Trussing a FORD 8.8?

Ok, i have had an 8.8 with 3.73 and trac lok for a few years since my days of wanting to swap it into my custom ranger, well i still have it so i'm going to throw it in my xj. But i have a few questions.

1st: I requested a build seet for my xj which states i have 3.08's, i know 8.8 3.08 gears are a dime a dozen. I drive a lot on street mind you this is my winter/rain/kindof daily driver when i don't want my contour svt out. So my question is... should i get 3.08's for the 8.8, don't really want to lower my ratio much since i get 17mpg. or should i get some gearing that meets in the middle (between 3.08 and 3.73)

2nd: Trussing a 8.8? anyone does it? I like the aesthetics aspects of it and figure while i'm welding on perches it wouldn't be too much of a pain. Trussing in general: i've heard welding on cast weakens it incredible bad and theres some process of preheating the metal... would tig be best? or is mig suitable? next... would it improve the 8.8's strength at all or is it good enough?

3rd: Is the kit worth it from whatever copany it is for the 8.8 swap to an xj? i know it comes with axle perches(can get for about 13$ from local dirt track shops) shock mounts (sure they can be made or had locally) and a u joint converted piece... so is it worth it?

If it's just a street vehicle and you want to keep the highway gearing why are you dropping the 8.8 in?
Leave it, drive it.

Anyway, trussing an 8.8 is pretty straightforward, just like any axle. Welding cast steel isn't a problem, just preheat it before welding. Mig will work fine. Again, why though?
If you're not planning on lifting it (I assume not) then no one will see it so there's not much point to the aesthetics issue.

kid4lyf said:

Anyway, trussing an 8.8 is pretty straightforward, just like any axle. Welding cast steel isn't a problem, just preheat it before welding. Mig will work fine.

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Good thing it's cast iron for the center section. If you try and weld something with a MIG to that, I guarantee you I'll give it two hits with a 3-lb sledge before it chips off. You really need to use high-nickel-content welding rod and an arc welder to do it right. Preheat the whole joint until it'll easily melt a wax crayon. Lay the weld in small increments (and have a cool, wet rag placed over the axle tube ~6" away to help prevent tube warpage). You will also need to post-heat and stress-relieve the weld after laying it, by heating it with a torch occasioally as it cools down, and also peening the weld with a small hammer. If done right, you won't weaken the cast iron at all.

It's a weekend warrior but i still drive it a lot on the streets and would like to keep my mpg. And i think my 4lo is low enough. But my rear axle is junk... always either spin no tires or maybe one.

It's lifted 3"s now, and i have a 8.8 that i couldn't sell, so i'm just gonna toss it in. I have 31's also. My future intails a couple more inches in left and 31"s or 32"s, just wider.

vetteboy said:

Good thing it's cast iron for the center section. If you try and weld something with a MIG to that, I guarantee you I'll give it two hits with a 3-lb sledge before it chips off.

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I do believe it's cast steel.
It's pretty easy to tell as you're welding to it. Especially with MIG which is what I used on mine.
It's rare (not to mention, terrible engineering) to use cast iron in an application where it has to be welded.

vetteboy said:

Good thing it's cast iron for the center section. If you try and weld something with a MIG to that, I guarantee you I'll give it two hits with a 3-lb sledge before it chips off. You really need to use high-nickel-content welding rod and an arc welder to do it right. Preheat the whole joint until it'll easily melt a wax crayon. Lay the weld in small increments (and have a cool, wet rag placed over the axle tube ~6" away to help prevent tube warpage). You will also need to post-heat and stress-relieve the weld after laying it, by heating it with a torch occasioally as it cools down, and also peening the weld with a small hammer. If done right, you won't weaken the cast iron at all.

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I've welded to cast a bunch, including trussing my 8.8. Pre-heat, MIG, post heat, and slow cool. Never had a problem, but I did use some high-nickel rod the other day, and I have to admit that I think it penetrates better and is not as brittle. I'll likely keep my other methods the same, and switch to nickel rod for my cast work now.

Vetteboy is both wrong and right.

It is cast STEEL not iron. Steel is defined by the carbon content. It is a pretty common, although incorrect, misnomer to call the pumpkins and knuckles "cast iron". They are all cast steel.

He is right in that the 'best' way is to weld it is with a high nickle rod. However, it is not the only way. Pre-heating and MIGing or 7018 rod is also fine and very, very common.
Failing to properly pre-heat can very likely lead to the kind of weld failure he mentioned.

I would assume he is speaking from experience there..... as I know everyone else in this thread is.

C-ROK said:

Vetteboy is both wrong and right.

It is cast STEEL not iron. Steel is defined by the carbon content. It is a pretty common, although incorrect, misnomer to call the pumpkins and knuckles "cast iron". They are all cast steel.

He is right in that the 'best' way is to weld it is with a high nickle rod. However, it is not the only way. Pre-heating and MIGing or 7018 rod is also fine and very, very common.
Failing to properly pre-heat can very likely lead to the kind of weld failure he mentioned.

