Re-gear: Final questions before install

[Jamison C]

I have the 4.0, 33s, and the NV3550. I regeared to 4.56 from 3.07 and love it.

However, after learning the characteristics of the 4.0, if I were to do it again I would go 4.88. That would put me at 3k rpms at 75mph, right at the peak of the 4.0s powerband.

It also depends on where you live. I live in northern AZ where there’s tons of hills and mountains. So I want the peak crawl/cruising ratio for off-roading and highway.

I also start in second gear from stops. I have to ride the clutch just a tad to make it happen but it works. If I start in first gear I have to shift halfway through the intersection. But if I had 4.88s second gear would be a nice smooth gear to take off from at dead stops.

 

[Grey_Machine7.3]

All of these reasons are why I'm going 4.88 when I'm able

 

[chino1969]

I have the 4.0, 33s, and the NV3550. I regeared to 4.56 from 3.07 and love it.

However, after learning the characteristics of the 4.0, if I were to do it again I would go 4.88. That would put me at 3k rpms at 75mph, right at the peak of the 4.0s powerband.

It also depends on where you live. I live in northern AZ where there’s tons of hills and mountains. So I want the peak crawl/cruising ratio for off-roading and highway.

I also start in second gear from stops. I have to ride the clutch just a tad to make it happen but it works. If I start in first gear I have to shift halfway through the intersection. But if I had 4.88s second gear would be a nice smooth gear to take off from at dead stops.

Thanks for taking the time to respond. The take off from an intersection in 2nd gear being a nice smooth transition sounds much better. Will talk it over with the shop and post on the answer.

 

[chino1969]

@jjvw explained it all but yes, less downshifting when climbing, a bit quicker upshifting from a start. Off road in 4lo, it will crawl nicely with less gas pedal and descend more controllably with less or no braking.

Thanks for the detail; that is precisely what I was looking for. Appreciate it.

 

[chino1969]

I want to thank everyone who took the time to respond to my questions. It really helps especially coming from those who have been there, done that. I'm new to this particular game and am trying to get up to speed, make the right decisions and spend the money once to get precisely what I want. Now if anyone wants to know about precision long distance shooting, building AR's, the quality of various rifle components or world class gunsmith recommendations, I'm in my element and feel free to ask on another forum. Will keep everyone updated on this thread because if I learned new info. there are many others who will be making the same decisions and can benefit from the shared experience. Keep the info. coming. I now have a much better understanding of why 4.88 gears are recommended by some.

 

[chino1969]

Finally re-geared to 4.56 with 33" tires along with a Detroit Tru Trac in the Dana 44 rear. For now the front will remain an open diff. until a locker is warranted or needed. Was considering 4.88 gears after reading different opinions but stayed with 4.56 gears. Thus far, I am satisfied and notice a considerable difference. The gears are G2 with the complete installation package which includes new bearings, axle seals, pinion seals, pinion nuts and hardware. Very satisfied with the quality and workmanship of the shop that did the work. Thanks to Westown Willy for recommending the JP Shop in Chester Springs, PA.. Will do the 500 mile break in and change the diff. fluid then. It is becoming hard to find diff. fluid without the LSD additive but have managed to find Valvoline High Performance and Chevron Delo Gear ESI without the friction modifier. It is important to note that Valvoline High Perf. 75W-90 has friction modifiers added whereas the 80W-90 & 85W-140 is not shown as having friction modifiers per Valvoline specs.

https://sharena21.springcm.com/Publ...2d889bd3/76f88e7f-fbbc-e711-9c12-ac162d889bd1

 

[Grey_Machine7.3]

Finally re-geared to 4.56 with 33" tires along with a Detroit Tru Trac in the Dana 44 rear. For now the front will remain an open diff. until a locker is warranted or needed. Was considering 4.88 gears after reading different opinions but stayed with 4.56 gears. Thus far, I am satisfied and notice a considerable difference. The gears are G2 with the complete installation package which includes new bearings, axle seals, pinion seals, pinion nuts and hardware. Very satisfied with the quality and workmanship of the shop that did the work. Thanks to Westown Willy for recommending the JP Shop in Chester Springs, PA.. Will do the 500 mile break in and change the diff. fluid then. It is becoming hard to find diff. fluid without the LSD additive but have managed to find Valvoline High Performance and Chevron Delo Gear ESI without the friction modifier.

I ordered several gallons of Lucus gear oil off Amazon that doesn't have fiction modifiers in it

 

[Grey_Machine7.3]

I ordered several gallons of Lucus gear oil off Amazon that doesn't have fiction modifiers in it

Just be sure to get one of those "slippery Pete" gallon jug oil pumps. You'll have to add one of the smaller hoses to the bottom of the pump. Had my friend fill up the rear "uhm it's not pumping anymore" whoops. Works great after putting on the hose like I should have to begin with hehe

 

[chino1969]

I ordered several gallons of Lucus gear oil off Amazon that doesn't have fiction modifiers in it

The Tru Trac depends on the correct coefficient of friction bias to operate properly. The trait that sold me on it was it does not have a component that needs to be rebuilt every so many miles. I looked at STP diff. fluid today at Auto Zone and could not find anywhere saying it had friction modifiers for LSD's.

 

[chino1969]

Just be sure to get one of those "slippery Pete" gallon jug oil pumps. You'll have to add one of the smaller hoses to the bottom of the pump. Had my friend fill up the rear "uhm it's not pumping anymore" whoops. Works great after putting on the hose like I should have to begin with hehe

Yeah, I'll either get a gallon or two of the Valvoline or the Chevron Delo Esi.

