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Discussion Starter #1
Hi all,
I'm starting on the planning phase of my next big project and I would like to tackle the differentials.

For starters, my current setup is a stock Dana 44 front / Ford 8.8" rear with 3.55 open differentials.

After spinning my tires climbing out of a hole last summer, and tearing chunks out of my tread, I figured it's time for some traction control.

Since this is a daily driver, and we have snow and ice in the winter, I'm not super sold on lockers. Even a selectable locker seems like a trade-off since it's still an open diff when it's off. I don't do any hard core wheeling, so I am thinking something along the lines of a TrueTrac. I remember posing this question a while back and that was a suggestion that seemed like a good idea.


Now, the question I have about the rear. I have an 8.8" under the Bronco right now, but I also have a 9" axle sitting in my garage. Would it be better to simply pull the 8.8" off and upgrade it? Or should I go with the 9"? Would the 9" swap right in afterwards? Or would have I have to do other tweaks, like changes to the driveshaft, brakes, shocks, etc.? If it's too much trouble, I'll just go with the 8.8" and not worry about it but wanted to get an opinion.

Secondly, I've toyed with the idea in the past of upping the 3.55 to a 4.11.
I have 32" tires and with the ZF5, I have a 0.76 overdrive. With 4.10s, I'd only be at 2600 RPMs at 80mph, which is pretty decent. Currently, I'm at 2250, which I do have to say is pretty nice since it keeps engine noise and gas consumption down on long trips. It also doesn't struggle with the 3.55s at all, and I'm be happy with them.... but the 4.10s just seem like they'd be so much fun. 3.73s are a good middle ground, but don't seem worth the trouble.

I've read and watched a number of tutorials on setting gears, and it seems totally doable, but is there anything I need to watch out for with this idea?

Thoughts overall?
 

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My diff guy here in Colorado recommended TruTrac or another non-clutch limited slip for snow, so I'm going TruTrac rear, Nitro Helical front, 32" tires and 4.10- but I have a C6. With overdrive, 4.10 would be solid, but really for best efficiency see where your cams' torque curve is and try to match your gear/tire selection based on that.
I've read alot that the 9" really isn't any stronger than the 8.8, but there are many opinions on that. I'm putting some HD axles in my 8.8 for piece of mind, but properly set up 8.8s last a long time if you don't throw too much power at them.
 

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If it is not a Bronco, it's just not worth driving.....
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I think the first question you should answer is are you satisfied with your current tire size? If you are then plan your diff to what you currently have on your truck. But, if you are even considering going up to 35's then I would wait and upgrade tires and diff's at the same time. I'm sure you know you you have to do front and rear at the same time.

I would suggest you put in e-lockers. I went with a Grizzly Yukon locker which is a full time friction plate locker. It works very well but it pops and crackles on turns but not bad enough to be a problem. I wish I had put in e-lockers on both diff's when I did mine.
Eventually I will put in an e-locker up front so I have a true 4x4 instead of my current 4x3.

Just my 2 cents worth
 

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Premium Member
1989 Eddie Bauer 5.8, C6, True Trac diffs, 4.56 gears, 4" C&T lift, 130A 3G Alt, 35" Grabber AT2s
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You saw mine a year ago in Moab. 4 inch lift with C&T beams. 4.56 gears on Detroit Tru Trac carriers. i do more daily driving than rock crawling, mostly around town. My truck has a C6, and to be honest, I wish now I had gone with 4.11s. My 5.8 runs along at about 3800 RPMs at 75, practically screams. As for the strength of the 8.8, most guys that upgrade go to bigger 3/4 or 1 ton axles. 10.25 amd 10.5 inch ring gears. Seems overkill for the type of stuff you do.

Welcome back.
 

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Discussion Starter #5
My diff guy here in Colorado recommended TruTrac or another non-clutch limited slip for snow, so I'm going TruTrac rear, Nitro Helical front, 32" tires and 4.10- but I have a C6. With overdrive, 4.10 would be solid, but really for best efficiency see where your cams' torque curve is and try to match your gear/tire selection based on that.
I've read alot that the 9" really isn't any stronger than the 8.8, but there are many opinions on that. I'm putting some HD axles in my 8.8 for piece of mind, but properly set up 8.8s last a long time if you don't throw too much power at them.
That was my thought on going with a limited slip. I want it capable for the snow, rain, etc. and year round driving weather. Plus, I really like that the truetrac doesn't rely on clutches, etc. that wear out.

I wish I had specifics on the cam's peak. It just has an RPM range listed in the specs. But I would think it's somewhere around 2300 - 2700 RPMs, so anywhere in that range is decent.

