STICKY FSM (Factory Service Manual) Corrections

My approach to fuel capacity before a trail ride is just like it is before an airplane ride- Fill the blame thing up!!
 
Some FSMs list the torque for the Dana 30 and Dana 44 ring gear bolts (most are 3/8-24) as 100 ft/lbs. This is incorrect, any engineering textbook will tell you the correct torque for a grade 8 3/8-24 bolt is around 50 ft/lbs.

https://www.almabolt.com/pages/catalog/bolts/tighteningtorque.htm

this was brought up recently in another post about loose ring gear bolts IIRC.............. scares the crap out of me, the JK Dana 44 axles some of us are using have FSM ring gear torque values stated at 135 ft lbs.
the torque for a 1/2" gr8 bolt is like 80# and your between 9/16 and 5/8 to hit that 135# mark.
are they really stupid enough to keep making the same mistakes over and over in different FSM's? i even called RGA b4 i did this trying to confirm this info......all they said was their stuff could handle it, not whether it was right or wrong.
 
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this was brought up recently in another post about loose ring gear bolts IIRC.............. scares the crap out of me, the JK Dana 44 axles some of us are using have FSM ring gear torque values stated at 135 ft lbs.
the torque for a 1/2" gr8 bolt is like 80# and your between 9/16 and 5/8 to hit that 135# mark.

Are the ring gear bolts torque-to-yield?
 
Are the ring gear bolts torque-to-yield?

IDK honestly, when looked for this spec everything i found said 135#. so that's what i did, even had to make a gizmo to hold the locker so i could get that much force to the bolts.

what scares the crap out of me is i stumbled into another torque list months later that said 135Nm and i'm worried everything i found was bad info copied from 1 bad source to another.
TBH IDK if i ever looked at an official JK FSM, i googled it and read through several JK torque rate lists and they all said the same thing as far as i recall. i didn't feel right about it and made calls to try and figure it out but nobody gave me a straight answer.

either way it's done and i'll have to suffer the mistake if it is. the axle still needs some break in miles and an oil change so i'll definitely inspect them when i get back in there.

here is 1 of the lists i saved because it had multiple axle info on it (from crawlapedia).

gear spec.PNG
 
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05/06 wiring diagram manual has the #4 clutch bypass fuse as just shorting out the clutch switch. Its tied to the ecu somewhere. The 4wd light comes on, the idle rises a bit, and it eventually resets to not being bypassed anymore.
Cutting/shorting the clutch switch wires at the switch doesn't turn on the 4wd light, or raise the idle and is a permanent bypass.

There were other errors in the wiring section, but I dont remember them off the top of my head
 
are they really stupid enough to keep making the same mistakes over and over in different FSM's? i even called RGA b4 i did this trying to confirm this info......all they said was their stuff could handle it, not whether it was right or wrong.

I used to know someone who wrote automotive tech manuals for a living. She was neither an engineer nor much of a mechanic. They're like actors...they work from a script and as long as it's all spelled correctly, that's the end of their proof-reading skills.
 
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Compared to the 99 XJ FSM, the TJ FSM's are the gold standard. Trying to get Xj Buddy's OBDII reader to connect....there are so many tiny mistakes in the wiring diagrams, extra complicated because there was a diesel version that changes tons of stuff. In particular there are 2 grounds on the data link connector that go to G102, but the grounds diagram only has G102 listed on the diesel version. I may have to find the corresponding circuit on the 99 TJ and pray they ground the same way.

So yeah, let's remind ourselves how lucky we are to not be XJ owners.
 
I used to know someone who wrote automotive tech manuals for a living. She was neither an engineer nor much of a mechanic. They're like actors...they work from a script and as long as it's all spelled correctly, that's the end of their proof-reading skills.

Like some of the pictures, I gather!

Screen Shot 2023-01-05 at 10.33.45.png
 
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This is minor, but my 97 FSM doesn't list DGA as one of the transmission options. See second page of posts here.
 
