Will a posi trac work well with a 3.31gear ratio that was orginally not?

are you on pavement, or offroad.?
99 Cherokee what transfer case?
if Part time system. then,.
are your tires on ice or dirt?
if not its cockpit error.
read the operators guide, on this.
if on ICE,say so, we can not know what transfer case you have
nor what tires are sitting on.
do tell, and we can tell you what good or bad.

here is the build list for these years XJ
what do you have. ?
The full time box, must not be in 4Lo , on pavement
unless it too is on ice .

All the transfer cases used on the Cherokee were chain driven with aluminium housings. Command-Trac was standard on XJ models built with 4WD.

• 1984-1987: New Process NP207 Command-Trac, part-time only, 2.61:1 ratio with low range
• 1984-1986: New Process NP228/229 Selec-Trac, full- or part-time, 2.61:1 ratio with low range

NP228/229 has a vacuum switch for 2WD-4WD selection on the fly and a separate manual lever for low range

• 1987-2001: New Process NP231 Command-Trac, part-time only, 2.72:1 ratio with low range

NP231 has the following settings: 2HI, 4HI, N, 4LO

• 1987-2001: New Process NP242 Selec-Trac, full-time or part-time, 2.72:1 ratio with low range

NP242 has the following settings: 2HI, 4 full-time, 4 part-time, N, 4LO

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never post questions on 4wd unless you know what is there.
the transfer case, also has tag , telling what it is.

4X4 actually provides power to the front 2, and the back 2.
Unless the back has limited slip or posi-track, if 1 wheel spins, the other will not turn.
Since the front wheels have to turn at different rates to accomodate turning radius differences, there is (usually) to limited slip on the front differential, so if one wheel spins, the other will not turn.
So, if you have one front wheel spinning at the same time as one back wheel is spinning, and you don't have posi-trac, you're stuck.
Cheerfuls.

try draining (check for metal) diff oil and adding new oil with additive. drive around making turns (figure 8 works best) if problem persists after 2 or 3 days check your brakes

the noise is coming from the clutch plates in the differential, i am assuming that it is posi-trac. and not a limited slip. you can get rid of this noise by draining fluid and replacing with proper differential fluid as recommended by manufacturer (go to gmc dealer parts dept.) also ask for posi-trac additive, use two bottles, the noise will not go away instantly, you will need to drive it for at least 500 mile before you notice change,

youd have to drop the differential covers in the junkyard til you found one with posi. posi was optional on the trucks.

C-Clip on end of axle!
Remove the Diff pin,push axles in and remove clips,pull axles.

Are you looking for a way to compress the posi clutch springs,also?

A little over three quarts.

It is possible, you just have to know what gear ratio you have in your Sierra. I had issues with my son's rear differential and did the Salvage Yard and picked one up for $250.00 with less then 45,000 miles. Remember new cars end up at Salvage Yards also.

Here are the Pro code for the rear ends to your Sierra and you can match one up at a Salvage Yard.
GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSI TRACTION)

HC4 -- AXLE REAR, 4.56 RATIO

Open Your glove box and look inside it. Should be a list of codes on the bottom.
Example: GU6 G80 According to that, you'll have a 3.42 posi

Good luck and keep me posted and call around Salvage Yards, there prices will differ from one to the next salvage yard and don't ask them for a posi rear end. The cost will you more, just search all the SUV's and look at the pro codes in the glove box. Hunt, most awd system SUV will have the G80 rear end.

Good luck and keep me posted.

One axle may have an open differential and the other a locked. If they both have the same gear ratio and the housing is identical you shouldn't have any problems. If you had posi and the new one doesn't, then you'll obviously lose that but it won't effect anything else.

Unless you have a Posi-Trac Rear end which you don't Only 1 Wheel turns. The Posi-Trac rear end is a Factory Option. You have got the Standard Option Rear end.