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Changing Gears; Ring And Pinion


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So this is what I got. 1991 jeep comanche with a full 2000 cherokee swap, there is a thread somewhere in here that I Showed her.

 

anyways. to what this topic is about,

 

I am running on front dana 30 3.54 gear ratio, and a rear dana 44 limited slip track lock differential with 3.54 gear ratio too. I have 285/75/16 tires, which come to about 33 inches.

 

I want to run either 4.10 or 4.56 gear ratio to get bettter gas/mileage, and for it to run smother too, and have a better response.

 

I am no expert on mechanics or anything, just a big fan of comanches, and cherokees, and some other jeeps. All I learned about jeeps has been here.

 

What I want to know is how do I know what type of ring and pinion I need?, low pinion, high pinion, thick, thin ring, etc without taking it apart since it is my daily driver.

 

and what is the best manufacturer to get this parts from.

 

I have found some good deals on ebay from motive gears, yukon gears, and expensive from dana/spicer, omix-ada.

 

any help would be appreciated.

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If your drive train came from a 2000 XJ (Cherokee), you don't have a dana 44 rear axle because the Cherokee didn't offer a Dana 44 in 2000. You would have either a Dana 35 or a Chrysler 8.25.

 

The 2000 Cherokee used a low pinion Dana 30 in the front. Up through 1999 they were high pinion, so be certain of what you have. It will make a difference.

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EDIT: Darn you Eagle!

 

 

 

 

 

The terms 'low' and 'high' pinion, as i understand them, refer to the position of the incoming pinion and don't really have anything to do with the physical gears themselves.

 

IF you also swapped the front axle out of that 2000 XJ you now have a low pinion Dana 30. 00 and 01 XJ are the only ones to come with a low pinion AFAIK. High pinion axles are preferred for their ground clearance. ALL 4wd MJs produced came with high pinion Dana 30s

 

Your rear axle is a low pinion, both Dana 44s and the more common Dana 35s are both low pinion axles.

 

 

As far as choosing a gearing ratio, one very critical detail that you didnt provide is what type of transmission you have.

 

IF you have an auto (the AW4) i would go with the deepest ratio you feel comfortable running. 4:56 sounds about right. The deeper the ratio the easier it will be on your trans to turn those larger tires of yours.

 

 

IF you are running a stick/manual/AX-15 you could get away with a little less.

 

Personally i think 4.30s would be a good ratio no matter which trans you have.

 

 

For your viewing pleasure. . .

 

131_0602_08_z%2Baxle_tech_info%2Bhigh_lo

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If the drive train is original MJ stuff you need a front gear set for a high pinion Dana 30. They are also called "reverse rotation." The gears are not the same for a low pinion so if it is a 2000 you need a low pinion gear set. To go from 3.54/3.55 to either of those ratios you mentioned you will need to replace the carrier. You can get a factory carrier or take the opportunity to upgrade to a Truetrac or other full carrier locker.

 

For the rear it should be a low pinion 44. High pinion axles are almost exclusively found in front axle applications. Normally you would also need to change your carrier for that gear swap which would cost you your limited slip. (In Jeeps the LSD is Track Loc. Posi is a Chevrolet term.) However for low pinion D44's you can get a "thick" gear set that would allow you to keep your factory LSD and save you few bucks in the process. If you want to upgrade the carrier to a full case locker like a Detroit, though, now would be the time. If you do you would then use thin gears. If by "full 2000 swap" you meant the drive train then the rear would not be a D44. If it is a Dana 35 throw it away and spend $100 on a used 8.25 and start from there. 8.25's use the same carrier and gear sets for all ratios.

 

If you did mean the common cosmetic only swap please do not include that in questions like this as it is irrelevant and just causes confusion.

 

As to ratio it really depends on what is more important to you. You can go to WWW.grimmjeeper.com and plug in the stock numbers in one column and then try different combos in the other column to see what ratios get you the RPMs that you want. To split the difference as recommended above remember that 4.27 & 4.30 are matching ratios. Those ratios may not be available for your particular application.

 

Cheap gear sets like US Standard tend to make noise which is most often a whine that can get annoying. Better sets like Yukon generally do not. Companies like Motive have two lines as well. There are many brands so you may want to Google the rep of any set you are interested in.

 

If your axles are swapped in all bets are off on this info. If they are and you can post info as to the original application or even front and rear pics of the axles we could make appropriate recommendations.

