Driveshaft bolt predicament

[ntsqd]

I'd say the bolts are subject to both tension and shear forces; when the driveline is working, there is a continuously-varying interaction occurring. What exactly do you mean by first tension and secondly shear? Do you mean primarily tension?

I doubt there would be any compression/tension forces in the bolt with the slip joint in the shaft. I would think the only normal stresses the bolts would see is would be from the tightening torque?

Essentially what Mace said. The bolts are not in shear normally. They are tension bolts and their job is to hold the flanges together tightly enough that the friction between the flanges transmits the torque. Their shear strength alone is not likely strong enough, but their fit to the holes needs to be good enough that their shear strength can supplement the friction if the friction isn't quite enough for what-ever reason. I keep coming back to the same example, but flywheel bolts work this way too. You don't just use any old bolt there, and you shouldn't use any old bolt here either. Grade 8 bolts border on being too brittle for either of these uses.

The bolts will be standard automotive grade. For SAE bolts, Grade 8 is what you want. For Metric, you want Grade 10.9. Grade 8.8 is often confused for automotive grade due to the similarity to the SAE grading scale but it should never be used to replace an automotive fastener. Most hardware stores will carry this grade of bolt, however the unusual size you are looking for is likely what makes it difficult to find them.

It is normal to have some play in the diameter between the bolt hole and the bolt so that it is easier to slide the bolt into place and the design tolerance of the bolt pattern is reasonable.

From the sounds of it, you are measuring 7/16" (.438") bolts that were probably used by the PO or a shop that did work on the driveline. These bolts are more readily available in automotive grade and are very close to your measured value of 11 mm (.433"). Even if you have a set of calipers that are accurate to the nearest thousandth, the threads on a used bolt could easily vary five thousandths from the nominal. If you can't fit the M12's then M10's were probably used originally. Toyota would not have used an M11 bolt on a vehicle. If more strength was required, they would have used a fine thread M10 or increased the hole size to M12.

If you want some light reading about bolts (and a number of other engineering topics for the Metric system) here is a link to the Metric Handbook in PDF.

If the 7/16" fit, go ahead and use the Grade 8 fasteners there. Just be sure you pick up the fine thread and not the coarse/standard thread as this makes a significant difference in strength. Also, be sure to use lock washers.

Most of this post is good info, but there is NO difference in strength between a coarse threaded bolt and a fine threaded bolt. There is a difference between the maximum install torques and the resulting bolt tension (& related clamp loading), but not in the ultimate strength of the bolt.

I have measured the holes in the t/C flanges in the process of having some custom flanges made that allow me to bolt Toyota flanges to a New Process t/c and those holes ranged from 11.25mm to 11.5mm. Very highly unlikely that they had 10mm bolts in them as the fit was too snug for there to have been 1.25-1.5mm worth of slop there. It is odd that they'd be 11m bolts, but no more odd than the M17 thread (tested to NOT be 11/16") used in one of the PS box ports.

 

[Cruiserdrew]

Would the 11mm drive shaft bolts from an 80 be any longer? 80s use the same diameter, but I'm not sure about length.

Regarding why a non-standard measurement of 11mm-here is my theory: Originally Toyota drive shaft bolts were 8mm. That was too small and too weak, and so they went to 10mm. That also had occasional failure problems, so they went to 11mm to avoid having to use different flange machining. That's a guess.

Anyway, a call to Cruiserdan would confirm what is in the pipeline from Toyota.

 

[disassociative]

Toyota used a 11mm bolt.

So they did! I was looking at the torque specifications for the rear propeller shaft in the FSM and mis-read the FT-LB spec as the N-m spec. It happens to be 65 which is the torque spec for the M10 Grade 10.9 bolt, my bad

The torque spec for the 7/16" Grade 8 bolt is 78 FT-LB, and the clamping force is higher than an M12 10.9, so if it fits, it is more than strong enough.

If you really want the M11, it is available for $1.31 according to toyotapartszone.com: link here

 

[laguna80]

I just used 10.9 metric M14 course thread hex bolts with lock washers on my fj60 rear driveshaft mating to the differential. Is this wrong then? Will they not hold up? Just replaced them because the previous owner had a mixture of bolts under there that kept coming loose.

 

[Mace]

M14, or 14mm head bolts?


They are not correct wither way. Will it ever make a difference? I can't tell you that. Can it make a difference? Yes it can..

 

[Randy88FJ62]

M14, or 14mm head bolts?


They are not correct wither way. Will it ever make a difference? I can't tell you that. Can it make a difference? Yes it can..

He must mean M11 with 14mm heads.

 

[laguna80]

He must mean M11 with 14mm heads.

I meant m14 with 17 mm heads. They fit but I can only tighten them down with the box end wrenches. Sockets won't fit.

 

[Mace]

I could not trouble you for a pic of this could I?

I cannot see how a 17mm head would fit on the standard LC DS yokes at all.

 

[ntsqd]

I can't see how a 14mm thread would fit in the same hole locations w/o breaking through the outside edge of the flange. It's gotta be really thin there!

 

[laguna80]

I could not trouble you for a pic of this could I?

I cannot see how a 17mm head would fit on the standard LC DS yokes at all.

Here's a pic I just took. I assumed I have standard yokes, but I don't know for sure. The truck was as stock as could be when I got it.

 

[Randy88FJ62]

Here's a pic I just took. I assumed I have standard yokes, but I don't know for sure. The truck was as stock as could be when I got it.

To the best of my knowledge M14 diameter bolts are not stock on our cruisers. I have no idea why someone would do that but if it works then it works...

 

[IH8Wood]

Take your POS CV driveshaft + stock driveshaft to shop and have them make you the right stuff. They can also lengthen the slip yokes cause you know you're gonna want that.

 

[astr]

There at least three standards for metric bolts. The most common ones are ISO/ANSI, JIS, and DIN. Toyota and most Asian car manufacturers use JIS whereas the one that you buy at the hardware store are usually DIN. That is why a M10 bolt on your truck will have a 14mm head whereas the same bolt from the hardware store will have a 17mm head. Here is a table: Metric Bolts - Head and Wrench Sizes

 

[cruisedeisel]

drill it, its fine. did mine 4 years ago. no problems so far. cheers