I always like to add, whether solicited or not, that this little guy fits in that space and zips those 12-pt bolts out no problem.
CV joint ripped boot
- Thread starter boybach
- Start date
Interesting.
I just pulled the axles from my parts coach using a 3/8 box end Barcalo wrench with a larger wrench on the open end for leverage. By the time I finished, the little wrench had an obvious bend LOL
It becomes a tedious task trying to use ratchets or wrenches in that space for sure! I was quite pleased, when working on my second coach, to discover that little impact actually fit where I needed it to, and had plenty of oomph. Particularly since I like to Loctite the snot out of those things since I reuse the originals.
Need to get me one of these. I used a socket wrench and crowbar to keep the axle from moving. Lots of back and forth adjustments…
Planning on doing the boot replacement on Monday. Picked up the boot and bands from Napa. The band tensioner arrives tomorrow, so all ready to go ...however, if it turns out to be a problem to separate the CV from the axle on the coach, I thought I'd have a backup plan ready to remove the axle and do the job on the bench.
If I DO have remove it completely and the axle bolts can't be reused, I'd like to buy some new ones today just in case I need them.
I saw on the link page they are grade 8 but didn't find the info on the size or torque - anyone know the specs and how many I need for these bolts at the final drive? (coach out at storage area at the moment)
Thanks
Larry
If I DO have remove it completely and the axle bolts can't be reused, I'd like to buy some new ones today just in case I need them.
I saw on the link page they are grade 8 but didn't find the info on the size or torque - anyone know the specs and how many I need for these bolts at the final drive? (coach out at storage area at the moment)
Thanks
Larry
Last edited:
This is what I, and many in the community, use -
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
You really, really don’t want these loosening up, so be sure to use washers. I also added a dab of Loktite blue to each.
Thanks! how many do I need and do you know the torque setting for these bolts?This is what I, and many in the community, use -
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.www.mcmaster.com
You really, really don’t want these loosening up, so be sure to use washers. I also added a dab of Loktite blue to each.
Last edited:
The manual says 75 ft-lbs for the bolts to the output shafts. That's a torque to yield number meaning that the bolt stretches and doesn't go back to its original length when it's unbolted. It's a permanent deformation. If the bolts are reused and torqued to the same value they'll deform more, it's cumulative. That's why the manual says to not reuse the bolts.
You would be wise to read the following thread:
There's a lot of information and a good discussion among some super smart people with real world experience. An example:
"My experience base as a fastener engineer for two different companies says that reusing these guys once would probably be just fine, the second time would be a little less fine (this would be the third stretch) and the third time would be real scary. Now, how do you count that??
I think I am going to stock two complete sets and carry one in the coach in the case something happens on the road.
Matt"
I use these high strength plated bolts, the socket heads are far superior:
Zinc-Plated Alloy Steel Socket Head Screw 3/8"-24 Thread Size, 1-1/4" Long
https://www.mcmaster.com/product/90128A367
One side requires 1" bolts IIRC, so verify before ordering.
I've done it. More importantly Bob Drewes posted it and he was one of the uber gurus.
When I first got into the GMC community I had some questions and contacted a number of the gurus, some still with us - Ken Henderson, Dave Lenzi, etc. They all said the same thing - call Bob Drewes.
Bob would work his way through some improvement on a John Deere over the winter, winter downtime for a farmer, and John Deere would send their engineers to his shop to take notes in the Spring. They would've hired him as a consultant but he didn't need the money!
This raises some questions for me, Todd. A dry 3/8-24 Grade 8 bolt is torqued to ~45 ft-lbs ('standard' torque charts vary quite a bit), which is ~85% of its proof load and provides a clamping load of 7875 pounds. Proof load is a working‑strength limit - the highest load that can be applied repeatedly without causing permanent deformation.
The same bolt lubricated (Loctite is a thread lubricant while the bolt is being installed) standard torque spec is ~35 ft-lbs or less. So if Loctite is used that ~45 ft-lbs is going to generate a lot more clamping force.
The McMaster bolts in the links above have a tensile strength of 170,000 psi (which is curious as Grade 9 is 180,000 psi). Assuming the OEM bolts are similar at ~170,000 psi, and they're torqued to yield at 75 ft-lbs, that's a lot more clamping force than the Grade 8s.
More from Matt Colie:
GMCforum: GMCnet » So about that LH drive shaft..
So about that LH drive shaft..
gmc.mybirdfeeder.net
Like I wrote at the beginning, I have questions. I haven't calculated clamping loads for the assembly, different fasteners, etc, and I know that Manny torqued the high tensile bolts to 65 ft-lbs with blue Loctite and called it good. And from other posts the reports are the bolts fall out, they don't break - unless you're removing them! So just keep an eye on them and safe travels.
I hear this repeated a lot, going many years back, and it is generally accepted as common knowledge.
Personally, I would challenge it, and I've yet to see a legitimate source for this. TTY bolts have a necked down region, and the steps from the neck to the full shank are gently tapered so as to avoid stress concentrations. That is not how these bolts are designed. Threads are never an appropriate yield zone--it's a minefield of stress risers. TTY bolt torque specs are more than a value too--it's a value plus some angular displacement (i.e. 50 ft-lbs plus 90 degrees). That angular displacement is where the deformation occurs. They approach yield level with the initial torque value, then execute the yielding process with a known, physical amount of stretch that can be calculated from the thread pitch and the angular displacement. That is the process that shouldn't be repeated. Torquing a bolt to specified value below it's yield threshold can be done repeatedly.
These are what Applied GMC sells:
Here's a conventional TTY bolt design we're all used to seeing on modern cylinder head bolts:
Flywheel/flexplate bolts are some of the shortest TTY bolts in the industry, but they still have a visible yield zone on them. Here are some Nissan flexplate bolts:
Where? I could be missing it somewhere (it is a length volume), or maybe I'm looking at a different version. I'm not seeing it in the X7525 manual. They do have this blurb that says, if it needs replacement the replacement should be equivalent:
Last edited:
That does raise a good question. What is the lubricity of Loctite and how much are we inadvertantly raising the clamping force by using it?
Thanks, I'd missed that bit.
I'd be willing to bet that was a conservative choice on GM's end, since they knew they were pushing the limits of proof load of the bolts. And if old ones were greasy/oily, you're not getting the dry-torque tensile load that the original assembly gets--you're getting a higher load as Richard points out. So while it's not a conventional TTY situation, replacing them is prudent for consistency sake.
Otherwise, a person has to:
- Ensure they're carefully clean and dried
- Check them for past yielding like Matt Colie described in the other thread
- Potentially adjust torque values for wet-application with a locking compound if desired
Unfortunately the uj3415 arrived and is only long enough for a single wrap
