Diagnosing broken front axle (1 Viewer)

[Project80]

Hi everyone. I'm not an 80 series owner yet but I'm looking for a project car and thought an 80 would be a great project. I came across a 1997 40th anniversary edition one listed relativity cheap because the owner says it has a broken front differential. From what I've read here it's much more likely that the problem is with the birfields.

What steps can I take to diagnose the problem before buying the vehicle and determine whether it's a birfield, differential, transfer case or something else completely?

What is the likelihood that it is in fact the differential? The transfer case? How expensive or difficult are these potential issues to fix in my driveway? I've seen several videos on replacing the birfields and it seems easy enough. A transfer case or differential look more difficult though.

 

[greentruck]

SNIP

What is the likelihood that it is in fact the differential? The transfer case? How expensive or difficult are these potential issues to fix in my driveway? I've seen several videos on replacing the birfields and it seems easy enough. A transfer case or differential look more difficult though.

Very unlikely to be the transfer case.

As for diff or birf, does the truck run? That's likely to give you the best indication, if nothing else the noise made (if any) will either be centered (diff) or outboard (birf.) If you drain the front diff and find lots of metal, that's a pretty good sign, but just a little metal would be indeterminate. The birfs typically click when starting to go bad, but if the problem parked it, then something worse was likely going on.

Yes, doing the birfs is just part of servicing the front axle, so no big deal to replace. People often swap birfs side to side to get some extra miles by evening out the wear.

Diffs are a bit deeper water. You can get the whole thing set up and a good wrench can then do it in the driveway without too many special tools, but it's not a beginner's path. Setting the diff up itself requires specials skills and tools.

The 80's front diff is not so robust as the rear and has been known to fail when pushed. That said, it could be a birf that dynamited. Hard to say until you've peeled things apart. But whatever it is, it's not insurmountable at all with help from folks here.

 

[-Spike-]

Buy it assuming it's the diff, which is the worst-case scenario, if it's a good deal. If it turns out to be something else (and it likely will), then you are ahead. If not, you haven't lost anything.

 

[Corbet]

Might just be a drive flange. If the truck is stock hard to believe the front diff busted.

 

[flintknapper]

Might just be a drive flange. If the truck is stock hard to believe the front diff busted.

This is what I would suspect as well. Next...a birf.

Almost certainly not the Tcase, but if so....just replace with a used unit. They are readily available for not too much money.

 

[Kernal]

As mentioned above, it would help to know what the symptoms are when driven.

 

[Project80]

Appreciate the responses guys

I wish I could tell you the symptoms when driven but I haven't driven it yet. The owner says everything is fine except it makes a loud noise in the front when driving. I was more wondering what the symptoms are of a broken diff vs. bad birfs so I can figure out what the problem actually is when I go to look at it. For example if I lock the center diff should I expect a different sound if it's a broken diff? Would taking a jack with me and trying to spin one of the wheels tell me anything?

I'm hoping it's a situation where it would've cost the owner a lot to pay a mechanic to fix a broken diff so they decided to sell instead. It's listed at $5500 right now but I'm almost certain the owner will sell for under $5000 because it's been listed for a while. Does that's seem like a good deal for to you guys? It seems like way more than people would've paid two years ago but seems worth it to me for what they're going for these days. I think as long as it doesn't need a new engine or transmission it's going to be worth it.

The only other one in my area around the same price was a 91 which seems to be not be worth quite as much because of the weaker engine. That one was a blast to drive but unfortunately it was from up north and had a bit more rust in the engine bay than I was comfortable with even though the undercarriage looked good. I think it would require removing the engine and transmission to fix that rust and it's just not something I'm going to do realistically and would probably seriously limit the resale value. It also had a coolant leak and a lot of small cosmetic stuff but none of that was a huge deal to me other than the rust.

 

[flintknapper]

You just need to drive it and see if you can isolate the noise to a specific area.

You could drop the front driveshaft, jack the vehicle up and turn the wheels by hand to see IF it would point to a certain area in the front axle, but most folks selling are not going to let you do that. It could be any number of things. We are just speculating without more info.

