Front diff or cv failure in the bush

[MalcomM Senior Member Find all posts View Profile Close MalcomM]

Hi guys

Just destroyed my 100 series front diff at Turon so thought I should brush up my knowledge on cv replacement in my 90.

What do you do if, like me, you do not have a spare cv in the truck?
In the 100 I have removed drive flange plates which connect the cv axle splines to the wheel hubs, drop the front drive shaft and lock the centre transmission effectively making it 2 wheel drive but you can't do that on the 90.
It appears to me that you would have to remove the entire broken axle, or if you are lucky just the snapped off hub end.
If you remove the axle(s) then you are going to loose the diff oil and water/mud entry may be a problem. Rags will only stop so much.

So, what do you guys do in this situation. Anything clever or am I correct and you are basically stuffed?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Hey mate,

I've had around 6 CV failures and 5 of which did not snap entirely, so was able to continue driving without affecting driving ability. Of course the joint failures held me back from pushing the rig through very extreme stuff, but I've often had no choice but to continue through hard tracks such as wheeny creek and spanish steps with a failed CV joint (and made it out every time).

The single time I had an entire shaft snap, was lucky in that the snap occurred near on the outer joint. All that was required was to undo the inner boot, and slide the mid shaft from the tripod cup (VERY easy). Leaving the inner shaft in the diff means no oil loss, and the outer shaft/joint remained in the hub. No issues driving home. I've also been witness to a CV snap on a Hilux - it also snapped at the outer joint so we performed the exact same process.

However, if you really want to be prepared for a complete inner joint failure (or inner shaft failure), then you'll need some way to deal with a dangling mid shaft. I believe we cannot remove the entire axle and drive home as I read online the outer shaft/nut may have some role in holding the hub/bearings together. It would be great if this could be confirmed, but I'm not likely to test it out myself given the risks. Assuming this is the case, the next options are to either bring a spare outer shaft only, a spare entire CV, or learn how to pop a mid shaft from an outer joint (and practice/prepare for it, cause it's not easy).

[MalcomM Senior Member Find all posts View Profile Close MalcomM]

Thanks Glenn

I hadn't considered that the wheel hub will fall apart without the CV and its retaining nut. Rather obvious now that you've pointed it out.

With the shaft snapped and leaving the inner axle in the diff, I assume you have a front locker or have removed the front drive shaft as the diff should transfer all drive to freely spinning shaft?

With a snapped inner join,t I guess some fencing wire could be utilised to hold the middle shaft up a bit so it doesn't flog itself against the rest of the suspension?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

You're correct an open diff will send all power to the freely spinning inner axle, the solution is to keep the transfer locked. All driving force will be sent to the rear wheels in this case, whilst the front diff & freely spinning axle will absorb the differences at the front. A front locker could be used as an alternative (with transfer set to open), but with the risk of it disengaging unexpectedly if air pressure is lost - and driving force will come to a halt.

I think the wire option might be useful for traveling a very short distance at a very slow speed - to find a better place to perform repairs. Anything at speed or long distance would be risky, the vibrations likely significant. Ensuring it can hold the weight whilst not hitting anything during suspension extension/compression will be the challenge, as well as not hit the inner axle (so remove the inner cup). Your idea makes me think of creating a bracket from steel which could be bolted in place for this task - but why not just bring a spare outer shaft or full replacement shaft?

The way I've been dealing with this is to bring an entire CV axle on hardcore trips only (rock crawling where I'm expecting to use both lockers). I don't take a spare for camping or mild 4wding (which includes mud, sand, ruts, mild rocks, high country, etc). Thus far I've never had to change an axle in the bush, thus, no reason to bother sourcing an outer shaft to speed up the process.

[pjorek Advanced Member Find all posts View Profile Close pjorek]

Reading the above, so it would be possible to drive back with the front locker engaged (in my case electric) and transfer case unlocked?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Reading the above, so it would be possible to drive back with the front locker engaged (in my case electric) and transfer case unlocked?

On a 90 series yes - but only in the failure scenario where a mid shaft has been removed, resulting in one of the inner-shafts spinning freely in the air. This is because one of the front wheels is not connected to the drivetrain. Driveline wind up won't occur whilst the transfer case is left open, as the transfer is designed to allow a difference between front and rear axles.

Actually, this is just my technical understanding of how it'll work - I never tried this method - I've always preferred to keep the transfer locked, front diff unlocked, and allow the front diffs spider/side gears to absorb any differences. You could even remove the front prop shaft if you're concerned - but it's unnecessary.

Note the 120 and 150 series have a difference in their transfer case - they have some kind of torsion/clutch system to manage excessive tyre spin when in HL. For those, I'd definitely lock the transfer and keep the front diff open.

[MalcomM Senior Member Find all posts View Profile Close MalcomM]

Definitely lock the transfer and keep the diff open. The less spinning problem parts the better.
I'd likely also be dropping the front drive shaft just to be sure there's less parts that can be powered to destruction.