1936 Buick Special Ring gear Rivets broke - HELP!

[Buick36-49]

Hello All,

Recently while coming back from a car show (60 miles round trip) in my 1936 Buick Special, at the bottom of my driveway the ring gear rivets went in the differential leaving me stuck.

Has anyone tired to put the ring gear back on with harden cap screws or bolts? If so, what is the correct length, width and toque specs?

I want to avoid having rivets put back in. The ring and pinion gears are not chipped, or broken. I also had the correct level of gear oil as well. What could possibly cause this? Everything is stock. Car has about 92k on the odom.

Any advice or suggestion would be appreciated.

Thanks

Robert

[Mark Shaw]

I expect the gear lube may have become corrosive at some point in the life of the car... This could be from water in the oil or just old lube that can become acidic over time by absorbing moisture from the air during heat and cold cycles.

Most people do not consider that fasteners corrode from all sides. This doubles the failure rate for round stock compared to flat stock.

High stress fasteners are also subject to accellerated corrosion at stress points due to heat and flexure.

[50jetback]

The rivets that fix the ring gear to the case are listed as Rivet, special pan head in the parts book.

I believe the size is 5/16" X 1 1/4" ( well 1934 Series 40 and I don't think they would have changed by 1936 )

When I replaced the pinion and ring gear on my 1934 I tried to source bolt/nuts to replace the rivets but couldn't come up with any which had a thin enough head to give clearance between the case and third member housing - which is why they call the rivets " special pan head " I guess.

Bolt, locking nuts and lock-tite would work as long as you can find bolts with a very thin head.

At the end of the day I souced some mild steel rivets and went through the re-rivetting process ( you need a mate to help with this - extra hands to hold gas torch etc ). Check ebay for rivets - blacksmith suppliers and the like still stock them.<!-- google_ad_section_end -->

[Buick36-49]

Thanks for replying both Mark Shaw and 50jetback. Also, thanks for giving me the dimensions of the bolts. This will be tricky. I have a 1949 Buick Super Series 50 along with the shop manual that explains that you must re-rivet the ring gear back on. But for the ’49 there does not seem to be much tolerance for the heads or nuts if you wanted to switch from rivets to bolts. However, while playing around last night with ’36 I’ve stuck in some cheap regular bolts with large heads about the size of the rivet heads on both sides of the case and ring gear. I guess my concern would be if the nuts would hit the pinion gear, but they did not. So, that what I am going to try finding is some grade 8 bolts and nuts.

Robert

[Mark Simmons]

Robert, Stuart and Mark's advice is very good as always! When you were playing around with the nuts and bolts on the ring gear was the entire assembly in the housing ? If not try it with the entire R&P in the housing. If the #8 nuts and bolts work great, but remember if you grind the heads of the bolts you are losing strength. I suspect that you'll find as did Stuart that rivets are the way to go. Just my 2 cents from experiences. Mark

[Buick36-49]

Hello All,

Thanks for helping me along with the project! I have a most no time work on this between working to jobs. BUT, I did find time to get the parts I needed with the help of you guys guiding me.

I did manage to find some 5/16 grade 8 bolts from a small hard ware store. I am not thrilled that the bolts don’t have spacers and are threaded all the way to the head, but I think if I torque them down tight enough (start at around 35lbs cross tighten, then final tighten at 50 – 60 lbs) that should not move or get loose, I am also buying some lock nuts as well. These old ring gears have a 12 rivet pattern, that I am substituting bolts for. I also, put some bolts on last night and then spun the rear, nothing seems to bump or hit the case or the pinion gear!! So my fingers are crossed that this will work.

I’ll keep you all posted

Robert

[Barney Eaton]

According to the Machinery Handbook, a 5/16 (button head)socket cap screw has a head no more than .176 high, the diameter of the head is .688 minimum, giving you good support. These I believe equal to a grade 8 bolt and should be available at most places that sell screws.

[Buick36-49]

Hell All,

1936 Buick Ring gear fixed!! This project was not too bad. The hardest part is to remove the old rivets that got sheared off in the first place.

1. We had to make a punch that could fit in holes in the carriage and then penetrate to the ring gear.

2. Next is to drill out the rivets about 1/4(suggested from my 1949 Buick shop manuel). This was hard because I kept breaking drill bits.

3. Once the rivets were weakened, you can just pound them out with a sledge hammer and a punch.

4. Next, would be to insert the Grade 8 5/16 bolts that are about 1.25 inches long. I was lucky enough to find bolts that did not have big heads or nuts.

5. Install them with lock washers and torque them down to about 40-50lbs.

I will be uploading a video sometime on youtube of the ring gear in action with the bolts.

Thanks for all your help.

Robert

[Buick36-49]

1936 Buick Special ring gear fixed using grade 8 5/16 1.25in bolts.