Upgrading rear driveshaft

[2TimingTom]

Yesterday I broke my rear driveshaft yoke:

I'm SAS'd with 4.56 gears and a manual transfer case. I've also been told that I need a longer driveshaft- I was told that when it was put on a lift at the shop the rear drops out far enough to pull the driveshaft apart.

Is the yoke from a V8 any stronger? Or is this failure pretty unheard of?

What about a SYE?

 

[Brian1]

From your description and the picture it seems to me that you were drooped out and torque was applied cracking the female slip yoke since there was minimal engagement right on the weakest part where it is machined for the boot.

If that is OEM Ford it will be a 1330 series most likely. v8 wouldn't be any different from the same application (Explorer). You could upgrade to a 1350 or 1410 series but that is not what broke. You need to address the slip in your driveshaft by measuring the compressed and drooped length between your yokes and give that to a reputable driveshaft shop that has experience with off-road to build a new one.

SYE does not apply. Your t-case already uses a fixed yoke.

 

[2TimingTom]

From your description and the picture it seems to me that you were drooped out and torque was applied cracking the female slip yoke since there was minimal engagement right on the weakest part where it is machined for the boot.

When it broke, I wasn't drooped out. But there have been many times that I have. When it broke, I was going up a snowy trail. The snow was probably 4-6" deep and I was probably getting wheel spin just to keep it moving as I was breaking trail. But otherwise it was fairly neutral suspension travel. My guess was the crack had been there for awhile and it finally gave it up.

SYE does not apply. Your t-case already uses a fixed yoke.

Yeah, I read into what a SYE is after I posted this. I don't know too much about driveshafts to begin with and with the aftermarket dominated by Jeep, I'm a victim of marketing. At least that's my story.

Would a driveshaft company be able to extend the yoke? Where do you make up for the increase in the driveshaft slip?

There's a driveshaft company in town here that is owned by a 4wheeler. They are closed on the weekend so I haven't been able to talk to them yet.

 

[Brian1]

This can give you a good idea: http://www.4xshaft.com/travel.asp

Your best bet is to see how much slip you need first by measuring. You may be able to still use the normal slip length and just get a longer driveshaft instead which would be cheaper.

 

[2TimingTom]

Stopped by the local driveshaft place tonight. He's going to build me a bombproof axle. I'm going from 32 spline to 16 so the splined sleeve will be thicker. The rear u joint will be a 1 ton unit. The tube itself will get bigger and thicker. It'll get more travel. It'll be awesome!

He thinks the reason it broke was because I was getting axle wrap while I was climbing the snowy section of trail. That rotated the axle downwards and thus pulled the driveshaft out toward the skinny part of the splined sleeve where just a little bit of the splines were engaged which basically caused the shaft to buckle by cracking the splined sleeve.

I'll post pics.

 

[2TimingTom]

Got my driveshaft but haven't been able to install it yet.

This is set at the static length- as it would sit on flat ground:

The dust boot on the stock shaft covered up the exposed splines but you can see how little of them are engaged.

I'm assuming this is about as fully extended as I would get while 4wheeling (with the stock shaft). I'm assuming the dust cap is hitting the splines on the new shaft.

3" tube vs 2.5" tube. 1330 and 1350 Spicer U-Joints. Greasable spline shaft and u-joints. The new splines are Teflon coated for better movement. 16 spline (new shaft) vs 32.

I asked him about the spline count. Typically more splines are better as it allows for more points of contact. He agreed. But when splines need to also slide in and out of each other, more splines leads to the potential of binding up those splines and then something else will need to make that movement (buckle the driveshaft, break an engine/transmission mount, over stress a bearing........)

But while on the trail, I dropped one of the bolts that holds the driveshaft to the diff. It's lost in the snow. Napa doesn't have them. Guess I'll be heading to the junkyard tomorrow before it snows.

 

[D.R.Ball]

Take one of the bolts to NAPA and check the Dorman bolt center, no need to go to a junk yard. The bolt should be a metric bolt by the way. No NAPA nor any parts store will know what size or part number for each make model or year but should have the bolt size that you need. Or any good local hardware store....If it's a grade 8 bolt make sure you use the same grade bolt.

 

[2TimingTom]

I did. He looked. No dice. Maybe I'll look online tonight and try a different store.

 

[D.R.Ball]

What it's look like. If it's a normal bolt than you need a new parts guy. Do you have a thread pitch gauge , if not take the bolt to Home Depot etc. and try to match it your self. They have thread pitch gauges at most real hardware stores.

 

[Brian1]

It uses 12mm x 1.75 metric bolt

The 12-point factory bolts are Ford P/N N800594-S100, should be a few bucks each

New shaft looks nice!

 

[D.R.Ball]

If they are 12 point use the same size 6 point as long as they are the same grade 8 etc.12 point verses 6 point will not matter for the bolt unless it's a clearance issue, just make sure the grip length, thread pitch and overall length are the same and use what you can find.

 

[Maniak]

I did. He looked. No dice. Maybe I'll look online tonight and try a different store.

If you can't find them and really want to stay stock, let me know.. I'm pretty sure I have a set (4) lying around here that you can have for the cost of shipping (IIRC, small flat rate box is $5.80).

~Mark

 

[2TimingTom]

The 12-point factory bolts are Ford P/N N800594-S100, should be a few bucks each

Thanks for the part number. $2.74 with tax. Worth it. Admission to the junkyard near me is $2. So I paid an extra $0.74 to sit in a chair while they got the screw instead of laying under a potentially unsteady truck.

Got it installed finally.

The driveshaft guy said to install the splines down. The reason is that the driveshaft presents a smaller cross section like this and gives a little more clearance to obstacles this way.

 

[D.R.Ball]

Good job, however much to about nothing, you could have used 6 point bolts and been done with it. There is no reason why you needed a 12 point bolt when 6 point of the same thread size and grip length would have done the same job, with out all the drama.

 

[2TimingTom]

Could have. But now if I ever need to go under there again, I take one tool with me instead of 2. And the generic bolt of equal strength would have saved me like $1. So instead of me digging through the fastener bins at Ace Hardware looking for a match, I rolled up with a P/N and he came back with the proper fastener. Plus Ace Hardware doesn't have a 2015 Mustang to sit in and check out and make vroom-vroom noises.

And why do you care so deeply about which fastener I used anyway? Talk about drama.

 

[malohnes]

Ditto on the nice shiny shaft comment!!


Can I ask what the shop charged you for it?

 

[2TimingTom]

Can I ask what the shop charged you for it?

I can take a look tonight. If I remember right, it wasn't too bad really.

 

[2TimingTom]

$235 out the door.

 

[malohnes]

Oh, thats a fair bit less that what I expected. Thanks

 

[malohnes]

Almost a year later...how's the shaft holding up?