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Unread 04-30-2013, 02:10 PM   #31
Stormpaw
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Oh, I forgot... the AX15 is a stronger transmission than the AX5 or SR4 (I am guessing that is what you currently have), and compatible with the AMC I6 with just a little work, and the Dana 300 with an adapter.

However, getting smaller axle gears would achieve pretty much the same result (other than the stronger transmission case.)

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Unread 04-30-2013, 02:16 PM   #32
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Quote:
Originally Posted by frhrwa View Post
why aren't you considering the T15? "supposed" to be a better trans for the 6 cylinder ?
sorry, I meant the AX15
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Unread 04-30-2013, 02:34 PM   #33
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Quote:
Originally Posted by frhrwa View Post
sorry, I meant the AX15
Bah, I just realized I did the same thing.

(Fixed previous post.)
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Unread 04-30-2013, 08:14 PM   #34
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Thanks for all the info! Just to clear things up I'm not just looking for better mpg but the main thing is to lower my Rs so I don't tear my engine up. I just got these gears in so I'm not regearing. I go rock crawling a lot but I go on the highway a lot too. What would be the best transmission for lowering my Rs? I'm going to tune everything and get some headers.
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Unread 04-30-2013, 08:44 PM   #35
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Well, in that case you were on the right track, an overdrive would be the way to go. The AX15 and NV4500 are the best I can think of (someone else probably knows more) if you want a manual transmission. Both would give you an overdrive fifth gear. The AX15 would raise your low end slightly (still assuming you have an SR4), and the NV4500 would lower it considerably. I have no idea how much a swap for either would cost, but I am pretty sure the NV4500 are quite a bit more expensive.
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Unread 04-30-2013, 09:12 PM   #36
DropeTine99
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The AX15 would bolt in wouldnt it?
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Unread 04-30-2013, 09:29 PM   #37
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Quote:
Originally Posted by DropeTine99
The AX15 would bolt in wouldnt it?
You need a conversion pilot bushing, a clocking ring for the t case, modify the drive shafts and convert to a hydraulic clutch. But yes, the bell housing will bolt up to a 4.2L
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Unread 04-30-2013, 09:35 PM   #38
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Apparently, the front bearing retainer has to be changed on the earlier models to fit the 258, but the later ones should bolt right up. You would, however, need an adapter to mount the Dana300 to the AX15.

I hope that helps.
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Unread 04-30-2013, 09:37 PM   #39
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Quote:
Originally Posted by DropeTine99 View Post
My tach stopped working but I top out somewhere around 60 mph, I'm guessing 2900-2800 rpms lol I went from a 2.73 R&P to the 4.10s and lost like 10 mph and some mpg. I don't get it lol Only thing I could think of was the tranny.
If you're truly doing 60mph and have tires that are actually 33" (most aren't) you should be turning around 2500 rpms at 60mph with the four speed (1:1 ratio in fourth).
Plug your info into this calculator.
www.grimmjeeper.com/gears.html
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Unread 04-30-2013, 10:04 PM   #40
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None if my gauges are working -_- how much of a difference would just getting headers, electronic ignition and get a better carb make? Think it'd lower my Rs by at least 200? And I can't use that calculator without my speedometer working can I? Ill start looking for a AX15!
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Unread 04-30-2013, 10:41 PM   #41
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Quote:
Originally Posted by DropeTine99 View Post
None if my gauges are working -_- how much of a difference would just getting headers, electronic ignition and get a better carb make? Think it'd lower my Rs by at least 200? And I can't use that calculator without my speedometer working can I? Ill start looking for a AX15!
Any engine tuning or mods IE: headers, will not change how fast the engine turns at a given speed. That is purely mechanical dependent on final drive ratio, tire size and transmission output ratio. All three of those upgrades will get your engine RPM's up faster and depending on other factors raise your top RPM.

If you really plan to seriously rock crawl, an AX15 is probably not the best choice either. The NV4500 is the best choice for strength with an O/D
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Unread 05-01-2013, 12:02 PM   #42
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Oh, that is a nice one CSP.

Quote:
Originally Posted by DropeTine99 View Post
And I can't use that calculator without my speedometer working can I?
Yes, you can. It is similar to the Novak gearing calculator I mentioned earlier. Just enter your transmission, t-case, axle gears, and tire size and it will tell your RPM at a given speed, speed at a given RPM and crawl speed at a given RPM. Although, that last one seems to be off (probably just needs to be divided by 100.) It also lets you compare your current set up side-by-side with the setup you are considering.

With a manual transmission, speed at a given RPM will always be the same for a given set of gears and tires unless:
1. Your clutch is slipping.
2. You wheels are slipping.
3. Your drive train is tearing itself apart.

However, getting your gauges working might be a good first step whatever you decide to do so you have real data on the performance of your engine to work from.
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Unread 05-01-2013, 07:45 PM   #43
DropeTine99
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Ill start looking for the transmission. Thanks fit clearing things up! What's the underdrive?
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Unread 05-01-2013, 09:07 PM   #44
Stormpaw
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Underdrives are an extra set of reduction gears that can be installed between the transmission and t-case (sort of like having a second t-case to drop into low.) An interesting device, but expensive and not very practical in short wheel base Jeeps.

If you are asking because of the calculator, just leave it on none.
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Unread 05-01-2013, 09:28 PM   #45
DropeTine99
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Thank you! Lol
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