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My suggestion: 1st I agree with all above, next who will be swapping the gears? If a shop is doing it, I would have them source all parts and materials so as to have no warranty issues with parts you provided. You can have them order up what ever brand you choose. If you, a friend etc sets up the gears then its whatever your wallet and other factors (opinions) steers you to buy.

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4.56 gears and 285/75/16 tires will yield about 2500 rpm at 65 (this is the exact combination I am running). If you are going to run 33" tires, lift is involved/required. Drive line angles get critical when you spin them this fast. In the above mentioned combination, the drive line is knocking on the door of 3000 RPM at 70. If everything is not right, she's gonna vibrate. Just something else to be aware of.

The power/response is good with 4.56, fuel mileage, not so much. 

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thanks for all your answers.

It was kinda late when I posted and was a little bit tired. And yea I meant a full cosmetic 2000 change, not drivetrain. Drivetrain is originally 1991. front and rear.  I'm sorry for the confusion.

 

so my understanding is that i will use front high pinion and rear low pinion.  and thick ring for rear.

 

and I'm running a automatic aw4 trans from the 2000 cherokee... also engine is 2000.

 

so to Incommando; I do have to change carriers then to go to that gear ratios? what gear ratios would be better like, 4.10? 4.30? to keep factory carriers..

 

I can't spend that much right now, I was thinking of doing this swap for like 400 dlls total, I would be taking this to a shop, but they want me to bring the parts. or at least they said it would be cheaper that them ordering them and installing. 

 

I will post pics later in the week as my truck is right know on rear disc brake conversion... well it is done, but they are doing the engine, trans, oil hcange too. 

 

it should be done by tomorrow and will take pics of dravetrain....

 

 

as the webpage WWW.grimmjeeper.com... I was putting numbers and my understanding is that 3.54 gears give better mileage than 4.56... i am kinda lost here, I thought it was the other way around, that it will travel farther with shorter gears (bigger numbers) than with taller gears (lower numbers)...anymore explanations... 

 

if it is this way am I supposed to keep what I have then?

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ok... I read the article on the grimmjeepers.com page "The basics of gears and why you would want to change them" and what I understand of it, I think is better now, is that for one tire rotation my shaft has to turn 3.54 times... so higher number gear ratio (shorter gears) = higher rpm, better acceleration, bad fuel economy, less top speed..... lower number gear ratios (taller gears) - lower Rpm, better fuel economy,  lower acceleration more speed.

 

So to other table that I found on morris,

 

http://www.jeep4x4center.com/jeep-tires/tire-gear-ratio-chart.htm

 

As my calculations Comanches ran around 28 inches tires stock, so with 3.54 gears they made 2769 rpm at 65 mph ... so to get those numbers it would have to go to 4.11gear ratio using 33"s ...

 

so as I understand to return to "stock configuration " it would be 4.11 but my fuel economy would not get better, since I'm doing 2349 rpm at 65 mph on highway by reading the table.

 

any ways am I right? or what do you guys think?

 

I don't go that much wheelin, I live in brownsville texas, what we have over here is sand, so I don't go that much becuase of rust get quickly on cars. I do daily driving and around town, I just have the looks of a really bad  @$$ 4wheeler.

 

 I need good speed/good fuel economy/ give a good care to the motoor with big wheels, this is what is concerning me the most... am i making it run harder to move?

 

here is a topic I had with pics.

 

http://comancheclub.com/topic/36167-jeep-comanche-roof-basket/?do=findComment&comment=361911

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Just because RPM is higher does not necessarily mean worse gas mileage. If the RPM is low, but your straining the engine, your still pouring alot of fuel into the engine to keep it running, versus running at a higher RPM with less engine strain. There is a balance, and I think ideally it's best to keep with stock rpm to speed ratios to maintain fuel economy to some degree. With bigger tires, you have more mass to move, you WILL lose efficiency, plain and simple. Go with the gear ratio that gets you closest to stock RPM to MPH. 

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Stock ratios are generally a compromise between power and MPG. Returning to a stock RPM level will return you to near stock levels in each but probably not completely. A taller rig is less aerodynamic. In addition larger wheels and tires weigh more and that weight is unsprung. Unsprung weight has the most effect on performance and MPG. A rule of thumb is that 1 pound of unsprung weight equals adding ten pounds of weight supported by springs. Basically that means that making a rig taller and heavier will make it hard to keep the same MPG. For a lot of highway driving you might go to 3.73's to lower highway RPM's. As you do mainly around town driving and if you were happy with the truck's performance when stock then 4.10's/4.11's look good. 4.56's should give you more punch light to light and off-road but at a cost in MPG. I don't think they make a 4.27/4.30 for a high pinion d30 but if they do that ratio would give you more punch then the 4.10's with less MPG loss than 4.56's.