That's my thought on the 8.8. The only real perk to the 9" is that it's currently out. Granted, I'll have to pull the front either way.
I'm thinking of doing what you're saying as well and rebuilt the whole rear with HD axles, new bearings, etc. while it's all apart, if I go with the 8.8".
I also read that the 8.8" gets better gas mileage (if only slightly) due to the way the gears mesh.

I think the first question you should answer is are you satisfied with your current tire size? If you are then plan your diff to what you currently have on your truck. But, if you are even considering going up to 35's then I would wait and upgrade tires and diff's at the same time. I'm sure you know you you have to do front and rear at the same time.

I would suggest you put in e-lockers. I went with a Grizzly Yukon locker which is a full time friction plate locker. It works very well but it pops and crackles on turns but not bad enough to be a problem. I wish I had put in e-lockers on both diff's when I did mine.
Eventually I will put in an e-locker up front so I have a true 4x4 instead of my current 4x3.

Just my 2 cents worth
Yeah, I really like the tire size I have. It makes for a nice daily, doesn't require a lift, looks good, and they're big enough to allow me to go the places I like to go. I have no real interest in going with anything bigger, so the 32s are for sure.

And no worries, if I do gearing, it'd be front and rear.

Personally, I think a full locker is just overkill for what I do. And then having it turn off would mean an open diff again when I'm not using it. The limited slip would be year round, which would be nice, and is a good middle ground between the two.

You saw mine a year ago in Moab. 4 inch lift with C&T beams. 4.56 gears on Detroit Tru Trac carriers. i do more daily driving than rock crawling, mostly around town. My truck has a C6, and to be honest, I wish now I had gone with 4.11s. My 5.8 runs along at about 3800 RPMs at 75, practically screams. As for the strength of the 8.8, most guys that upgrade go to bigger 3/4 or 1 ton axles. 10.25 amd 10.5 inch ring gears. Seems overkill for the type of stuff you do.

Welcome back.
Yeah, if I still had the NP-435 I don't even think I'd be considering the 4.10s. I just don't like my RPMs that high for how often I drive it. 3800 would drive me crazy! I think 2600 in overdrive would be decent still, along with the boost the 4.10s would give over the 3.55s. That's a good 16% increase.

But yeah, an 8.8" is plenty for what I do. I usually have camping gear in the back, and am just trying to get somewhere remote. Not putting it to the test. :D
 

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I switched mine last year to true-trac front and rear (4.10 rear and 4.11 front) before Bronco Safari. I'm happy with it, running 33" tires.
 

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Discussion Starter #7
I know this question has probably been asked a dozen times, but what gears brand does everyone prefer?
Again, I don't wheel hard, but I don't want cheap either. I've also heard some of the more heavy duty ones can really whine, which I don't want.

Thoughts?
 

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78 & 92
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You can buy dana/spicer gear sets for the front from JBG (and others) now. That is what I used, recently
I also went with a trutrac in my 92 and it works great, have one up front in the 78 too but have not really tested it out yet.
9" swap you may have to remove the flange yoke if your 8.8 has a flat flange at the pinion. No big deal, just something. I swapped form 8.8 to 9" on my 92 and that is all I had to do, I also however cut he perches off and welded on new (getting ride of lift block and wedge), so that might be a spot where you have a differance. If bronco to bronco axle should be fine. The shock mounts and everything where right on.
Now should you is completely different. I did it as so my bronco's would match and I have moved parts from my 78 to the 92 as I upgrade the 78. The 8.8 is good axle too though. I would get the tubes welded to the center when its out though.
 

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Discussion Starter #9
Hrm.. I'm not seeing Dana/Spicer gears there. The only ones I see are SVL, which say "backed by Dana". Those?

I think '89 was the first year for the flange yoke. My '85 8.8" is the same yoke as the 9".
And yes, the 9" is out of a Bronco, so the shock mounts and everything look to line up just the same. Again, the big perk being that I can disassemble and build the 9" and drive the Bronco at the same time. I guess I'll have to price rebuild kits, gears, truetrac, etc and see which one makes more economical sense. If it's the 8.8, then I'll just leave the Bronco down while I pull it, which isn't a big deal. But if it's the 9", then that'd be nice.

If anyone else has thoughts on ring/pinion manufacturers (even if they're different front and rear) I'd love to hear.

Thanks all.
 

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Discussion Starter #10
Can't the 8.8" be outfitted with disc brakes from an Explorer or something? If so, that'd be a perk for sure.
 

