2nd gear Dog Tooth dimensions

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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willik43
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2nd gear Dog Tooth dimensions

Post by willik43 » Wed Jan 11, 2017 6:30 am

Guys,
I would like to know the right, original dimensions, shape of T84 2nd gear Dog Tooth.
DogTooth.jpg
DogTooth.jpg (9.24 KiB) Viewed 285 times
Does somebody have something? I am struggling with quality of nowadays repop parts, esp. here in Europe. Each is a little bit different. Right shape of dog tooth is essential to avoid poping-out of 2nd according my experience of some of my last T84 rebuilds.

Picture of my last purchase.
2ndG.Libor.W.jpg
2ndG.Libor.W.jpg (39.68 KiB) Viewed 285 times
Thank you very much for your inputs.
Last edited by willik43 on Fri Jan 13, 2017 11:19 am, edited 1 time in total.
Petr
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1944 GPW 194969
1945 MB 423482

bazza46
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Re: 2nd gear Dog Tooth dimentions

Post by bazza46 » Thu Jan 12, 2017 12:00 am

Well, for a start, dimensions 'A' and 'B' should be the same. Your picture shows an unevenly worn dog.

It's hard to measure 'C' very accurately, as the vernier tends to slip up the slope, and 'D tends to slip off the tooth.
Also, I presume you are wanting the dimensions, except for 'C', taken at the top of the dog. 'C' as you have drawn it, is at the base of the dog.

The top of the dog will be less as the dog slopes towards the top.

But here are my results, based on second hand but original Willys parts that were working and not slipping off when installed.

There could be a tiny bit of wear for dimension 'D' but not much. Others with brand new parts may differ.

Dimension 'A' and 'B' - 2.17 mm, 'C' - 3.91 mm, 'D' - 2.32 mm.

All measurements taken with my super accurate Harbor Freight $13 (battery included) digital vernier caliper.
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willik43
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Re: 2nd gear Dog Tooth dimentions

Post by willik43 » Thu Jan 12, 2017 3:40 am

Bazza, thank you very much for reply. Firstly my measured 2nd gear is brand new repop gear purchased locally.
My measurements:
A/B: varies in between 2,31 - 2,00 mm
C: 3,50 +/- 0,05 mm bottom of tooth
D: 2,40 - 2,50 mm top of the tooth.
I am not sure if I can use it.
Poping-out of 2nd is a nightmare for T84. I would like to avoid all possible reasons for jumping out. According my experience, worn dog tooth is major cause. In other words not accurate part could be one of those reasons. I am a bit lost :D
Petr
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1945 MB 423482

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Re: 2nd gear Dog Tooth dimentions

Post by Joe Friday » Thu Jan 12, 2017 9:35 am

I'm guessing that A and B should both be 2.0574 mm and C should be 3.968 mm

I can't tell you anything about the width "D" , but If the gear is made correctly, and a .175 cylindrical pin is laid between two teeth 180 degrees apart, the measurement of the outer distance should be OD = 2.306 +/- .001 inches.

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Re: 2nd gear Dog Tooth dimentions

Post by bazza46 » Thu Jan 12, 2017 2:04 pm

Petr, Your gear looks to be within specs regarding the dogs, taking into consideration the difficulty in accurately measuring dimensions.
I've had many years experience in working on the T-84. When I first got my jeep in 1962,after rebuilding the box, it slipped out of second.

Old Mr. Conyard, whom I bought parts from, knew all about that, and he showed me tricks the old timers used to prevent it. This was after checking that the gear and the synchro drum didn't have too much wear on the splines and the dogs. It's not always easily noticeable for the novice, but wear in the first 5mm of the splines of the synchro drum will, coupled with small wear on thedogs of the gear, especially if it's at an angle, will cause jumping out of gear. The thing to look for is a tiny 'step' at the base of the dog, and on the synchro drum, a tiny 'step' a few mm in from the front.
He also said that the bronze bushing in the second gear had to be a snug fit on the shaft - no wobble.

But the main 'fix' he showed me was, outside of the box, to fit the second gear on the main shaft, install the centre of the synchro drum, then the circlip (snap ring) on the front, and check the amount of forward and back movement there was with the gear.
There should have been very little. He didn't use a feeler gauge, but I'd estimate about 0 to .003".
If it was too big ( which it was on mine, he'd cut and file up a washer from tinplate or thin steel, with cut outs inside to match the splines on the shaft. He'd then grind or file it so that when the circlip was fitted in front of the washer, the gear had no fore and aft 'slop'.

Then, when he'd assembled the box, he'd check the brass synchro rings to see if they were too close or too far from their matching cones on the input gear and second gear. He'd just 'eyeball'to see if there was too much clearance, but he said that if when you turned the rear output shaft, the front synchro ring grabbed on the input shaft, it was too close. He said you should just get it so that the synchro rings were riding on the cones, and just a little push with the selector fork on the synchro drum (not all the way to the indent) made them bind on their respective cones, it was right. To adjust, he'd go through his collection of spacers for the rear of the shaft, and select or grind one to fit correctly.

He's learnt this in the Army during or after the war -not sure.
But he never had a gearbox slip out of second, even with second hand gears.
hope this helps
Bazza
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Re: 2nd gear Dog Tooth dimentions

Post by artificer » Thu Jan 12, 2017 3:57 pm

Perfect spot on advice Bazza!
Condenses 100's of G pages....especially 2nd gear float being over .002" needing correction....this is the dog gear wear that is BAD & will always cause jumping 2nd gear


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Re: 2nd gear Dog Tooth dimentions

Post by Ben Dover » Thu Jan 12, 2017 4:24 pm

The wear on the brass Blocking Rings is normally a given as the miles build up, and the second gear excess clearance on the main shaft caused by worn bushings is a valid contributor to slipping out of second during compression braking. It pays to examine the teeth and the fit of a NOS blocking ring on the second gear, those without excess wear will be good candidates for fitting new bushings and will give many more miles of trouble free driving. I have saved a lot of OEM second gears by just installing new bushings.
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