Axle truss?

[krisbassett]

Since I have the 8.8" rear all torn down and being rebuild before going into my Bronco I figured why not put a truss on it. So.....What do you guys recomend?

 

[broncnaz]

Not really a common axle for us here. From what I've seen most of the braces availible for the 8.8 appear to cut down ground clearance. Not sure if I'd really bother with bracing a 8.8. Maybe just fully weld the axle tubes at most.

 

[Broncobowsher]

Personally I would recomend a 9" for an early Bronco...

What makes you think you need a truss? If you are planning on putting so much power through the axle that you need a truss, then 8.8 is the wrong axle to be starting with.

 

[krisbassett]

8.8" has a higher load rating than the 9" and it's not a matter of need so much as a matter of I would like to build the axle to it's highest potential before I send it home.

 

[broncnaz]

Thats a minimal load rating differance and probably most of its only due to the 31 spline shafts the 8.8 comes with. Add 31 spline axles to a bronco 9in and its about 30% stronger than it was. Also some of the 8.8 axles were only rated at 2750 lbs
Overall I would say the 9in is a much better axle and can be made much stronger than the 8.8 with a few upgrades where theres little in the way of upgrades for a 8.8. Got to also keep in mind the 9in design was in production for about 30 years and is still sought after today where the 8.8 has been around about 20 and was only used in larger trucks for about 10 before they went to a even bigger axles. Ever wonder why? Because that 8.8 is just not the axle its cracked up to be. Its fine for Mustangs Rangers and explorers. that really dont need the weight capacity.
Not saying that the 8.8 is a bad axle but its just not really all that great when it comes down to it. I realy dont think its better than a 9in in any sense.

 

[Apogee]

I'd weld the tubes and call it good unless you plan on jumping the thing, in which case I'd consider trussing it over the top so as not to limit your ground clearance. You can't really truss the rear like a 9" due to the cover.

 

[krisbassett]

Thanks for the replies. I know everyone likes the 9" more.......but I'm going with the 8.8". I was also wondering if it would be possible to build a truss that goes over the rear but is bolted so it can be removed if needed?

We have a couple tough truck competitions around this area and I may enter once I get all my suspention setup so there may be a jump or two involved LOL

 

[broncnaz]

Anything is possible I'd be a little concerned with frame to axle clearances with a top mounted truss, not to mention a bolt on type deal is not really going to add much in strenght. Might want to research what all is availible for the 8.8 might give you ideas or a source for a premade item.

Most people consider the 8.8 a down grade when replacing a 9in. The only time the 8.8 is really a upgreade is when your talking about jeep axles. 2 common weak spots on the 8.8 is the gears are not as strong and the axle tubes can twist.

 

[DirtDonk]

I think we can stop trying to talk Kris into a 9" by now. In the last three threads it's been beat to death.
So, concentrating on the truss aspects, what they're saying about some types of trusses kris, is that the bar type (or any that runs underneath) is going to lose you some ground clearance and that's not a reasonable trade-off for most. So if clearance is a possible issue (it usually is) then consider something that welds to the top of the diff.
In the case of the 9", we can add one to the rear that stays cleanly out of the way of most things, but your 8.8 has a removable cover, so that has to be taken into account if you try to use/design something that welds to the rear face.

Personally, I think trusses are a great idea. Skid plates too. If it's easy to work one into the build, why not? But if either one tends to get in the way of something else, loses too much ground clearance, or is otherwise a problem to mount in a particular combination, the trusses and skidplates are usually put to the end of the list nowadays.

Used to be some of the first things added, but are now typically used only in desert racing, dune-running, or heavy load carrying circles. Wherever excessive deflection is going to be an issue. Typical rock-crawlers or casual wheelers don't usually over-tax their differentials in such a way as a truss would help more than hinder.
And even then, the front tends to get more attention since the long-side tube is usually the first to go on a dune-runner or rock-hopper with big tires and big drops. The longer front tube can be more prone to flex than the stronger, shorter, equal-length rears and short side fronts. At least it used to be that way years ago. Things and needs change, but it still seems possible.

If you're going to be doing fast firetrails, jumping sand dunes, or loading firewood regularly into the back of a truck, or running uber-large tires in those situations though, and don't mind the clearance trade-off factor, it might pay off.

Hasn't been discussed much recently though, it seems, so not as much first-hand experience here as with other things-Bronco.

My 2 cents.

Paul

 

[krisbassett]

The axle tubes are going to be welded to the center section. The gears seem to be pretty stout. They are every bit as beefy as the gears in my 9" rear. The only thing I can se that I'm loosing is the ability to change the 3rd member quickly which would not happen in my case anyway because I have no extra 3rd member. I know there are mustang guys running 8.8's in 1000HP cars. That's way more than I'll be putting to it and track runs with wide sticky tires are hard on rear ends.

 

[DirtDonk]

Have you looked at Duff's and Jeff's sites lately? Duff used to sell things for the 8.8 diffs, and Jeff's caters to more than just the EB's, so might have more choices (if they exist) for the 8.8 too.

Good luck.