 

A rear thick gear set would save you a carrier swap in the rear but none of the gear changes would prevent the need for a front carrier swap. The "ratio break" for the D30 is 3.73. 3.73 and numerically higher gears take one carrier while 3.55 and lower take another. The break for a 44 is 3.92-up. You could go to a 3.73 and use a thin gear set on the stock carrier but that is it.

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thanks for all your answers.

It was kinda late when I posted and was a little bit tired. And yea I meant a full cosmetic 2000 change, not drivetrain. Drivetrain is originally 1991. front and rear.  I'm sorry for the confusion.

 

so my understanding is that i will use front high pinion and rear low pinion.  and thick ring for rear.

 

and I'm running a automatic aw4 trans from the 2000 cherokee... also engine is 2000.

 

so to Incommando; I do have to change carriers then to go to that gear ratios? what gear ratios would be better like, 4.10? 4.30? to keep factory carriers..

 

I can't spend that much right now, I was thinking of doing this swap for like 400 dlls total, I would be taking this to a shop, but they want me to bring the parts. or at least they said it would be cheaper that them ordering them and installing. 

 

I will post pics later in the week as my truck is right know on rear disc brake conversion... well it is done, but they are doing the engine, trans, oil hcange too. 

 

it should be done by tomorrow and will take pics of dravetrain....

 

 

as the webpage WWW.grimmjeeper.com... I was putting numbers and my understanding is that 3.54 gears give better mileage than 4.56... i am kinda lost here, I thought it was the other way around, that it will travel farther with shorter gears (bigger numbers) than with taller gears (lower numbers)...anymore explanations... 

 

if it is this way am I supposed to keep what I have then?

 

 

The only thing I have to add.........

 

 

Any QUALITY shop will charge you in the neighborhood of $800 to regear both axles.

 

The only way you will swap out both for $400 is if you find the gears used and you do the work yourself. Oil, seals, gasket maker.......that alone will run you $50+........not to mention bearing that you may need to replace.

 

 

There is a thread here, Bluecomanche.......IIRC......... who had his front regeared and had to take it back three times......brake failure and his gears were 'singing'........this is not something you want your corner redneck shop to throw together and cheap is not cheap.

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ok thanks for all your answers. So with the calculations of the grimmripper web page I came to 4.17 which is either 4.10 and 4.30, as you all mention 4.30 is not made for jeeps. so I will have to change carriers and that will not make my budget. I might go 4.10.

 

however I just did the rear disk brake conversion and it took a load on my budget, since I have to change bearings once, seals twice, oil seal retainers twice, and preload spacers, etc some other things, thats why I was thinking around 400 to 500 the most. I think I can do that in a good shop, since I leave in the border of USA and Mexico and there are good shops that if you bring the parts they will change anything for low cost labor. thats why I think I can do this with a low budget.

 

on the other hand, 4.10 for rear dana 44 could be done as you say, but as the dana 30 I think I saw some on ebay,  I just have to find a good quality one on there.

 

SO in the end, I might go 4.10 ust to come close to "stock" to get a better punch from the truck and a little better mileage of gas if not the same but better acceleration.

 

I will track down the parts, and get you guys pictures of the differentials so I can get more advice on this.

 

thanks a lot to everyone for now. I will keep you posted.

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Show us a picture of the rear differential from the rear, so we can see the shape of the diff cover and the bolt pattern. I'm not getting a warm and fuzzy feeling that your rear diff is a D44 like you think it is.

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well I am pretty sure it is a d44, I have gotten all sort of parts for it showing D44 on the listing of every store, and the have matched, so It would not make sense that it is not. but anyways here is the picture, also I have compared with the picture/drawing that has all the covers on it.

 

also the new gasket for the cover was for dana44 too, so I'm pretty sure it is what i think it is.

 

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lol.... thats how I bought the truck, It did not came with it and with the lift it would have not fit anyways... I was in the process of making a new one, but just had a friend put some zip ties so that the valve perfoms as it was supposed to work without load.

 

But in the near future and now with the new rear disc brake conversion I am going to take it out, just have to find the time to do the job. lol...

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