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Unread 07-27-2003, 09:16 PM   #1
f14x4
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Final Drive Ratio

THIS IS WHAT I WAS TOLD AND NOT SURE IF ITS TRUE.
THE 96 (MY YEAR) HAS 3:73'S FRONT AND REAR AND THE REASON
Y MY BROTHERS 98 IS FASTER AND MORE POWERFUL THAN MINE IS BECAUSE HE HAS 4:10'S
SO IS THAT THE TRUTH?
DID THEY CHANGE THE RATIOS IN 98?
AND IF THAT IS THE CASE, HOW MUCH WOULD IT COST IF I WERE TO GO TO A JUNKYARD AND GET THE GEARS OUTTA A 98?
ITS THE SAME T-CASE CORRECT? I KNOW I HAVE THE 35 IN THE REAR AND THE 30 IN THE FRONT.

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Unread 07-27-2003, 10:18 PM   #2
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Nope! Not true. Now I don't know what gears your brother has, but Grands NEVER came from the factory with anything lower than 3:73's. Someone could have put in 4:10's before your brother got his grand.
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Unread 07-27-2003, 10:28 PM   #3
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ALLRIGHT....I WASNT SURE IF IT WAS TRUTH OR NOT...
IT WAS ONE OF THOSE COULD BE SITUATIONS...I KNOW HIS GEARS WERE NOT CHANGED SO NOW IM BACK AT SQUARE ONE....WHY THE HELL IS MY JEEP SO DAMN SLOW AND UNRESPONSIVE!?!?!?!
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Unread 07-28-2003, 06:45 AM   #4
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While we try to figure it out, how about releasing your caps lock key?
It looks like you're shouting.
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Unread 07-28-2003, 01:42 PM   #5
Intrepidjeep
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Are they both Grand Cherokees, or is his a normal Cherokee? The normal Cherokees are a few hundred pounds lighter weight....

Do you both have the same engine? He may have a V8 while you may have a 4.0L six-cylinder?

If you both have sixes, I don't think there were significant power-related changes made to the 4.0L between 96-98. They made some refinements for '99 though...
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Unread 07-28-2003, 03:09 PM   #6
f14x4
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Quote:
Originally posted by Intrepidjeep
Are they both Grand Cherokees, or is his a normal Cherokee? The normal Cherokees are a few hundred pounds lighter weight....

Do you both have the same engine? He may have a V8 while you may have a 4.0L six-cylinder?

If you both have sixes, I don't think there were significant power-related changes made to the 4.0L between 96-98. They made some refinements for '99 though...
both inline 4.0's grand cherokees. the only thing im not sure of is which transfer case he has, and i have the 242. at this point that may be the only difference i am aware of, but i dont know if that would affect anything
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Unread 07-28-2003, 07:14 PM   #7
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Some possibilities

How about tires/wheels? Larger, heavier will have an effect on fuel mileage....

Maintenance? Old plugs & other ignition items are bad... A dirty air filter will hurt... O2 sensor maybe? Or a bad cat....

Another thought - does he have a manual trans, and you an auto? That would sure do it! (Note - was a manual available on a 4.0 98 ZJ?)
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Unread 07-28-2003, 10:12 PM   #8
f14x4
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Re: Some possibilities

Quote:
Originally posted by Stocker
How about tires/wheels? Larger, heavier will have an effect on fuel mileage....

Maintenance? Old plugs & other ignition items are bad... A dirty air filter will hurt... O2 sensor maybe? Or a bad cat....

Another thought - does he have a manual trans, and you an auto? That would sure do it! (Note - was a manual available on a 4.0 98 ZJ?)
yea i see where this is goin...my brother and i have identical jeeps....the only difference that we know abotu it i have rear view mirros that defrost and he doesnt. he has a back window that opens and i dont. he can recirculate his heat and i can only do my cold.
same tire size, same tranny, im not sure about the t-case, but i think he has the 242, which is what i have. we both have k&n air filters, stock box drop-ins. i have bosch platinum 4's which i recently was told arent that great in the 4.0 engine, but i know thats not the reason because he has the same plugs as well.

so far these are some of the things ive come across that may be possible reasons for the difference

1. the 4.0 in 98 has more horsepower--not true. power did not change until 2000
2. final drive ratio. possible differnet gearing. not true. gearing did not change over the 2 years.
3. possible tps adjustment. not true. setting is alrealy at .74 volts
4. dirty air filter. not true. cleaned, charged, lubed, and put back. no difference.
5. possible fuel filter. not true. replaced and no difference.


so now im goin back to basics. air flow is fine. no problem noted there.
the only thing i can think of is maybe my cat is clogged. im sure its possible with 120, 000 miles. so i have to look into that this weekend.
could it be possible for the timing chain to skip a tooth, and my timing be off? i know there supposed to be done every 60,000 and im at 120,000 now so im lookin to get it done anyway.
im gonna try to check the compression of the cylinders as well.

im ordering a tbs, high flow cat, and cat back but i really dont wanna put it back on until i fix the problem, cause whats the point of doin it if its only gonna restore power that it should have anyway.
the way im ridin now im getting about 11 mpg city and 14 highway, and my window sticker says 15 city 20 highway, i know its not gonna be the same now, 7 years later but i mean at 11mpg i shoulda got the 5.2, or the 5.9 for that matter

i havent had any codes at all, so im not worried about 02 sensors yet, but i have taken it into consideration.

so besides the cat being clogged and me testing compresion and timing im all out of ideas
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Unread 07-29-2003, 07:22 AM   #9
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Thanks for clarifying - I didn't know they were identical.

