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  #1  
Old 04-02-2002, 01:29 PM
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porkchop porkchop is offline
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I had this posted some time ago and not to many people saw it. I figured I would go ahead and post it once again to see if anyone might know. This is the main input gear for a D20. It is the gear that comes off the TH400. I was running this gear with a hybrid D18 (D18 gears in a D20 case). I am thinking of going back to this case since I am pretty sure that all my current problems are coming from the angle that my rear drive shaft is at. Before I do this I need to know why this gear went out in the first place. Nothing happened to the t-case just this gear. Here it is:




Gear Picture

Thanks.


Also if you look at the arrow you will see the crack. Each tooth had this crack on it.

[ April 04, 2002: Message edited by: porkchop ]</p>
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  #2  
Old 04-03-2002, 12:06 AM
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Does anyone have a guess?
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  #3  
Old 04-03-2002, 12:41 AM
tuckers89GW tuckers89GW is offline
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I can't get the pic to show. but i remember if from before.
could the gear not be running true to the other gears? putting too much stress on one edge? Does the crack go all the way thru? I am by no means even close to an expert but logically it seems possible.
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Old 04-03-2002, 12:44 AM
64Trvlr 64Trvlr is offline
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<blockquote>quote:</font><hr>Originally posted by porkchop:
Does anyone have a guess?<hr></blockquote>

It's hard to guess if you can't see it. It won't load for me.
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  #5  
Old 04-03-2002, 12:58 AM
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Well the picture won't work now. It works on my computer at home. Crazy Jeepman hosted it for me. I will have to fix it tonight when I get home. Sorry.
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  #6  
Old 04-03-2002, 01:44 AM
J20fan J20fan is offline
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porkchop,
Once you get the image up I will take a look and scan you the closest match out of my gear and driveline failure analysis manual. I keep here at work and I do not have a scanner at home so it will have to be during the day.
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  #7  
Old 04-04-2002, 01:24 AM
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Lets see if the picture works now.
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  #8  
Old 04-04-2002, 01:38 AM
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Porkchop, I still have to wonder if the gear was large enough in diameter for the D18 gears. While apart did you have a visual check of it meshing from the output hole? I haven't gotten my D20 stuff onto the bench yet but that's what I expect to see unless I get a 29 tooth built to mesh w/ the 18 gears. J20 project
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  #9  
Old 04-04-2002, 01:52 AM
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I made sure everything was meshing good. I had the gears from a D18 that used a 26 tooth main input gear. It is the one that had the 1 1/8 intermediate shaft. So what you are saying is that the intermediate gear was too big and didn't make enough contact on the Main input gear?

[ April 04, 2002: Message edited by: porkchop ]</p>
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Old 04-04-2002, 11:30 AM
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Well no, If the intermediate gear was too big, wouldn't it have bound on the bottom of the teeth on the input gear? What I was wondering is if the input gear were too small in diameter to mesh properly w/ the int gear then it could break the the teeth off easier. J20
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  #11  
Old 04-04-2002, 11:31 AM
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J20fan, any luck on matching the damage up to anything in your book?
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  #12  
Old 04-04-2002, 11:33 AM
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<blockquote>quote:</font><hr>Originally posted by J20 project:
Well no, If the intermediate gear was too big, wouldn't it have bound on the bottom of the teeth on the input gear? What I was wondering is if the input gear were too small in diameter to mesh properly w/ the int gear then it could break the the teeth off easier. J20<hr></blockquote>

I will have to compare them when I get home tonight. I am pretty sure it is the same thickness as the D20 intermediate gear.
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Old 04-04-2002, 01:53 PM
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No PC, I'm asking if the diameter was different causing the teeth to be too shallow when meshed w/ the int gear. Is the diameter of the 26 tooth the same as the 29 tooth? Thickness could be an issue also though. J20
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  #14  
Old 04-04-2002, 02:00 PM
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The D18 that I used for the swap used a 26 tooth main input gear. All the gears I used are suppose to have matched up perfectly. I used the Gear Chart from Novak.