 

[Jerry Bransford]

The Tru Trac depends on the correct coefficient of friction bias to operate properly. The trait that sold me on it was it does not have a component that needs to be rebuilt every so many miles. I looked at STP diff. fluid today at Auto Zone and could not find anywhere saying it had friction modifiers for LSD's.

Absolutely not, a Truetrac needs absolutely no friction modifier additive since it is gear-based, not clutch-based. Only clutch-based LSDs like the Tracloc require a friction modifier additive.

But it's a moot point since most gear lubes already contain the friction modifier additive, very few do not. It's the back label that will confirm the presence of the friction modifier additive by saying something like "Compatible with limited slip differentials" which means it has the friction modifier additive clutch-based LSDs require.

 

[chino1969]

Absolutely not, a Truetrac needs absolutely no friction modifier additive since it is gear-based, not clutch-based. Only clutch-based LSDs like the Tracloc require a friction modifier additive.

But it's a moot point since most gear lubes already contain the friction modifier additive, very few do not.

Perhaps my wording was incorrect. This is what I meant to say:

Lubrication Specifications
Detroit Truetrac�
High quality mineral or synthetic gear lubes are
required for use in Detroit Truetrac differentials.
Regardless of the lube type, always use a GL5 rated
lube with the least amount of friction modifier. Mineral
lubes lacking friction modifiers (limited-slip additives)
were historically recommended for all Truetrac
applications because friction modifiers can slightly
reduce the bias ratio (limited-slip aggressiveness) of
Truetrac differentials.

There are still diff. fluids to be found without the friction modifiers, ref. Chevron Delo 80W-90 ESI Gear Oil.

https://cglapps.chevron.com/msdspds/PDSDetailPage.aspx?docDataId=76979&docFormat=PDF

 

[Grey_Machine7.3]

Conventional gear oil has been said to run cooler than synthetic.

 

[chino1969]

Conventional gear oil has been said to run cooler than synthetic.

Since I re-geared I have been checking the temp. of the rear diff. after driving for 20 minutes by hand. I can't believe how hot it gets. It has conventional non synthetic gear oil in it and that is what I will stick with. I would have never known about this without reading the advice on this site. With that in mind, would it be advantageous to go with a higher vis. fluid like 85W-140?

 

[Westtown Willy]

Since I re-geared I have been checking the temp. of the rear diff. after driving for 20 minutes by hand. I can't believe how hot it gets. It has conventional non synthetic gear oil in it and that is what I will stick with. I would have never known about this without reading the advice on this site. With that in mind, would it be advantageous to go with a higher vis. fluid like 85W-140?

First, congratulations on the re-gear, there's nothing like proper gearing to make the TJ feel as it should.

Regarding the fluid, I've been using this stuff since my re-gear. I change it once a year in the middle of the summer when it's hot as hell, leave the bottles in the driveway to get good & hot so it runs easily, changed it once when it was cold out & this shit runs like pudding going up hill:

Now on to more important business, since you're all geared up proper it's high time you get that pig out onto the trails - by my calculations you oughta be all broken in by October 26 so you've got no good reason not to join us at AOAA

 

[chino1969]

First, congratulations on the re-gear, there's nothing like proper gearing to make the TJ feel as it should.

Regarding the fluid, I've been using this stuff since my re-gear. I change it once a year in the middle of the summer when it's hot as hell, leave the bottles in the driveway to get good & hot so it runs easily, changed it once when it was cold out & this shit runs like pudding going up hill:

View attachment 116698

Now on to more important business, since you're all geared up proper it's high time you get that pig out onto the trails - by my calculations you oughta be all broken in by October 26 so you've got no good reason not to join us at AOAA

Well thanks for the recommendations on using the JP shop. They will definitely have mu business going forward. Hope to be able to join you at AOAA.

 

[Stevo64]

I’d put the matching truetrac in the front.

 

[Jerry Bransford]

I’d put the matching truetrac in the front.

As one who first installed front and rear Truetracs 25 years ago, I can think of nothing more useless on uneven trails like the OP mentioned, which is true on our rocky SoCal trails too. It was less than a year before I replaced both Truetracs with lockers. Nothing improved my TJ's offroad abilities more than having done that.

I'd choose Truetracs for icy or other similarly slick surfaces but never for typical offroad needs.

 

[Stevo64]

Lockers are the best in really rocky places. Selectable is best overall. But truetracs front and rear help a lot. Better than open or a clutch pack LSD

 

[GPK03X]

O.K., one last time for any input and for confirmation I am making the right decision. I have a 2004 TJ 4.0l, NV3550 5 speed trans. with 33" tires and 3.73 gears, Dana 44 rear, Dana 30 front. Shifting on the road is less than desirable, especially going up hills. This will see some off road like forest trails and moderate off road use. This will be my daily driver for awhile, I live in PA where we get snow. I have decided to go with 4.56 gears and a Detroit Tru Trac LSD in the rear. I was going to go with an auto locker in front but changed my mind when reading about the handling quirks in the snow, so the front will remain open diff. until I see a need to do something different. I can't justify air or electronic lockers for my intended use. I believe an LSD in the rear will do everything I expect or need. Any opinions greatly appreciated. Understand I am very pragmatic and don't need to spend money where it is not needed. Thanks.

I’ve got 4.56 with 32’s and it’s great , but of course now I’m thinking 33’s and wish I would have gotten 4.88