If the timing chain slipped, it would not run normally.

Compression test, good idea. Worn rings/valves would affect power and mileage. Speaking of which, you should be getting better than 11/14. Shoot, I usually get better than that with my 5.2!

Brings ya to the cat. They can fail a lot sooner than 120K. Mufflers can fail too and start collapsing internally, restricting flow. Good luck.
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Unread 07-29-2003, 03:38 PM   #10
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Timing chain supposed to be done every 60,000? You're thinking of timing belts on other engines, not timing chains. There's no actual maintenance to be done on a timing chain; you just deal with it when a problem becomes evident, or other major work needs doing.

I recall doing the following procedure on some engine or other to measure timing chain slack.

Take the distributor cap off and observe the rotor position. Put a nice long breaker bar with an appropriate socket to the crankshaft damper pulley. Slowly and carefully turn the cranshaft clockwise, and observe that the rotor starts turning. Mark the damper pulley position with a li'l chalk line or pencil line. Then rotate the opposite direction very slowly and stop immediately when the rotor starts to move.

If there is a lot of slop in the chain then you will have moved the crankshaft ten or fifteen degrees (or more) before taking the slop out of the chain after the reversal before the camshaft began to turn. Get the picture?? If there is 'normal' slack in the timing chain then you will see only three to five degrees of "reverse motion" before the distributor begins to turn.

If you are not sure how many degrees it turned during the procedure there is a simple way to calculate that based on the spacing between the chalk marks. Take a string and wrap it around the crankshaft damper where you made the chalk marks to measure the circumference of the damper. Let's say it was 18 inches. Then if there is one inch between the chalk marks then divide 1 by 18 and multiply the result by 360 (the number of degrees in a circle). In this case it would be 20 degrees of slack and it is time to replace the gears and chain! If the distance between the marks was 3/4", then calculate .75/18*360 and you'll get 15 degrees, still too much....

That's just an example -- all this depends on the diameter of your damper and how much distance between the marks is measured on your vehicle.

(By the way, the 4.0L was significantly reengineered in 1999, all of which yielded a very small power increase, so even if he had that engine it wouldn't do him a lot of good -- and keep in mind the '99-up Grand Cherokees are quite a bit heavier also. Upgrades included distributorless coil-on-plug ignition, new cylinder heads, new exhaust manifolds, a new 50% more efficient slitter-vane water pump, a new elastomer-coated steel intake manifold gasket, a two-piece high silicon-molybdenum alloy cast-iron exhaust manifold, automated belt tensioner and a new laminated oil pan. These refinements added about 10 bhp, a 5db quieter operation with an enhanced lower "throaty" sound quality, and cleaner emissions.)
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Last edited by Intrepidjeep; 07-29-2003 at 03:42 PM..
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Unread 07-29-2003, 06:17 PM   #11
f14x4
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Quote:
Originally posted by Intrepidjeep
Timing chain supposed to be done every 60,000? You're thinking of timing belts on other engines, not timing chains. There's no actual maintenance to be done on a timing chain; you just deal with it when a problem becomes evident, or other major work needs doing.

I recall doing the following procedure on some engine or other to measure timing chain slack.

Take the distributor cap off and observe the rotor position. Put a nice long breaker bar with an appropriate socket to the crankshaft damper pulley. Slowly and carefully turn the cranshaft clockwise, and observe that the rotor starts turning. Mark the damper pulley position with a li'l chalk line or pencil line. Then rotate the opposite direction very slowly and stop immediately when the rotor starts to move.

If there is a lot of slop in the chain then you will have moved the crankshaft ten or fifteen degrees (or more) before taking the slop out of the chain after the reversal before the camshaft began to turn. Get the picture?? If there is 'normal' slack in the timing chain then you will see only three to five degrees of "reverse motion" before the distributor begins to turn.

If you are not sure how many degrees it turned during the procedure there is a simple way to calculate that based on the spacing between the chalk marks. Take a string and wrap it around the crankshaft damper where you made the chalk marks to measure the circumference of the damper. Let's say it was 18 inches. Then if there is one inch between the chalk marks then divide 1 by 18 and multiply the result by 360 (the number of degrees in a circle). In this case it would be 20 degrees of slack and it is time to replace the gears and chain! If the distance between the marks was 3/4", then calculate .75/18*360 and you'll get 15 degrees, still too much....

That's just an example -- all this depends on the diameter of your damper and how much distance between the marks is measured on your vehicle.

(By the way, the 4.0L was significantly reengineered in 1999, all of which yielded a very small power increase, so even if he had that engine it wouldn't do him a lot of good -- and keep in mind the '99-up Grand Cherokees are quite a bit heavier also. Upgrades included distributorless coil-on-plug ignition, new cylinder heads, new exhaust manifolds, a new 50% more efficient slitter-vane water pump, a new elastomer-coated steel intake manifold gasket, a two-piece high silicon-molybdenum alloy cast-iron exhaust manifold, automated belt tensioner and a new laminated oil pan. These refinements added about 10 bhp, a 5db quieter operation with an enhanced lower "throaty" sound quality, and cleaner emissions.)
ok so ill try that as well...but as for your last paragraph about the 99, his is an 98 so that would not be the case either..
i had a suggestion today about the egr valve... so i guess im gonna check on that as well.
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