When I compared the gears they all looked the same. I am thinking it might have been a factory defect in the gear or the gear could have had the cracks before and I did not notice them.
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Old 04-05-2002, 02:15 AM
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porkchop, my apologies for not checking yet I have been at home with a killer flu. I have just managed to get my a$$ up. I may be going to work to-day I am not sure yet. If not I will have someone bring the manual home for me. Do you have any other images that you could e-mail to me direct? It would be good to view the root area and the teeth before and after the break for unusual wear patterns.

[ April 05, 2002: Message edited by: J20fan ]</p>
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Old 04-05-2002, 05:22 AM
jeepbob jeepbob is offline
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PC,
It looks like the gear was just plain overloaded. The stress being at the root of the tooth, could mean that there is not enough contact area but I did not see the wear pattern of a tooth not engaged far enough. I do not believe that the D18 is heavy enough to handle a V8 and big tires AND the weight of a FSJ. I have seen these things broken by a stock 227 V6 with 31's when the wheels suddenly got traction in a glass bodied CJ5.
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  #17  
Old 04-06-2002, 02:41 AM
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Yes that may be true with a stock D18 with the 1 1/8 inch intermediate shaft with the three inch diameter bore. The D18 gears in a D20 case are the strongest form of the D18. Also if the gear that broke was from inside the t-case itself I would beleive this more. But the gear that broke was the main gear. This is not part of the t-case so to speak, it is part of the tranny. This gear is used in almost the same way in the D20 and the D18. The only thing about the D20 is that the tcase is run more by the spud shaft than the gear this puts less stress on the gear. Strill it is not as strong as a D20 but it does hold up nicely. Ask Scotty.
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Old 04-08-2002, 02:42 AM
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yeah,so far so good(now knocking on wooden desk [img]tongue.gif[/img] ) ive wheeled it pretty hard and its so far held up for me just fine. i was yanking on a very stuck full size bronco hard enuff in 2wd to squish the axletubes on my rear 44 and its not broken yet. the d18 does use a weaker housing. using a later model 20 housing and buildnig a brace that bolts the pto/overdrive hole and pan bolts will help considerably. the output shafts on the 18,20,and 300 are all conisidered to be a week link,being approximately the same size as the pinion on a dana 44 axle. once youve upgraded to bigger axles and bigger u joints to handle v8 power and lg tires,the output shaft is(in theory at least) the next thing to worry about. however,all d20 failures ive seen have been from simple lack of maintenance,and from popping out of low range due to broken/worn springs under the detent balls. oh yeah-and the one time front axle u bolts allowed the front axle to twist,collapsing the front shaft,and pushing the case right off of the tranny. but that was hardly the d20s fault [img]smile.gif[/img]

i would like to eventually find a d20 pto so i could swap my 18 for a 20. not casue im worried bout breaking the 18,simply cause id really like to have a fwd only back...
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  #19  
Old 04-08-2002, 04:48 AM
J20fan J20fan is offline
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PC, I have sent you 2 e-mails with attachments. These were the closest info I could find and they seem to support jeepbob's theory that it was simply a fatigue failure. If you need a more advanced look into beach marks etc. let me know and I can e-mail you info to assist you in clearly defining the root cause. I cannot publish to my webpage from work so it will have to be e-mail for now. If this is a problem I can post the images this evening.
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Old 04-08-2002, 05:19 AM
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PC, I have recieved a "recipient name not recognized" error on the e-mails I sent. I will try again but this may have to wait until I can post to my page tonight.
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\"UglyGalore\"<br /><a href=\"http://members.shaw.ca/crocker/j20.jpg\" target=\"_blank\">79 J20</a><br />8400# GVW<br />360 T18/D20 Dana 44/60<br /><a href=\"http://members.shaw.ca/crocker/83wag.jpg\" target=\"_blank\">83 Wagoneer</a><br />360 727/208 Dana 44 AMC 20 <br />Impco Propane conversion<br />TFI Upgrade <br />1980 Eagle LTD <br />258 998/119<br /><br />Any fool can makes things bigger, more complex and more violent. It takes a touch of genius and a lot of courage to move in the opposite direction. Albert Einstein
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