good idea to just go off the parts diagrams and think they are correct.

 

[torch]

Cool. Good luck with it. Glad to hear you found someone in the business. I imagine it won't be cheap* but it's gotta be way less than $4200!


*I'm just a home hobbyist, and had to make the tool to cut the gear, the arbour to hold the gear, an index plate to position the gear, etc. etc. first. A lot of fiddling to get things right. I probably 12 to 16 hours in that gear pictured above. But my guess is that someone in the business could fix you up in 4 to 6 shop hours.

 

[SidecarFlip]

Cool. Good luck with it. Glad to hear you found someone in the business. I imagine it won't be cheap* but it's gotta be way less than $4200!


*I'm just a home hobbyist, and had to make the tool to cut the gear, the arbour to hold the gear, an index plate to position the gear, etc. etc. first. A lot of fiddling to get things right. I probably 12 to 16 hours in that gear pictured above. But my guess is that someone in the business could fix you up in 4 to 6 shop hours.

Probbably a lot less time that that once the blank has been turned to size. A gear hobbing machine can crank out gears pretty quick. I do mine like you do but on a Bridgeport with an index head. Takes a lot of time and don't forget the gear needs to be heat treated after machining.

Kind of surprised Kubota don't have the part. I get parts for my M's and they are 10 years old, no issue other than they have to come from Japan so wait a while.

 

[torch]

Probbably a lot less time that that once the blank has been turned to size. A gear hobbing machine can crank out gears pretty quick. I do mine like you do but on a Bridgeport with an index head. Takes a lot of time and don't forget the gear needs to be heat treated after machining.

Kind of surprised Kubota don't have the part. I get parts for my M's and they are 10 years old, no issue other than they have to come from Japan so wait a while.

Yeah, but his B7100 is almost 40 years old!

I don't have a Bridgeport, much as I would love one. I have a 3-in-1 tucked in the corner of the garage. It works, but takes time to switch between turning and milling setups.

I don't have an indexer, per se. I used a rotary table mounted to the table vertically, with indexing plates. In the case of the above gear project, I didn't have a plate with the right number of holes so one of the things that took time was to make an index plate:

Presumably an established shop will already have this stuff, or, like you say, an actual gear hobbing machine.

As for heat treating, I think I would opt for case hardening in this application.

 

[Lil Foot]

Nice work, especially considering the three -in-one. Be interesting to see what you cold accomplish with "real" equipment. Goes to show that you can do some amazing work on less than ideal equipment with patience & care. Well done.

This thread worries me a little, as I have a 1979 B7100 gear transmission myself.

 

[Oregon Kiwi]

Yeah, but his B7100 is almost 40 years old!

I don't have a Bridgeport, much as I would love one. I have a 3-in-1 tucked in the corner of the garage. It works, but takes time to switch between turning and milling setups.

I don't have an indexer, per se. I used a rotary table mounted to the table vertically, with indexing plates. In the case of the above gear project, I didn't have a plate with the right number of holes so one of the things that took time was to make an index plate:

Presumably an established shop will already have this stuff, or, like you say, an actual gear hobbing machine.

As for heat treating, I think I would opt for case hardening in this application.

wow wish i had the equipment/know how.

The machinist "old guy in his late 70s" said it would take several of his machines and would have to send it out to be heat treated which would be $100 or so. whats the difference with "case hardening"

hopefully i get a promising call next week and he has a reasonable price for the job.

lil foot
no need to be worried i believe the reason my gear tooth broke is because the pto Bearing was destroyed and i suspect a ball bearing got caught up.

plus i`m already doing the trial and error for you
i am by no means a tractor mechanic.

 

[torch]

Case hardening is just one of many forma of "heat treatment".

The term "heat treatment" is a bit of a catch-all for many different applications. Steel can be hardened by heat treatment and it can be softened by heat treatment. The alloy, temperatures, times and cooling all affect what happens.

For example, O1 tool steel alloy can be hardened by heating it to a dull red glow (until it becomes non-magnetic) and then plunged into room temperature oil. If you were to plunge it into water or brine (which cools faster than oil) it could shatter, but even cooled in oil it will be somewhat brittle, and needs tempering. To "draw it back" (ie: temper the steel) one then heats it to a lower temperature (straw coloured) and allows it to cool slowly. To remove all hardening ("annealling") one heats it up almost to the melting point and cools it slowly.

As a general rule of thumb, the harder you make a steel, the more brittle it becomes and vise-versa. The trick is to strike the right balance of toughness and hardness.

Case hardening hardens just a surface layer instead of through the entire piece. Usually used on low-carbon steel like 1018, the piece is heated red-hot and coated with a film of high-carbon material (eg: "Kasenit") and held or re-heated long enough to drive some of the carbon into the outer layer of the steel. Then a final quench in oil or water to harden that layer.

The result is a hard wear surface over a tough inner core. The thickness of that layer is limited to a few hundredths of an inch though. Good for gears, not good for something that will be ground down, as with, say, sharpening.

 

[North Idaho Wolfman]

could i possibly have some sort of grey market gearbox??

Give me the serial number in its entirety:
It will be stamped on the side of the clutch housing (tunnel) and be something like B7001-XXXXX.

The new gear that you have is 66704-14460 right?

I'm betting that if you changed the spur gear (15) that's behind it, that gear would work for you.

 

[Oregon Kiwi]

Thank you torch for the explanation much appreciated.

North Idaho wolfman
B7001-46211is on the clutch housing.
The transmission had terrible abouts of rtv sealant so it definitely has been worked on in its life.

Yes it was 66704-14460. I later discovered it did not even fit on the shaft and have since returned it.
I believe I need (66611-14460) but it has been discontinued and unobtainable.

 

[North Idaho Wolfman]

By serial # it should have taken the newer gear set, but like you said someone has gotten in it so all bets are off:

Here is the gear your looking for, but your probably not going to like the price:

https://conag-aftermarket-oem-parts...ooth-transmission-gear-fits-b7100-b6000-b7001

 

[torch]

Good find!

I don't think a machinist could make/repair the old one for less than that price.

 

[SidecarFlip]

RTV and UDT don't make good bedfellows. You need to be using 3 bond or anerobic sealant, not RTV.