Question: T18 Mainshaft, Snap Ring, and 3rd Gear Grooves

[RNDwelding]

Hey fellas, can you help me out? I haven't found answers after having searched the forums here and elsewhere. Images attached.

1. Do I need a snap ring and thrust washer between 2nd gear and the the ‘shoulder’ section (wider ring around mainshaft)? and,
2. Does anyone know why 3rd gear has grooves machined into the outer teeth? I've seen a few gears with one ring, but haven't found any with two rings like mine.

The Novak rebuild kit calls for the snap ring and thrust washer but mentions a conversion and special circumstances (it's unclear to me). However, the Novak and (other diagrams) do not show a mainshaft with the raised 'shoulder' section either. The kit didn’t come with the thrust washer, and these weren't present when disassembled.

There is a groove near the 'shoulder' section that looks like it is for a snap ring, but it’s not as shallow as the other snap ring locations. Maybe it’s an intentional recess? If I don’t put a snap ring there, it looks like I may have an extra. However, I’ve only disassembled the mainshaft.

Relevant info:
Recently purchased 1986 F250 4x4.
T18 (I'm 99.9% certain anyway).
Transmission appears to have been rebuilt before, which makes sense considering it was used as a plow/maintenance truck.
Appears to have the newer style components from what I’ve read.
Case #: 13-01-065-907.
Mainshaft has a larger ‘shoulder’ section than others (I believe that terminology is correct).
Made significant noise in 2nd gear, even more noise in 3rd. The noise was loud enough that you’d have to speak up if talking to someone in the cab. There was no noise in 4th. Owner said the person he bought it from said the gears have always made that noise.
3rd gear has two grooves machined into the outer teeth.
I’m not swapping or upgrading anything, just rebuilding it for the same vehicle.
Novak rebuild kit on hand ending in 4F (which I believe is the correct kit).
The mainshaft I have doesn’t look like the one in the diagrams I’m finding or the one received from Novak (diagrams don't show large shoulder section).
First transmission rebuild.

Better to ask than trial by error! Thanks!
Ryan

P.S. We have a CNC plasma table if anyone needs frame gussets, custom pieces, etc. Happy to help!

[eggman918]

Found these with some good pics ............

http://www.fourwheeler.com/how-to/trans ... n-rebuild/
https://www.ford-trucks.com/articles/t- ... ld-part-1/
http://www.offroaders.com/info/tech-cor ... ebuild.htm

[RNDwelding]

Many thanks, eggman918!

I have been using the first link as a supplement to the Novak instructions.
The second and third links will soon be very handy.

The links don't address my question about the snap ring and thrust washer, though. In the diagram, #12 and #13 are the ones in question. I'm questioning these because my mainshaft doesn't appear the same as the one in the diagram (#15). This is because it has a large raised ring / 'shoulder' section machined onto the shaft. This raised ring section is between 2nd and 3rd gear.

There wasn't a snap ring and thrust washer between 2nd and 3rd gear when I disassembled the mainshaft. Is this because of the large raised ring / 'shoulder' section machined onto the shaft, or was it rebuilt incorrectly last time?

[RNDwelding]

Additional information:

The Novak kit says that #12 and #13 must be purchased separately if a conversion is being done (Ford to Jeep I'm assuming since the shafts are different lengths). Again, it looks like I'll have an extra snap ring if I don't include it, and a thrust washer that would fit this section did not come with the kit.

Given the noisy gears, I'm uncertain if the previous rebuild was correct.

[RNDwelding]

I may have found my answer, but it would be good if an expert can confirm.

I believe my main shaft / output shaft has the thrust machined onto it (image above). This is what I was referring to as the ring/shoulder section. I'm savvy with the terminology like that. Since the thrust is machined onto the shaft, a thrust washer and snap ring are NOT necessary per the links below.

In case this thread is useful to future readers, 2nd gear has a tolerance that should be paid close attention to.

Helpful links:
http://www.earlycj5.com/xf_cj5/index.ph ... aft.83250/
http://forums.off-road.com/jeep-short-w ... shaft.html

[eggman918]

I may have found my answer, but it would be good if an expert can confirm.

I believe my main shaft / output shaft has the thrust machined onto it (image above). This is what I was referring to as the ring/shoulder section. I'm savvy with the terminology like that. Since the thrust is machined onto the shaft, a thrust washer and snap ring are NOT necessary per the links below.

That would make sense and as many applications and as long as the T-18 have been around is quite possible, just test/inspect the clearance between the two ans be sure that there is no interference there. With things that have been around as long as it has you can't assume that it was right when you disassembled,I would do the best research that you can then "follow your gut and logic".........

[mmerlinn]

I know that this is an old thread, but I noticed that no one answered one of the OP's questions, the question about the grooves on the gear teeth.

Those are identification marks. They are the most common type found on gears, although they are only one of many forms of identification used for quickly determining whether a gear is correct for the application. Rather than mis-counting teeth every time, ID marks make it easy to identify the gears.

Some parts cannot be visually sorted without ID marks, most notably some shafts.

My rule is, "An identification mark is ANYTHING that serves NO OTHER USEFUL purpose on the part in question."

Marks can be grooves in the gear teeth like the OP has, grooves BETWEEN gear teeth, grooves in splines, grooves in shafts, ridges in just about any location except for teeth and splines, circumferential grooves on parts, circumferential ridges on parts, casting numbers both raised and recessed, stamped numbers, dots, dashes, and so on.

Hope that clears up the mystery for the OP and for anyone else reading this.