 

[Dave 2000]

Whilst I agree with @greentruck it is unlikely to be the transfer, a few have come to my attention over the last couple of years, indeed one on my own 80. The symptoms are virtually zero or zero drive in any direction, regardless of Hi/Lo T case lever or transmission lever position. The sound is of cogs grating but it is difficult to pinpoint position despite the T case being towards the rear of the vehicle. If the car moves when in low (centre differential now locked) then I would be looking at the front axle.

A broken Birf is a distinct possibility but the noise would come up over time, it is rare in the normal course of driving that they fail with no warning. A differential the front in particular will fail without warning if the owner was perhaps pulling something in reverse? There is a large bang and no drive (or very little if a Viscous Coupling is fitted and working, query the seller a little bit more to find out how, what and when the car failed.

regards

Dave

 

[MUDZLLA]

FWIW I've had birfs fail suddenly if the front diff is locked and you are turning too tightly or on hard ground - even gravel. The bearing cage snaps suddenly. Sound like rocks in the knuckle and have to lock center diff to move.

Broken ring/pinion will start as intermittent grinding as the broken teeth come around.

 

[slacker83]

My vehicle had the birf and drive flange stripped so the birf was just spinning inside the drive flange. Wouldn't move unless the center diff was locked, because all the power was being sent to the wheel with the stripped drive flange and birf.

 

[MUDZLLA]

My vehicle had the birf and drive flange stripped so the birf was just spinning inside the drive flange. Wouldn't move unless the center diff was locked, because all the power was being sent to the wheel with the stripped drive flange and birf.

Same but only slipped intermittently for like 1/2 a second then would be fine for a day or two. Finally started slipping more frequently and longer periods before I changed birfs and flanges. Should have paid attention to IH8MUD and got the longer outboard spline setup of the 95+ models.

 

[Project80]

Would it be somewhat safe to say that if it's a clicking sound from either side it's probably a birf and if it's more of a grinding sound from the middle it's probably the diff? The seller just said "loud sound" but I'll try to inquire further. If I'm pretty sure it's a birf I'll probably just get it as long as it doesn't have any other major issues. Even if it ends up being the diff that wouldn't be a big deal as long as it's priced appropriately.

If it ends up being the diff how much can I expect to spend on a used diff vs a rebuild vs an aftermarket one and which would you recommend?

 

[Corbet]

Click = birfield

And if it drives with transfer case in high range very unlikely the front end has a total failure. With the AWD system a broken front diff or driveflange would leave you dead in the water. Failing front diff would be noisey same for failing Driveflange.

Used front diff probably $100 from salvage as long as not locked. Flanges are pretty inexpensive but are generally replaced with birfs so that splines match cleanly.

 

[Project80]

Yeah seems to me there would be no movement if the front diff is broken and the center is unlocked. If it's driving in 4 high I think it's probably not the differential. I'll definitely try it with the center both locked and unlocked to see if there's any difference.

 

[Kernal]

The 95 FZJ80 I picked up a few months ago had a frozen viscous coupler (unknown to the owner). The owner/seller said his mechanic had removed the front driveshaft because the noises (clicking and chirping of tires when turning) were from the CV joints that were going bad. But it wasn't the CV joints (Birfields) that were going bad, it was from the binding of the drivetrain from the frozen viscous coupler. Just one more possibility to consider. FWIW.

 

[jpoole]

It could be a few things but I'm with @Kernal possible hunch above. The '97 that I bought also had a frozen center diff which I assume had made a mess of some of the front axle components because when I bought it the front inner shafts and birfs were missing. When I finally got it all back together the front diff was worn out and had a decent wine so got replaced also.

If the 80 isn't rusty and is in good shape otherwise I wouldn't worry that much about needing to piece together and regear the front-axle, just make sure that the purchase price and your schedule leaves room to repair/replace as needed.

 

[ppc]

It could be as simple as a mostly failed universal joint on the front driveshaft.