torque spec
I am installing the rear differential on my 66. Is there a torque spec. for the bolts for the rear frame differential crossmember?
Thanks
Mel
Thanks
Mel
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Re: torque spec
Have you looked in the '66 AIM?
Duke -
Re: torque spec
Wow Duke you're up early! I have my AIM handy so I'll jump in.....
Mel, the 4 bolts holding the top of the Differential to the Crossmember ?
or
the 2 bolts holding the Crossmember to the frame at the sombreros ?
See AIM UPC 4 Sheet B3, Item 2 BOLT for either application.
Next to Item 2 part#, ref the #2 inside the triangle, which is the torque spec, lower left on page, 55-65lbs/ft.
But note the different part# lock washers at each location. Why different for the same size bolt? I have no idea.
RichComment
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Re: torque spec
Correct torque for the two bolts that attach the axle cross member to the frame has always been somewhat of a mystery to me. From memory the '63 AIM says 35 lb-ft, but later AIMs (I dont' recall the years) specify 60-65 lb-ft.
Since the weld nuts are usually not heat treated (because the weld temperature anneals them if they are hardened), I wonder it they will take that much torque without possible stripping.
DukeComment
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Re: torque spec
Hmm, now that you mention, I always cringed when tightening those 2 sombrero area bolts on all my chassis restorations. I think I've just used the "feel-good-and-tight" method for fear of stripping them.
Thanks Gary, I knew there was some discussion at some time but forgot. Odd that the AIM still described the #446212 as a "L" washer. Likely a simple typo.
RichComment
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Re: torque spec
I just installed the differential in my '65 last Sunday. The two differential crossmember bolts that bolt it to the frame had lock washers on them when I removed them, and the differential had never been out of the car. I believe I went with the AIM torque spec of 35 pounds. I'll have to verify that when I get home today.
JamesComment
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Re: torque spec
Interesting,
I just looked in the '65 AIM and those(4) bolts holding the Diff to the crossmember were Item 3, part# 454932(7/16x14, 1 1/8" long).
Torque spec 45-55 lbs/ft.
Item 2 sombrero bolts, part# 454933 (7/16x14, 1" long)
Torque spec 55-65 lbs/ft.(WRONG! AIM shows 20-30 lbs/ft My typo)
In 1966, Item 3(454932) was deleted, and then Diff to the crossmember used the same as the Item 2 sombrero bolts, part# 454933 (7/16x14, 1" long)
Torque spec 55-65 lbs/ft.
I think they forgot to change the torque spec on these 4 locations, and just used the same reference as the other 2 sombrero locations. Those 2 go into steel weld nuts, the 4 for the Diff go into cast iron.
Edit... The following statement may be wrong. See Post #15.
Now I'm thinking the 1966 AIM torque spec is wrong(55-65 lbs/ft) for the 4 Diff to the crossmember bolts, part# 454933 (7/16x14, 1" long). I'm thinking it should be 45-55 lbs/ft. I think they missed the torque spec difference in the '65 AIM and assumed to use the same sombrero bolt highrer torque spec for the 4 Diff bolts.
BTW, the 1967 AIM shows same info as 1966.
RichComment
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Re: torque spec
Thanks to all. Also some very interesting information!
MelComment
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Re: torque spec
The two bolts that bolt the crossmember to the frame at the sombreros.
Thanks
MelComment
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Re: torque spec
Mel, Deep in my earlier post I said.... Torque spec 55-65 lbs/ft
But as mentioned, you want to make sure you don't strip the embedded weld nut threads, so you may want to go on the relaxed side of the spec, or less. Best to clean the threads of the weld nut with a thread restorer(not a Tap), and if you apply any Anti-Seize on the bolts, go even less on the torque.
RichComment
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Re: torque spec
Gravity pretty much holds the axle cross member to the frame, so I don't think those bolts need much torque, but like the main battery turrets on the battleships Bismark and Yamato, it might fall out if the car capsizes.
DukeComment
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Re: torque spec
I took a picture of the applicable page in my 1965 AIM that covers the differential crossmember installation. As you can see, the torque specification for the two bolts is 20 to 30 lbs./ft. I usually shoot for the mid range of the torque specification so I torqued them to 25 lbs./ft.
JamesComment
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Re: torque spec
James, I'm glad you checked that. I misread my 1965 AIM page. I corrected my earlier post re 1965.
However..... The 1966 AIM states 55-65 lbs/ft for that same crossmember to frame bolt location. Something is in error. But 25 lbs/ft seems a bit shy for a 7/16-14 bolt to me.
At this point I don't know what's right and what's wrong.
1966 AIM
1966_UPC4_SheetB3.jpgComment
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Re: torque spec
The plot thickens.
Crossmember to frame sombrero bolts #454933.... This was a Grade 8 bolt.
1963 Torque spec was "initially" stated as 20-30 lbs/ft, then it changed to 55-75 lbs/ft on 4/23/63
1964 Torque spec 20-30 lbs/ft
They realized the error in March of 1963, but it never got translated to the 1964 OR 1965 AIM. Then it got noticed.
I believe the 1964 AIM is wrong, as well as the 1965 AIM is wrong, and it got corrected in 1966/67 to 55-65 lbs/ft)
They got this confused for years. Summary: I believe the correct torque spec is....... 55-65 lbs/ft. No way would I trust 20-30 lbs/ft.
Rich
Ref AIM pages
1963_Sec4_Sheet5_RearSusp_to_Frame.jpg
1964_Sec4_SheetB3_RearSusp_to_Frame.jpgComment
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