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Discussion Starter #11
Another thought with the 9". Isn't it pretty straightforward upgrading it to a 35 spline axle? Again, I've never been very worried about strength, but since I'd be rebuilding and purchasing all that stuff, might as well beef it up a little bit.
 

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Yes, some Explorer rear disc swaps have been done, sounds pretty easy and something I'm considering myself. BossInd has a write up from a while ago.
 

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1996 EB w/5.8 TOO much lift, 44" Mudders & 5:43-5:38's
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I'm a 9" fan, but I'm old, and they were the strongest rear available back in the day. I like the ability to be able to have different gear ratios set up in different housings, that can be swapped out quickly, although in 4WD it's a mute point.
There are no C clips on a 9" so the axles can't walk out on you. You can also buy C clip eliminator kits for a 8.8 also. Explorer disc kits are available for both the 9' & the 8.8, although I find the drum setup to work better.
I like Detroit lockers, I plow snow, have been since the 70's and I have run lockers since then also.
I run a Tru-Trac up front. Limited slips just plain suck; clutches are always wearing out, especially under hard use.
Gears are pretty much made everywheres but the good 'ol USA these days., even Ford Motosport. I have had good luck with Yukon lately.
You can get 31, 33 and 35 spline axles and carriers for 9" rears.
As far as gears, I probably would step up to 4:56 if your pushing snow, that and the fact that you will probably go up in tire size down the road.
If you are thinking of setup your own gears, check my build thread.
Either way, good luck.
 

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Did the upgrade from stock a few months ago.

33s, 4.10s, Ford Torsen in the rear, auto locker in the front.

This setup has increased off road, and on road, performance beyond what I expected.

Love driving this thing again!

 

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1989 Eddie Bauer 5.8, C6, True Trac diffs, 4.56 gears, 4" C&T lift, 130A 3G Alt, 35" Grabber AT2s
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SVL gears are made by Spicer Dana, that's what I have
 

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that was the set I was thinking of

If you go 35 spline or something different the stock, It is not a ton more money just to buy a 3rd member ready to go, with what ever diff and ratio you want. It is what I did. Also makes it super easy as no gear setup.
 

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1996 EB w/5.8 TOO much lift, 44" Mudders & 5:43-5:38's
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Dana is no longer made in the USA; I have friends that have bought them and it shows a different Country of origin.

From another site:
" OEM Dana:
Many believe that Dana Gears are all made in the USA but the fact is, they are made allover the world. Dana makes very few gears in the US any more, most are made in South America but they also use Some China and a couple other countries. The quality is top notch and almost always will set up using the factory shim that you take out.

SVL Dana:
Made in India, but the quality is good, but often the surface finish looks less than perfect but they will still setup well and run trouble free for years.

Yukon/Randy's Ring & Pinion
Yukon is a huge mix of gears made in all corners of the world. Early on, the quality was very up and down because they had no in house quality control and just filled the box with what ever they could get their hands on. That has drastically changed over the years and they now spend a lot of time and money making sure, if it come in a Yukon box it's worth a shit! They now have a whole department that only does "QA" on every product as it comes in the door.

USA Standard/ Randy's Ring & Pinion
This is Randy's "Economy" brand and is made up of a wide verity of gears. Very often the gears in a USA Standard box are the very same as what is in the Yukon box of the same part. The reason for this is because when you are buying 15,000 gear sets a month, it's no cheaper to buy a crappy gear than it is buy a good one so why create the headache of buying the same gear from multiple sources. The reason this brand exists to offer an option to bottom feeder customers that only car about price rather than quality or warranty. Randy's also fills this brand to sell off gears that don't quite make the grade for the Yukon brand, so you can't always be sure that it will be the same as what's in the Yukon box.

Revolution Gear
Revolution is a very consistent brand because they ONLY use gears made in Korea and Korean gears have always been known in the aftermarket as being high quality with rare exception. Because Revolution only uses Korean gears they have holes in the application and ratio offering but manage to offer most of the popular applications. They offer a select group of "2 Cut" Gears are super nice and are guaranteed to be quiet.

US Gear
USG has notoriously made good gears, the only real drawback with them is lack of depth, back orders and high price. But if you want a good gear and you have doubts or concerns with other brands, or if you just like to buy made in the USA, USG is the way to go.... if you can get them.

