3278

Before I bought my XJ, the previous owner pulled the TC linkage and front driveshaft to install the leadfoot "simple TC linkage," but didn't get it all back together before selling it to me. So I've ordered the leadfoot upgrade myself, and I'm having a Tom Woods driveshaft built for me, but I'll get the TC linkage a month or so before the 'shaft.

So my question is - and it's really just curiosity - what will happen in each mode? I have an NP231, so I've got 2hi, N, 4hi, and 4lo. Here are my guesses, correct the wrong ones:

2hi: Nothing, normal mode.

4hi: The front fixed yoke on the TC will spin, but isn't hooked to anything, so not much happens. But the vacuum pump engages the front axle, too, and then... ?

4lo: The same stuff as happens in 4hi, except I'll be in 2hi, but again, what effect does engaging the vacuum pump to the front axle have?

SoCalxJ4.0

What's the point of shifting out of 2hi if you don't have a front driveshaft?

F1Addict

There's no point but I appreciate the curiosity. I'm curious, too.

OleBlue

2 hi, normal driving

4 hi normal driving but the yoke will be engaged, but it doesnt matter because its not hooked to anything. Your 95 does not have vaccuum actuated 4x4 in the d30.

4low you will be in 2wd with a 2.72 gear ratio to the rear wheels only. Dont drive over 15 mph in this mode! Its fun to play with though if you are offroad! Yoke will be engaged but again, wont hurt anything due to not being hooked up

3278

Awesome, thanks!

Now, about the vacuum-actuation: I've been a little bemused about what the vacuum actuator did since the beginning, except knowing that when mine sucked, I couldn't get out of 4WD. What does it normally do, and how does the 95 do that same thing without the vacuum? This is my fourth Cherokee, but my first this "new."

belvedere

Found this pic with a quick search. When actuated, the vacuum motor actually connects the two parts of the right axle shaft. Your '95 has no equivalent: the axle shaft is one piece, and just turns all the time.

SteveMongr

Maybe to smoke the tires in 2-Lo (4 Lo).
But, installing 4 doughnut spare tires is the funnest way to smoke all 4 .. Just keep an eye the RPM's

cruiser54

Thanks. I stole it.

belvedere

Thief!!

cruiser54

Yowzah!

Turbo X_J

Wad? 4 low = 4 wheel drive low ratio (actually about 3:1) to all 4 wheels. For an effective final drive ratio of ~ 10.65:1. Thats why:
1. It shifts like jack the bear.
2. Top speed is about 25 mph.

OleBlue

The low gear ratio in a 231, stock, is 2.72:1, as opposed to high, which is 1:1.

I dont know all the stupid math that goes into it but essentially, you will have 2wd LOW without a front driveshaft. Thats all I was saying.

Thanks for the useless input though, in case I ever need it.

3278

Damn. That's kind of what I was thinking. While that totally takes the whole "#$%@ VACUUM PUMP IS BORKED AGAIN!" out of the equation, isn't that going to hurt mileage compared to disengaging on the axle end? Hell, won't it mean my front driveshaft is always spinning, and only disengaged on the TC end?

Of course, I get 12-14 MPG anyway, 'cause I have big tires and haven't regeared and I drive like a gator bit me, but it's the principle of the thing, dang it!

PocketsEmpty

In theory, sure, it will negatively affect your gas mileage, but probably to a negligible degree. Since you already have your driveshaft out, do an experiment. Calculate your mileage while driving without the front shaft in. Then, hook up your front shaft and drive in 2wd as normal, and re-calculate. I'm willing to bet you won't find too much of a difference. And you are correct, your driveshaft and axle will always spin as long as you are in motion, there will just be no torque applied to it from the transfer case when in 2wd.

If this concerns you, the other option would be to convert to manual locking hubs, but that isn't cheap or practical for the D30.

Turbo X_J

I see what your saying now that you have explained it better, sorry it was late...