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6 speed manual swap....can do???

Jeepthing88

NAXJA Forum User
Location
Gurnee
ok i've wanted to drop in a manual into my XJ for awhile now and I've found a few at the junkyard that have the AX-15 that will mate up with my 4.0 and my NP242 Transfer Case. Upon further thinking...I thought that if I'm gonna go through all the trouble of swapping in a manual, I'd really like to throw in a 6 speed. has anyone done this? is it even possible? from what research I've done the 6 speed in the newer jeeps is the NSG 370. Thanks for your help!!!
 
i m not sure about this but
check 6 spd out of a toyota supra, i bet it can handel a lot, not sure about mating it to the transfer case
i heared that they used AW4 as their auto.
 
There's no advantage to installing a 6-speed tranny in a 4.0 XJ. The engine has such a flat torque curve that 5 speeds are more than enough. Go for the AX15. It's much cheaper than the NSG370 and it'll do the job better.
 
And the AX-15 will be easier to find.

Just make sure you've got the right input spline count for your transfer case - later AW4s (1990 and up, I'm thinking...) used the later 23-spline output shaft, same as the AX-15. Earlier AW4s used the 21-spline (same as the Peugeot,) and you'll have to grab the transfer case along with the transmission.
 
Dr. Dyno said:
There's no advantage to installing a 6-speed tranny in a 4.0 XJ. The engine has such a flat torque curve that 5 speeds are more than enough. Go for the AX15. It's much cheaper than the NSG370 and it'll do the job better.

ok...but the 2005 Wrangler (the SE) that got the first 6 speed had a 4.0 I6...so whats the problem? I understand that it will be MUCH more expensive. But could you please tell me why it's not a good match for the engine?
 
He didnt say it would not be a good match, just unnecessary..
 
tealcherokee said:
id like to have a low, 4 gears and an over drive

you can never have too many gears

Yeah, except it's probably a "double overdrive" box, rather than a 1+4+1 (Granny + four + OD.)

If it's a double overdrive, then using it was probably more a marketing decision than anything else - chances are, you're not going to get any real use out of fifth and sixth, since they'll have your engine turning so slow at cruise that your mileage is going to SUCK.
 
The AW4 appears in Toyota Pickup, RWD Van, Celica, Supra, and RWD Lexus (which is just an overpriced Toyota anyhow.)

The XJ/MJ/ZJ version of the AW4 features an extra friction plate in each clutch pack to handle the loads that are more expected with trucks (towing, pulling, and the like.) This from a comparison of Toyota and Jeep parts catalogues.

Upon further reading, the NSG370 gives a "low" first gear of 4.46:1 and a Reverse ratio of 4.06:1, with a single overdrive (16%) and a "direct drive" fifth gear. The concept is sound, but the first gear could stand to be lower.

Also, I do now know what the bellhousing pattern on the 3.7L V6 used in the KJ is, so I'm not sure if it would fit. That's something else I plan to address when I finally get a line of communication open with DCX (Archival Tech.) If the 3.7L V6 and 242ci I6 do not share bellhousing patterns, then it falls to either make an adapter plate or cast a new bellhousing, if it is removable (given the current trend in manufacturing, it probably is.)

Now, if they'd given it a "granny first" in the range of 6.0-7.0:1, they'd be on to something. The SM465, as I recall, was a "1+3" box, with a low first gear down around 6.6 (or so):1 - you drove the thing like a 3-speed on the street (using 2, 3, and 4) and used 1 when you needed to pull a stump or something like that. With a dead low first gear, the NSG370 would effectively be a "1+5" box - driven like a five-speed until you need a low gear.

However, the relatively high overdrive may be more useful than the 25% or so overdrive found in the AX-15, given the trend in gearing. An interesting possibility - I may have to crunch some numbers later this week...

For those interested - 1/2/3/4/5/6/R"
4.46:1/2.61:1/1.72:1/1.25:1/1.00:1/0.84:1/4.06:1
 
Jeepthing88 said:
ok i've wanted to drop in a manual into my XJ for awhile now and I've found a few at the junkyard that have the AX-15 that will mate up with my 4.0 and my NP242 Transfer Case. Upon further thinking...I thought that if I'm gonna go through all the trouble of swapping in a manual, I'd really like to throw in a 6 speed. has anyone done this? is it even possible? from what research I've done the 6 speed in the newer jeeps is the NSG 370. Thanks for your help!!!


I just picked up a 2006 Unlimited with 4.0 and six speed. I can say this - I like the low first and extra overdrive gear. But unless someone makes a short shift kit for the NSG 370 I will not be putting one in my comanche instead I'll be sticking with the nv3350. The throw is just to long and it makes for some hard shifting. It's weird that the throw is so long because this tranny is out of the Mercedes M class and it's also used in the Crossfire which are both pretty sporty cars which would be dogs with such a long shift pattern.
 
i could have sworn that i saw somewhere that it was an extra overdrive gear and that it would make for better fuel efficency...

by the way all this info is great!!! thanks guys!
 
The concept is sound, but the first gear could stand to be lower.
==============================================
Someone uses this trany with a five to one first gear, Would be fine for all but the biggest of rocks I think. A few ODs out there for this box to.

==========================================
or cast a new bellhousing, if it is removable
=========================================
Sorry, Spit case with bellhousing

I would love one of the six speeds with a 5 to 1 installed for towing but the thing cost more then my trailer right now.
 
ok i think i made up my mind....though i agree with tealcherokee that you can never have too many gears...since I LOVE driving stick. but looking into the gear ratios and the overall cost i'm thinking its not worth it. The overdrive on the AW4 is .75:1, the overdrive on the AX15 is .79:1. So I'm already loosing some overdrive there. And then the overdrive on the 6 speed NSG 370 is .84:1. So though the 6 speed would be VERY COOL and from what I've been seeing something that has been done on very little, if any XJ's....I don't think that the sacrifice in the overdrive (not to mention the cost of the tranny) is worth it. Thanks for all your help guys!
 
the six speed ratios are:
Gear Ratios 1st - 4.46, 2nd - 2.61, 3rd - 1.72, 4th - 1.25, 5th - 1, 6th - .84, Reverse - 4.06

AW4 ratios are:
1st: 2.804 2nd: 1.531 3rd: 1.00 4th: 0.753

ax-15 ratios are:
1st: 3.83 2nd: 2.33, 3rd: 1.44, 4th: 1.00, 5th: 0.79

so you are gaining slightly more on the low end and loosing engine rpm in 5th

the six speed would be great but i cant really see using 6th gear all too often unless you like flying down the freeway at a low rpm (which isn't the most efficient rpm range for the I6).

its your money and i would love to see someone do it and report back. i don't really care for 6 speeds though, too much shifting. even with the new GTO, and the 6 speed in that, you cant accelerate worth a damn because your always shifting.
go here to see your final cruise speed and rpms for different transmissions:
http://www.grimmjeeper.com/gears.html
 
Last edited:
it seems from that conversion that the 5 speed is better than the 6 speed for daily driving....is its only true benefit the low 1st gear?
 
Jeepthing88 said:
ok...but the 2005 Wrangler (the SE) that got the first 6 speed had a 4.0 I6...so whats the problem? I understand that it will be MUCH more expensive. But could you please tell me why it's not a good match for the engine?

The 6-speed in the Wrangler coupled with 3.73 or 4.10 axle gears gives 1st gear an excellent crawl ratio. Even though it doesn't have a high enough ratio to make it a true granny low, functionally it IS, so the 6-speed would only be advantageous for rockcrawling and not much else.
 
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