I would assume he is speaking from experience there..... as I know everyone else in this thread is.

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Yeah, definitely done this before. I did it in a welding class at school as an extra project. I brought the axle in and the instructor had me just lay a bead with the MIG on one of the flat gussets on the housing, setting it up for proper penetration with .035" wire. Laid a nice straight bead that woulda stuck to any regular steel plate. He came by with a cold chisel, and with one hit with a small sledge, chipped the whole weld right off the housing. Very granular under the bead, typical of cast pieces. We then put a piece of regular A36 hot-rolled plate next to the housing, and went at both with a grinding wheel, and the housing made the distinctive spark pattern of a cast piece as compared to the A36. As a further exercise, he had me weld a small 1"x3"x1/4" piece of regular rolled steel to a flange on the housing using the MIG, which was promptly removed with a sledge. Pulled the whole weld off the housing leaving a small crater, again granular under the bead.

It's experiences like that (and a few more, that I did on my own with random cast pieces), that dissuade me from using a MIG on anything cast, or recommending it, be it cast steel or iron. In that same instruction session he referred to the housing as cast iron, which I've seen in many other places, but you may be right. I'll look into that more. I've generally thought that cast steel was more receptive to MIG welding than cast iron, and my prior experience there also leaned me towards the cast iron thing.

I mean, chances of spinning the tubes in an 8.8 housing are slim to none anyway - I don't know a single person personally who has done it, although everyone is quick to point out that it's a weak point on the axle. The fact that people have MIG'd the tubes to the housing and not had them spin is usually something they'll say to prove that yes, you can MIG to the housing and have it work...but I wouldn't give the welding too much credit. With enough surface area under the weld, it might hold up to something.

Bottom line is though, it's not the 'right' way to do it. The right way is with an arc machine and Ni-55 rod.

thanks guys! so preheat/ post heat and with high nickle

And my other questions? The kit? The gears?

vetteboy said:

Bottom line is though, it's not the 'right' way to do it. The right way is with an arc machine and Ni-55 rod.

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Wrong...

Sometimes the "right" way to do something is to get the job done with the materials at hand and have it do what you want it to do.


Real life isn't always a mcmaster carr or grainger catalog with a business account.

Gil BullyKatz said:

Wrong...

Sometimes the "right" way to do something is to get the job done with the materials at hand and have it do what you want it to do.


Real life isn't always a mcmaster carr or grainger catalog with a business account.

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Bullshit.

MMC and little g are for the havenots.

--ron

Gil BullyKatz said:

Wrong...

Sometimes the "right" way to do something is to get the job done with the materials at hand and have it do what you want it to do.


Real life isn't always a mcmaster carr or grainger catalog with a business account.

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That's great. I've never ordered anything but bolts from McMaster, and I've never ordered anything from Grainger. And I don't have a business account with either place, because I only work as a general contractor with a residential construction company and we don't need their stuff.

Again, you're confusing the 'right way' with something that 'apparently works'. If it works for you, great. If it works to the absolute potential of the material, the weldment, and the task at hand, then it's the right way. There is a difference.

so are there any people with 31"s and an 8.8 that suggest a gear for me? ( go threw some pretty good stuff but i think my 4lo in about perfect

waubm said:

so are there any people with 31"s and an 8.8 that suggest a gear for me? ( go threw some pretty good stuff but i think my 4lo in about perfect

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whatever your current gear ratio is so you dont have to re-gear the front diff...

If you already have it lifted and are running 31s I would swap in the 8.8 and put 3.73s in both pumpkins. With a manual (assumed since I have only seen 3.08s come in 5 speed 4.0L XJs) and 31s, the 3.73 will be perfect for street driving including highway. I ran 3.73s for a few months with my 32s before I could afford to regear the axles to match and it was fine.

I have my F8.8 trussed with a tube from both sides going over the top of the diff and a rock ring from Poison Spyder Customs rock ring with a link mount that connects to the truss/tube. I have pics but having issues with hosting them at the current moment.

AARON

could you send pics to [email protected]

also how will my mpg be effected? negatively or about the same?

A truss doesn't have to weld to the center section of the diff if it's designed correctly.

They're easy to fab but difficult to make look any good if you ask me. I've done a few of the tube-type trusses and they always just turn out ok.

If you're interested there is one that's weld-on which is now available from T&T Customs.



More info including price located here:

http://www.tntcustoms.com/webV3/88truss.asp

vetteboy said:

I mean, chances of spinning the tubes in an 8.8 housing are slim to none anyway - I don't know a single person personally who has done it, although everyone is quick to point out that it's a weak point on the axle.

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Wow, I wish I would have read this before I spun the tubes for the second time.........

CRASH said:

Wow, I wish I would have read this before I spun the tubes for the second time.........

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Really?

Crap, well there ya go. I figured there had to be a reason that people kept saying it happens. I just meant that I've never actually met someone who experienced it.

Yeah, but CRASH is an animal. A whole vehicle never lasts him more than a few years.