Motive Gear/Richmond Gear/Midwest Truck
This is by far the most complex gear brands out there. Motive Does "Red Box" "Blue Box" "Black Box" under the Motive brand. I cant speak to where all their gears come from but I do know that they come from all over the world. "Red Box" Gears is their top quality/High Performance line, "Blue Box" Is their more general purpose line and the "Black Box" is economy line. I have used all three and have found all to setup well and run quiet, including the "Black Box". Like Yukon they have a strong QA department that makes them very consistent.
Midwest Truck is the company that owns Motive and Richmond Gear. They bought Richmond back in late 2005 and killed the US made "Yellow Box" gears. They still offer the "Yellow Box" and the quality is still good, they just aren't made in the US anymore. I know they use a manufacturer out of Italy for a lot of them but I'm not sure where they are all coming from. In my experience it appears that the Yellow Box Richmond seem to be the same gears as the Red Box Motive but I have used enough to say that is an absolute.

AAM (American Axle Manufacturing)
Mostly the OEM supplier to GM and for Dodge 3/4 & 1 Ton truck axles, but also sell a lot into the aftermarket. Most AAM gears are made in India & South America but they do still have a very small number of gears made here in the US. Quality is always very good and price is reasonable on most of their stuff considering it's coming from an OEM supplier. They offer very little that fits the "Off Road" market.

Nitro
They are much like Yukon in the fact that they re-box a fair amount and buy from manufacturers in India, China and some Korea. They don't have the quality control that Yukon Or Motive but seem to have okay quality as far as I can tell.

G2
Fills their boxes with gears made mostly in Korea, but is very shallow in their offering focusing on mostly Jeep and late Model 4X4s.

The reality is that for 99.999% of the world the brand of the gear will make no difference and the failure rate is very similar across all the brands. 99% of gear failures and gears that have noise after setup are the fault of the mechanic. Most of the mechanics in the world have ZERO gear setup experience, just because you are good mechanic doesn't mean you should set up a gears."
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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Without reading all these posts, here's my thoughts.

The 9" is no stronger in stock form. Both the 9 and 8.8 can be built to be strong enough for 500+ HP with aftermarket parts. So the only real difference is if you want a removable 3rd member or an inspection cover. Since the 9 came from a bronco, it would be a direct swap.

As for the diffs, definitely go trutrac. Since you get ice, there is no better option besides an open diff. An open diff is always safest on ice, thats why the selectable lockers are nice. I do believe the Auburn Ected locker is an LS when unlocked... And you will love 4.10s with 32s. All my f250 and f350s have always run 33s and 4.10s. In a loaded down regular cab 95 f250, with a tired 460 and zf5, and 33s and 4.10s, I drove 15 hours to southern CO and back, averaging 14mpg.

Keep in mind that with taller gears that yes, your RPMs will be higher, but your engine will be working less, and you wont be in the throttle as much going up hills. My general experience with changing gears and tires is that mpgs dont suffer much if you have overdrive. My blue 94 had 37s and 4.88s. It got the same mpgs as 37s and 3.55s.
 

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Discussion Starter #19
Thanks for the feedback everyone. And @cobrajoe thanks for the writeup on the gears. That's helpful.
The only one that's not meshing for me is SVL. From what I've seen, they're the least expensive, and this is their writeup Broncograveyard:

SVL™ brand products are the smart choice for older (post warranty) vehicles, and those used seasonally or in lower mileage and light duty situations. When genuine original equipment performance specifications are either not required or exceed your budget constraints, SVL products keep your vehicle rolling while protecting your bottom line.
That doesn't give me the warm fuzzies.

That said, Summit Racing also now offers their own gears, and they all look to have about 4 - 5 stars on their site. They're also very reasonably priced. I know they've really been coming out with some good quality products. Most of which, I imagine, are reboxed versions of high quality stuff from other vendors. Dunno.

I think I'm sold on the 4.11s. It'll give me a really nice performance boost without getting too crazy. The RPMs on the freeway will be very similar to my '81 Bronco with the 3.00 diff and the NP-435 (no overdrive). At cruise, it had a 3.00 gear ratio (3.00 * 1.00). With the 4.11s and overdrive, I'll have an equivalent of a 3.12 (4.11 * 0.76).
I had thought about how with the higher gears, it won't be working as hard. I think it'll be a really good compromise and balance. I also have zero intentions of going with larger tires in the future. For what I do, it's just right how it is.

As for the TrueTracs, that's why I like the idea of them. They don't have clutches that wear out, and seems like they'll give good driving manners year round.

On the 9" vs 8.8". No, I really don't care that the 9" has a removable 3rd member. Cool, but it's not something I'd ever do. But being able to set it up with a 35 spline vs a 31 is appealing, however. Does the 8.8" have something similar?
 

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Discussion Starter #20
The more I read, 35 spline seems like total overkill for anything I'd do. But, it's only like $200 more to convert the 9" over. Any downsides to going up to a 35 spline vs. a 31?
 
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