Some FSMs list the torque for the Dana 30 and Dana 44 ring gear bolts (most are 3/8-24) as 100 ft/lbs. This is incorrect, any engineering textbook will tell you the correct torque for a grade 8 3/8-24 bolt is around 50 ft/lbs.

https://www.almabolt.com/pages/catalog/bolts/tighteningtorque.htm


this was brought up recently in another post about loose ring gear bolts IIRC.............. scares the crap out of me, the JK Dana 44 axles some of us are using have FSM ring gear torque values stated at 135 ft lbs.
the torque for a 1/2" gr8 bolt is like 80# and your between 9/16 and 5/8 to hit that 135# mark.
are they really stupid enough to keep making the same mistakes over and over in different FSM's? i even called RGA b4 i did this trying to confirm this info......all they said was their stuff could handle it, not whether it was right or wrong.

When I had issues with my ring gear bolts backing out, I did some research and this is what I came up with - at least regarding the Dana 44 in my TJR:

  • Ring Gear Bolt is PN 45784 and is 7/16-20
  • This spec for 45784 says it is Grade 8, but note in the picture there are 7 lines; Gr 8 has six
  • This spec for a kit of 45784 says it is Grade FW-9, which I can't find much online about but I was able to find one image showing a Grade 9 hex head with seven lines:
Screenshot 2023-02-15 133419.png



So I'm assuming the strength of the bolt is somewhere between Gr 8 and Gr 9, but I'll use Gr 8 specs for the next part to be conservative:
  • The recommended torque (clamp load) for a Grade 8 7/16-20 is about 80 ft-lbs dry and 60 ft-lbs lubricated
  • FSM says to install to 100 ft-lbs and makes no mention of Loctite
  • Proof load for 7/16-20, unlubricated, would be around 100 ft-lbs
My conclusion is the FSM intends for the ring gear bolts to be installed without loctite and torqued to proof load, which would explain why they make very clear to use new ring gear bolts (because the spec calls for the bolts to be torqued near the yield threshold) each time.
 
Hi @Chris,

Since this one has been sleepy for a bit, what about we make another one to collect PDFs of all bulletins?

My post here has a way to gain access to all bulletins with a short-term subscription. I downloaded a lot of them, maybe all of them, when I did a trial run.
 
Hi @Chris,

Since this one has been sleepy for a bit, what about we make another one to collect PDFs of all bulletins?

My post here has a way to gain access to all bulletins with a short-term subscription. I downloaded a lot of them, maybe all of them, when I did a trial run.

Are you suggesting we make that other thread a sticky or make a new thread altogether?
 
Are you suggesting we make that other thread a sticky or make a new thread altogether?

Oh I was thinking we just make a new thread all about bulletins, like this one about corrections.
 
Oh I was thinking we just make a new thread all about bulletins, like this one about corrections.

Since all these threads already exist the better idea might be to have a resource thread (or table of contents so to speak) with individual links to all the manual, service manual, bulletins, etc.
 
Since all these threads already exist the better idea might be to have a resource thread (or table of contents so to speak) with individual links to all the manual, service manual, bulletins, etc.

Sure, makes good sense. And yes, I see your point because that's roughly what I was starting in the thread I linked above.

We could add to that by making a thread or a post with all the bulletin PDFs, like we have for the FSMs.
 
Sure, makes good sense. And yes, I see your point because that's roughly what I was starting in the thread I linked above.

We could add to that by making a thread or a post with all the bulletin PDFs, like we have for the FSMs.

That would be a good idea, yes!
 
Do we consider the diff cover bolt torque spec of 30lb-ft (p3-144 and 3-152) to be an error? From what I can tell they are 5/16" bolts and my Fastenal chart doesn't show any 5/16" hex head of any grade or thread pitch rated for that, with ASTM A574 fine thread, socket head cap screws being the lone exception.

If I'm wrong about this please let me know, and why.
 
Do we consider the diff cover bolt torque spec of 30lb-ft (p3-144 and 3-152) to be an error? From what I can tell they are 5/16" bolts and my Fastenal chart doesn't show any 5/16" hex head of any grade or thread pitch rated for that, with ASTM A574 fine thread, socket head cap screws being the lone exception.

If I'm wrong about this please let me know, and why.

I would have sworn they were 7/16 but I’m wrong all the time. If we can prove that the spec is wrong, then I’d love to call it out.

But I’d also love for us to get these corrections actually into the relevant sections of the doc. The incorrect valve body thing that spawned this whole discussion bit somebody a few weeks ago, and I was troubleshooting with him and I didn’t even remember that this issue was documented AND that this thread existed. 🤦‍♂️
 
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