Topic: looking to put in a 6 speed manual

[brokenwrist21]

ok folks, i have a 93 yj with the 2.5l ax5 and i have decided that eventually i would like to have a 6 speed, for fuel economy reasons. my only problem is that the nv4500 is huge and would require modifing the trans tunnel, not wanting to do that. the other option is to use a nv3550 but the bell housing is only for the 4.0 does anyone know of a 6 speed that will bolt right up. still have the original 231j t-case

[enginethatcould]

If you want to run the nv 3550 behind your 4 banger you can with a few parts. You will need a dakota bell housing as well as a chevy clutch. You will also need a few other pars but it can be done with a fair amount of ease. Google the swap are search here and pirate. I currently run one in my 93 and have no complaints. If you have any questions feel free to ask.

[sharpxmen]

nv3550 is 5 speed not 6 speed, the Jeep 6 speed was behind the 2.4L engine and i don't think there is a bellhousing that would bolt it to the 2.5L

[Jeffy]

The 2.4L shares the 4.0L bell housing bolt pattern which isn't the same as the 2.5L.

[Bounty Hunter]

You're not going to see any mileage gains, lotta trouble for no gain.

[Jeffy]

You're not going to see any mileage gains, lotta trouble for no gain.

Correct.  People think the only difference between a 5-speed and a 6-speed is that there is a double OD.  There isn't.  The gears are set up closer and the extra gear is usually between 3-4 or 4-5.  5th is 1:1 and 6th is OD.  Any mileage increase or decrease would come from not having to rev up as much as you would with a 5-speed.

[brokenwrist21]

with 4:88's at 70mph i'm turning about 3000rpms in 5th, i figured that having a 6 speed would drop my rpms lower to ease the strain on my engine. i've put the yella terra roller rockers on, a rv cam, msd 8.5mm super conducter wires, bosch platinum +4 plugs, 4.0 tb, spacer, removed the air venturi from the air tube, synthetic oil, k&n air filter, synchromesh transfluid, and synthetic transfer case oil. all in an attempt to increase power & fuel mileage.

[aw12345]

You would actually rev a little higher compared to an NV3500, the 6 speed has a bit less of an overdrive ratio than the 5 speed. It does have a nice granny gear and a very nice gear spread though

[sharpxmen]

lower rpm doesn't necessarily mean better mpg

in this case you'll be around the same rpm in 6th that you are in 5th with your current transmission for a given speed.

[Bounty Hunter]

3000k at 70mph is probably best for your mileage and being able to maintain speed, much less and the engine will be lugging and using more fuel.  Sharpxmen is right, lower RPM doesn't automatically mean better mileage, especially with a less powerful engine like the 2.5L that likes high RPM's.

[brokenwrist21]

my mileage is about 14.3 used to be about 16-18 with the factory 4.11s. so i figured with a 6 speed i could drop the rpms and be able to cruise better. i can watch my fuel gauge drop when i'm running 70. my motor actually prefers to run at about 2500 or so. it pulls strong through about 3000, after 3000 it drops off until i shift gears, and bring the rpms down

[Torch_Ind]

my mileage is about 14.3 used to be about 16-18 with the factory 4.11s. so i figured with a 6 speed i could drop the rpms and be able to cruise better. i can watch my fuel gauge drop when i'm running 70. my motor actually prefers to run at about 2500 or so. it pulls strong through about 3000, after 3000 it drops off until i shift gears, and bring the rpms down

running over 70 will cause fuel consumption in a square box regardless of your rpm.  your foot is going to be throw the floor to keep those speeds

[Jeffy]

As mentioned numerous times.  Here's the actual gear ratios for both;

NSG-370 are: 4.46, 2.61, 1.72, 1.25, 1.00, 0.84
AX-5 are: 3.93, 2.33, 1.45, 1.00, 0.85

4th on the AX-5 and 5th on the NSG are BOTH 1:1.  Overdrive is almost identical.  Like I said before a 6-speed is not a 5-speed with an additional gear after Overdrive.  It does not have an additional overdrive.

Manuals with Overdrive only have ONE additional gear after 1:1.  The second to last gear is almost always 1:1.

[Torch_Ind]

As mentioned numerous times.  Here's the actual gear ratios for both;

NSG-370 are: 4.46, 2.61, 1.72, 1.25, 1.00, 0.84
AX-5 are: 3.93, 2.33, 1.45, 1.00, 0.85

4th on the AX-5 and 5th on the NSG are BOTH 1:1.  Overdrive is almost identical.  Like I said before a 6-speed is not a 5-speed with an additional gear after Overdrive.  It does not have an additional overdrive.

Manuals with Overdrive only have ONE additional gear after 1:1.  The second to last gear is almost always 1:1.

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