Paul

 

[krisbassett]

I think we can stop trying to talk Kris into a 9" by now. In the last three threads it's been beat to death.
So, concentrating on the truss aspects, what they're saying about some types of trusses kris, is that the bar type (or any that runs underneath) is going to lose you some ground clearance and that's not a reasonable trade-off for most. So if clearance is a possible issue (it usually is) then consider something that welds to the top of the diff.
In the case of the 9", we can add one to the rear that stays cleanly out of the way of most things, but your 8.8 has a removable cover, so that has to be taken into account if you try to use/design something that welds to the rear face.

Personally, I think trusses are a great idea. Skid plates too. If it's easy to work one into the build, why not? But if either one tends to get in the way of something else, loses too much ground clearance, or is otherwise a problem to mount in a particular combination, the trusses and skidplates are usually put to the end of the list nowadays.

Used to be some of the first things added, but are now typically used only in desert racing, dune-running, or heavy load carrying circles. Wherever excessive deflection is going to be an issue. Typical rock-crawlers or casual wheelers don't usually over-tax their differentials in such a way as a truss would help more than hinder.
And even then, the front tends to get more attention since the long-side tube is usually the first to go on a dune-runner or rock-hopper with big tires and big drops. The longer front tube can be more prone to flex than the stronger, shorter, equal-length rears and short side fronts. At least it used to be that way years ago. Things and needs change, but it still seems possible.

If you're going to be doing fast firetrails, jumping sand dunes, or loading firewood regularly into the back of a truck, or running uber-large tires in those situations though, and don't mind the clearance trade-off factor, it might pay off.

Hasn't been discussed much recently though, it seems, so not as much first-hand experience here as with other things-Bronco.

My 2 cents.

Paul

Thank you very much!! This will be used as a hunting rig so it will be pulling a fairly big heavy wheeler trailer quite a bit and it may see a couple tough truck competitions and whenever I'm Elk hunting and get something down while I'm in the bronco it will be loaded in the back. I just figured why not as long as it's out and on the ground. I'll have to do some measuring and see what clearances I have. I assume it could be welded on the front side aswell?

 

[DirtDonk]

It's not only the easy-change aspect that makes a difference though. It's that nice little additional bearing that supports the end of the pinion that is one of the main things that sets the 9" apart from most other diffs. That one design characteristic alone adds a lot to the relative reliability under stress of that axle. The only other common one I can think of that has one is the GM 10.5" corporate 14-bolt diff. Ultra-beef there!

I wouldn't think that a trailer that would normally be compatible with an EB would be too much for an axle like yours, but I guess that depends on what your idea of "Bronco-compatible-trailer" really means! Even a monster elk shouldn't be too much, unless you're going great distances on the highway, or like to keep your speed up over whoop-de-doos when coming back to camp.
The Tough Truck Challenges though? Now THAT's a whole nutha thing! I'd say for that alone, you'd want to truss both axles with something very strong and as light a design as you can think up.
Say no more...

I don't see anything completely out of the realm of reasonableness by putting one on the front. Just have a lot more things to tak into account when fabbing up the form to fit around the shapes of the casting.
And you'd most definitely have to have the thing completely disassembled and jigged up so you won't melt any seals, and reduce the chance of warping the housing. I suppose you could avoid any "jigging" hassles, if you do short stitch-welding moving back and forth far away from the previous stitch.
But I'm no welder, so the others would have better opinions on the best technique to use.
For a bolt-on setup, I think you're limited to top or bottom, with the bottom being the simplest to design, but the top being the best of both worlds. Assuming you can make the bolting method flex-free and solid.

And take pictures! We want to see it, and if you're on any other forums (like Rangers and Pickups) they'd probably want to see what you come up with too.

Paul

 

[krisbassett]

When my 9" gave out on me 2 years ago it was because the housing cracked out where the carrier bearing is. I was trying to find a nodular 3rd but ended up geting what i could. I also rebuilt the stock limited slip one of the spider gears ate the chunk of iron that broke off. I was able to mod a spider from an open carrier and get mine back together. I cut the collared part of the gear off and it matched the limited slip gear perfect!

But anyway I think I'm going to visit with a structural engineer here at work and see what my options will be for best strength,

 

[DirtDonk]

Great! Let us know what he/she says about it. Maybe they can even sketch something up on CAD that you can have cut out and ready-to-weld in no time.

Paul

 

[ken75ranger]

Weld the tubes, get a diff. cover that preloads the bearing caps and run that thing! The 8.8 tubes are thick enough to handle a moderate beating.

 

[krisbassett]

Weld the tubes, get a diff. cover that preloads the bearing caps and run that thing! The 8.8 tubes are thick enough to handle a moderate beating.

Where would I find a cover like that?

Thanks
Kris

 

[Steve83]

The thicker axle tubes & cast center make a truss unnecessary for an 8.8 . Welding the tubes is enough.

The bearing caps preload the carrier bearings, so that's not really an issue, either. If you want to upgrade the cover (which I recommend), get either an aftermarket heavy steel cover, or the stock IRS cast Al cover.

 

[krisbassett]

Ok fellas I guess I will just weld it up put the heavy cover on and see what happens!! Thanks for the help!

Kris

 

[DirtDonk]

I think Ford Racing used to sell a cover like that, but there are probably several companies that do by now I would think.
Funny timing, but just in this month's Four Wheeler mag, the "Willie's Workbench" segment talks about doing a skid-plate on an 8.8.
Naturally, they don't go into any detailed descriptions. Just that it's a useful thing to do for low-hanging diffs.

Paul