"DIY" hd mcnamara gear

[orangefj45]

i'm working on a 5spd for somebody right now and it's got the usual wear on the main-shaft where the t-case input gear resides. good used shafts are expensive, new shafts are difficult to find and the McNamara gears are'nt cheap either. on top of that we're on a tight budget and timeline so i decided to build my own "full spline" t-case input gear.

for starters, i decided to make a jig to be used to weld the DIY gear. i had an aA440f core sitting on the shelf. the 3rd and 4th gear clutches were wasted, but the output shaft was in amazingly good condition. so i grabbed the trusty dewalt grinder with a cut-off wheel and got busy. a couple of minutes later i had the beginnings of my jig in hand.

 

[orangefj45]

sorry about the crappy pics....

next i figured out how long my jig need to be, chucked the stug shaft up in the lathe and faced it off.

 

[orangefj45]

i had seen a few of the home-made McNamara style gears before and figured i'd take it one step further. instead of welding the input gear/spacer/pto gear together, i'd use another pto gear instead of the spacer and just use the splined hub portion of it to increase the spline length by another 40% ( roughly ). luckily i had a couple extra pto gears on hand so i did'nt have to buy anything.

pic of the stock pto gear.

 

[orangefj45]

don aka fcfab helped me with the gear-chop and welding. his skills are well beyond mine and he offered to help. sure made things easier. i could have gotten it done, but he;s pretty damn tricky.
first we cut the gear up with the plasma cutter, then used a grinder to smooth out the cut surface as much as possible.

 

[orangefj45]

next i chucked the cut gear, now a splined hub, up in the lathe and cleaned it up. this is not essential for balance purposes ( as long as you get the outer diameter fairly consistent ) but it sure looks a lot better.

 

[orangefj45]

now it was time to put everything together to see how it would look. i decided to cut down the middle pto gear so it would be a lot easier to weld all three gears together. without doing so, it would have been next to impossible to get a decent weld on any of the seams.

 

[orangefj45]

everything looked good so it was time to finish the "jig". we used a cut-out from a 1/4" steel plate. don has an ammo can full of "pucks" from drilling holes in plate steel with the hole-saw. they make great spacers and come in very handy when making oddball parts like this. after a little de-burring, drilling a larger hole in the middle and it was ready to be plug-welded to the end of the spud shaft, doing so creates an end-stop for the gears.

 

[orangefj45]

we used one of my snap-on pullers to hold the puck to the stub shaft. we wanted it to be as straight as possible, apply some pressure to ensure good alignment and still have access to plug-weld the hole. worked out really well.

now it was time to slip all the parts in position and snug up the nut at the end of the stub shaft to get proper alignment. so far, so good.

 

[orangefj45]

last but not least, don suggested we'd use duct-tape to mask off the gears. doing so would ensure no welding damage to the tooth and seal surfaces on the gears. sure, the tape would become a sticky mess once the heat of the welding process had it's way with it. but on the other hand, it would protect the essentials and clean-up would'nt be that difficult.

so after 5 minutes of "masking", the setup was ready to be welded. don took care of the honors, then he wrapped the entire assy in a pair of welding gloves followed by a welding blanket. we un-wrapped it an hour later to check it out. still way hot to the touch but looked great. so we wrapped it back up and let it sit. i'll get back to it tomorrow morning to finish the gear and have it ready for install. with any luck, the t-case should be done tomorrow.

 

[Spook50]

You should make and sell these stateside.

Also, check yer PMs!

 

[orangefj45]

You should make and sell these stateside.

no thanks, too much time and effort. but if somebody else wnats to make their own gear, they're welcome to use my little "jig".
however, as a precautionary measure, they'd need tp post a pic of their gear set ready to be welded. i don't want to loan it out just to have to hunt it down weeks or months later.

georg

 

[cullmancruiser]

I did exactly the same thing you are doing except the spacer I used was an old output flange I cut down instead of another PTO gear. I welded everything up real good with 7018 rods on my jig. It did get a little tight on the shaft but a few minutes with a diamond file on the inside of the gear splines and everything fit nicely. I ran it for 3 years until my transmission died with no problems at all
When I tore the transfer down to move it to the NV4500 I'm going to run behind my 4BT, I checked my home made gear out and it was still in perfect shape. Good luck with yours, I hope it works out as well as mine has.

 

[orangefj45]

very cool and good toi know. i assume you had to cut down the spline length from the donor flange?! the pto gear is the same length as the spacer.

got any pics of yours?

 

[Spook50]

Damn, reading this thread is making me want to do this, though with an H55 I hear shaft wear isn't an issue since there's no jarring when you shift into reverse.

 

[orangefj45]

Damn, reading this thread is making me want to do this, though with an H55 I hear shaft wear isn't an issue since there's no jarring when you shift into reverse.

not true at all. shaft wear is an accumulative wear issue on any of the cruiser 19 spline transmissions, h42, h55f and a440f.

 

[Spook50]

not true at all. shaft wear is an accumulative wear issue on any of the cruiser 19 spline transmissions, h42, h55f and a440f.

So do you think it'd be worthwhile to do at some point after putting the new H55 and tcase in, or wait until that tcase is due for a rebuild?

I also meant to ask; why the glove and blanket wrap? Is that to prevent weakening of the steel from rapid cooldown?

 

[cullmancruiser]

very cool and good toi know. i assume you had to cut down the spline length from the donor flange?! the pto gear is the same length as the spacer.

got any pics of yours?

Sorry, no pics. I was new on the forum when I did the job and it didn't cross my mind to do that. I did have to machine the donor flange to the right length but it wasn't difficult. If this thread had started a few weeks ago I could have posted some pics but I'm not taking my case back apart now

 

[FJ60Cam]

...I also meant to ask; why the glove and blanket wrap? Is that to prevent weakening of the steel from rapid cooldown?

Not necessarily "weaker", but rapid cooling will make steel more brittle (harder).

 

[orangefj45]

So do you think it'd be worthwhile to do at some point after putting the new H55 and tcase in, or wait until that tcase is due for a rebuild?

I also meant to ask; why the glove and blanket wrap? Is that to prevent weakening of the steel from rapid cooldown?

that's a loaded question. the splines usually start showing significant wear at 150k miles and more. i guess if you plan on having the cruiser for a looooong time, then it's a good investment to install either a genuine or diy long spline gear setup. if you're gonna drive it rarely or plan on selling in a couple of years, then it might not be a great investment. ultimatley, installing a McNamara gear behind a new h55f trans would be the way to go. decisions, decisions................

 

[orangefj45]

Not necessarily "weaker", but rapid cooling will make steel more brittle (harder).

yup.