67 Transmission Rear Mount Bolt Questions
The 67 AIM in UPC 6 indicates bolt part number 9419073 for the bracket to the rubber mount and bolt part number 454933 for the rubber mount to the tail housing. What is the difference between these two bolts (i.e. length, head, etc)? I have a factory side exhaust car without the U-shaped exhaust pipe hanger clamp. Is it correct to assume that for the side exhaust installation without the clamp bracket (UPC 8) that the transmission is slightly lower in the rear? The clamp is sandwiched between the mount and tail housing and is not present for the side exhaust car. Attached are two pics of my bolts prior to disassembly. Note the headmarks.
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Re: 67 Transmission Rear Mount Bolt Questions
Your assumption is correct. I believe the '69 N14 cars used a spacer, though. Also see that Long Island offers a spacer for C2 side exhaust cars (Section 33, #42) to re-align the transmission to where it would have been with under-car exhaust, even though this is not factory. Been thinking of getting one of these myself
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Re: 67 Transmission Rear Mount Bolt Questions
Recently I ordered a mount from LIcorvette and when I installed it it was the thickness of the bracket to high causing the pipes to hit the top of the tunnel. Maybe that is the mount that is used on the side exhaust cars. I then bought one from NAPA that was the right hight. When I called LIC they jumped my a&& and I couldn't get a word in edgewise. I only wanted to head off future problems but they wouldn't let me talk.
DOMComment
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Re: 67 Transmission Rear Mount Bolt Questions
Thanks for the feedback guys regarding the effect on alignment without the hanger clamp. I'll keep it stock i.e. without a spacer. You wouldn't happen to have any information regarding the mount bolts? I plan on re-installing my transmission over the holiday and want to use the correct bolts (including headmark) and washers.Comment
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Re: 67 Transmission Rear Mount Bolt Questions
Dereck,
All four of my 1967 transmission mount (GM 3792133) bolts appear to be identical, matching your Grade 5 bolts with the "M" headmark. All four are 7/16-14 x 1". Since the inner and outer transmission mount bolts have different part numbers (UPC 6-B6, Items 5 and 9), I suspect two of mine are incorrect, unless it was an assembly-line substitution situation.
In the first picture, it looks like the outer transmission mount bolts (6-B6, Item 9, GM 454933) have the "RBW" headmark with no grade lines (Grade 2), is that correct?
Your inner (or center) transmission mount bolts (6-B6, Item 5, GM 9419073) look identical to mine. The lock washers (Item 6, 103328) are probably the same or similar, but unless I am mistaken, the flat washers should be much larger than the ones in your picture.
The flat washer is GM 3700338 (6-B6, Item 7), and can be found in 1964 and earlier parts books (and possibly the 1965 book). The GM dimensions for this flat washer are: 15/32" ID x 1-3/8" OD x 3/16" thick. Using a tape measure, mine are 15/32" ID x 1-11/32" OD x 5/32" thick.
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Re: 67 Transmission Rear Mount Bolt Questions
Trans mount bracket to trans mount bolts are 7/16-14 x 1". Trans mount to trans bolts are 7/16-14 x 1-1/8". Grade 5 black phosphate. Special thick/wide washers are natural. Check the AIM it calls out different #'s for this application.
RichComment
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Re: 67 Transmission Rear Mount Bolt Questions
Rich, do you know when the trans mount to trans bolts became 1-1/8" long? This is what's throwing me off:
1963 used the same bolt for both positions (6-C4, GM 179858). I can find no data for this bolt.
In 1964, GM 454933 Bolt was added (6-B6, Revision Record, 10-10-63), taking the place of the GM 179858 Bolt that was used for the inner trans. mount bolt location in 1963. The outer trans. mount bolt in 1964 is listed as GM 9419073. No mention in the Revision record for this change, it may have occurred after end of 1963 production but before 1964 production began. These two bolts (454933, 9419073) remain in use through 1967, although they swap positions (inner for outer and vice-versa) for 1965-67.
The 1965-1967 AIMs (UPC 6-B6) show:
A) GM 9419073 (Item 5) for the INNER trans. mount bolts (was outer in 1964)
B) GM 454933 (Item 9) for the OUTER trans. mount bolts (was inner in 1964).
I have not found part listings for ANY of these three bolts. The closest I have found are the Illustrations for "1963-1967 Corvette Engine Mountings (Typical)". The illustration does not call out the part number, but shows the same picture as the AIM (6-B6) minus the shifter bracket (added for 1966, GM 3888263, Item 11, shown in 1966-67 AIMs). The Illustration shows the same Bolt being used for BOTH the Inner and Outer trans. mount bolts. It is labeled Group 8.900 and the dimensions for this bolt are given (7/16-14 x 1”).
I suspect the illustration has not been updated since the 1963 configuration. I realize we're only talking about 1" vs. 1-1/8" difference, I would just like to understand why the changes were made, because they experimented with the bolts and locations as if they were trying to solve a problem. It is also curious that none of these bolts show up in the parts books.Comment
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Re: 67 Transmission Rear Mount Bolt Questions
Scott,
Just a guess is in 63 when they switched to Muncies?? Only a guess. My understanding is the extra 1/8" was because this bolt went into the aluminum trans. The 1" bolt went into the steel insert in the trans mount. This 1" and 1-1/8" scenario applies to other GM Olds and Pontiacs from what I remember.
I have seen many diviations from the AIM and illustrated parts catalougs. I take my info from real world applications as well as written sources. I know real world applications can also be incorrect but in this case I overwhelming see the 2 different bolts in c-2's and c-3's.
RichComment
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Re: 67 Transmission Rear Mount Bolt Questions
Scott,
To add to the post remember that 63's did not use a steel mounted exhaust hanger between the mount. The 63 hanger is unique to only 63 and mounts to two tabs welded to the frame so maybe the longer bolts are not required.
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Re: 67 Transmission Rear Mount Bolt Questions
Thanks Rich. I forgot about the change from Borg-Warner to Muncie. If I understand correctly, the base 3-spd transmission was a Saginaw, and the 4-spd was Borg-Warner up to approximately VIN 15,000 (around May 10th) in 1963. From there on, it was a Muncie, when equipped with 4-speed.Comment
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Re: 67 Transmission Rear Mount Bolt Questions
Tim, thank you for the post. I have read here on the TDB regularly about the differences between 1963 and 1964-67, but having a 1963 assembly manual for comparison now is definitely helping me to get a better understanding. There have been many instances where having the AIMs and JGs from other model years has been very helpful in figuring things out for the '67 that I'm working on.
Trying to learn... slowly but surely... slowly, mostly
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