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Unread 02-04-2011, 09:54 PM   #1
RockRodHooligan
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Teraflex Tera low vs. NP231 read here!

So while I've been building up my NP231, I was given 2 Tera 4:1 cases, both of them were trashed(thus free). I decided to pull one of the Tera cases the rest of the way apart to look a little closer as to what happened. Both tera cases had the same failures at the planetary gear set, here is why:

Here is the Tera case ring gear that the planetary gear rides in:

231 case:

Planetary gears: Tera on the left, 231 on right

Tera, 5 pinion:

231, 3 pinion:

The pinion that fell out of the Tera planetary set, and the shaft that is supposed to hold it in place



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Unread 02-04-2011, 10:37 PM   #2
RockRodHooligan
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This is the problem I see with the Tera 4:1, the smaller straight cut gear is all that rides on the ring gear in the case, the larger helical cut gear rides on the inner gear(sun gear?)


But there is nothing on the opposite side of either of those gears to help support large torque loads. The straight cut gear is pushed in by the ring gear, and the helical gear is pushed out by the sun gear(may not be the right name for it, but thats what I'm going to call it until someone corrects me), causing large amounts of stress on the shaft that holds the pinion in place. EVERY ONE of the pinions on the Tera planetary gear had large amounts of play, the shafts probably don't look too much better than the one that fell out, there was so much play, that the pinions barely make contact with the sun gear as it turns.

The 231 planetary set has much wider contact surfaces, the ring gear, pinions, and sun gear, are all the same width, so the ring gear supports full width of the pinion under heavy torque loads from the sun gear, and vice versa. I do not have a detailed pic of the 231 planetary gear, but you can get an idea of it from the pics above, I'll take some more pics of it tomorrow and post them up.
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Unread 02-04-2011, 10:42 PM   #3
03GoldTJ
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Very interesting!
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Unread 02-04-2011, 11:10 PM   #4
lclark2074
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wow alot of damage!!!
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Unread 02-05-2011, 10:34 PM   #5
RockRodHooligan
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NP231 planetary pinion and sun gear:
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Unread 02-05-2011, 11:19 PM   #6
EricsGreen98Tj
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sub. Was thinking of the Terra low option in the distant future, now i dont know.....
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Unread 02-06-2011, 07:06 AM   #7
BillR
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Mark me down as another Jeeper that's NOT impressed with the TeraLow. I had one, and it sounded like a piece of misadjusted farm equipment in low range. The Atlas that replaced it is much quieter and WAY stronger.
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Unread 02-06-2011, 07:11 AM   #8
rob78
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Very interesting post. Thanks for taking the time to do this.
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Unread 02-06-2011, 10:59 AM   #9
pcoplin
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Yes, Tera sucks. Welcome to 2003.
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Unread 02-06-2011, 11:04 AM   #10
Jerry Bransford
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That damage might have been caused by over-revving the planetaries by driving at higher speeds in 4Lo than recommended. Too many drive in 4Lo at higher speeds than is good by shifting into 3rd or even 4th gear which REALLY revs up those planetaries gears, they are screaming at those rpms.
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Unread 02-06-2011, 11:37 AM   #11
BillR
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Quote:
Originally Posted by pcoplin View Post
Yes, Tera sucks. Welcome to 2003.
Agreed!
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Unread 02-06-2011, 11:43 AM   #12
williambmac
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I originally considered the Tera case, but deicided against it after reading alot of not not-so-great reviews.
I ended up getting a good deal on a rubi case and couldn't be happier.
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Unread 02-06-2011, 11:48 AM   #13
EricRollerSkate
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Could be one of the very few aftermarket drivetrain products that I actually think the quality of stock looks way better.
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Unread 02-06-2011, 12:38 PM   #14
Robert J. yates
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Not really vouching for Tera as I had my go around with them years ago but the Tera case in my truck is 10 years old and has never caused me any grief. Now the first case I got from them exploded within 500 miles of installing it and I had a friend with a similar experience but this second case has worked out really well for me. Jerry does make a good point about over-revving the case... it's not built for that style of driving.
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Unread 02-06-2011, 12:47 PM   #15
MO2500
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Interesting info. Thanks for sharing. I too was considering one for my 231 someday but might just save for a while longer and get an atlas later on down the road.
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