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| HP30 vs JBA D30S http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=3&t=73718 |
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| Author: | Honduras [ Mon Jan 14, 2013 1:59 pm ] |
| Post subject: | HP30 vs JBA D30S |
So I've been told that the JBA D30s isn't a very strong diff (I'm currently running 4.88s with RCV CV axles and a set of 33x12.5s pushing in my '02 KJ), and that the HPD30 is much stronger. Obviously I'm not going to be swapping out for an HP30, but the question still stands: What's the difference between the HP30 and the JBA D30S in regards to strength? It's the same size ring, and the D30S housing looks hella strong. It seems that any difference that exists between the two would probably be marginal. Thanks! |
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| Author: | tommudd [ Mon Jan 14, 2013 2:27 pm ] |
| Post subject: | Re: HP30 vs JBA D30S |
Yes the High Pinion is stronger in a way due to where the pinion and gears meet ( up near the top instead of down lower) . Plus more ground clearance under the driveshaft with the HPD . They claim the High pinion are 1/4 or so stronger than low pinion gear sets. The reason like I said are due to the fact while driving forward, the gears mesh on the drive side,up higher and not the low or coast side. So not as much deflection in the gears themselves and flex in the housing itself. Seen both break in similar circumstances though. I'm sure someone will explain even better than I can, but if you don't dog it the JBA should last pretty good I think. Of course any diff can be broken, I've popped a 44 like it was nothing being stupid and seen 60s go boom as well. All depends on how you drive, where you try and go etc |
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| Author: | Honduras [ Mon Jan 14, 2013 3:25 pm ] |
| Post subject: | Re: HP30 vs JBA D30S |
Thanks Tom. I still can't see how the D30S can be considered a weakling, though. The housing is definitely beefy as a mofo. I don't flog on it, but I certainly put it through the paces. Ring and pinion shear, maybe. Then again, that's just my completely uninformed, lack of experience opinion shining through. When you say that you've seen both break, are you saying that you've seen the D30S break, as well? |
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| Author: | tommudd [ Mon Jan 14, 2013 3:46 pm ] |
| Post subject: | Re: HP30 vs JBA D30S |
No sorry meant both of the 30s High and low pinion Only JBA I've had the opportunity to see was when I hung with Marlin and the gang at the Butler Jeep Show Love to have one under mine but............. wife thinks I need to spend money to get her back to the U.S. 
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| Author: | tjkj2002 [ Mon Jan 14, 2013 8:47 pm ] |
| Post subject: | Re: HP30 vs JBA D30S |
You want a high pinion up front and a low pinion in the rear for max strength in the gear mesh. A HP30 is about as strong as a low pinion front D44,a HP44 is about as strong as a low pinion front D60 as far as gear strength is concerned,does not include the axles or anything else. |
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| Author: | Chipppy [ Tue Jan 15, 2013 12:17 pm ] |
| Post subject: | Re: HP30 vs JBA D30S |
Are we talking IFS seem jba is the only option for sale unless you make your own hp30 into an ifs version. Is that a hard task? Does anyone else do that? |
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| Author: | u2slow [ Thu Jan 17, 2013 10:12 pm ] |
| Post subject: | Re: HP30 vs JBA D30S |
Haven't done it, but I'd like to take a stab at it. I have a Ford Dana 50 TTB chunk (yeah, maybe a little big) but made me wonder if the Explorer hp D35 chunk could be modified (it is aluminum, but 27-spline). The other idea I had was to chop up a spare 8.25 and copy the JBA diff. The older ones were 27-spline too. What is often overlooked with the hi-pinion vs. low-pinion argument is when the diff will see the most load. Backing uphill is probably the biggest strain of all for a front diff... and guess what... in this situation the low pinion is working on the drive side of the gears. 
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