Rockn-Roll

I picked up a used carrier, clutch packs, clutch plates, and a clutch spring; plus, new bearings from Pacific Corvette in Puyallup, WA for a grand total of $235 including tax...not a bad deal compared to some of the used pieces forum members offered. Thanks for all the offers, but I need to get the car back on the road by Friday so I can drive it to Nintendo for the game testing project I scored. :) This is just a temporary fix anyway until I get around to installing a more durable differential. Does anybody know if a C4 or C5 differential can be bubba'd to fit under our stock suspension?

I need to know what the torque spec ranges are for the ring gear to carrier bolts, and the bearing cap bolts. The counter person at Pacific Corvette said 50ftlbs for both, but the ring gear to carrier bolts are 3/8" while the bearing cap bolts are 7/16", plus when I pulled the thing apart the ring gear to carrier bolts felt more like 35 to 45 similar to clutch plate bolts, or intake manifold bolts, and the bearing cap bolts felt more like 45 to 65 like rod cap bolts. I apparently need to get a service manual which covers the differential...anybody have a reliable documented source for the torque range, or a book that covers them? I think 50 is too much for the ring gear to carrier bolts, and too small for the bearing cap bolts.

Tom454

1970 Chassis Service manual says 50 for the Ring Gear bolts, and 55 for the bearing caps in the Specifications Section, Section 4, page 4

Rockn-Roll

Thanks! :cheers: You are the man Tom! Looks like I need to scare up a chassis service manual for my 75. I was sure the bearing caps got some extra torque. Though, I do find it odd that it's a specific torque, and not a range...new bolts normally work well with the lower torque, while old bolts sometimes require additional torque to hold as well as a new bolt...it has to do with plastic deformation of the threads, elastic deformation would not hold the bolt as well.

DeenHylton

The Richmond Gear instruction sheet also says to locktight the threads on the ring gear bolts...Deen

GTR1999

R&R,
I just rebuilt my 69's differential. THe ring gear bolts should be changed if you removing them,either way you should use red loctite on them and torque to 50 ft/lbs. The bearing bolts can and should be changed to socket head cap screws and torqued to 55-60 ft/lbs. I have some pictures if you want to see what I did.
Gary

Rockn-Roll

Thanks for the heads up Deen & Gary. I think I'll start with 35ftlbs on the ring gear bolts, and get a "feel" for how they settle in before torquing the extra 15ftlbs. Also, I think the bearing caps I'll bring to 40ftlbs, but will be taking them to 60ftlbs no matter what I think they feel like. But, I never use Locktite on my threads, and rarely use new bolts when the old ones are still in great shape. I've never had any bolts fall off even during my three year duty as fleet mechanic for a dozen vehicles, and I've swore enough for the bolts that I encounter which obviously had locktite cause the torque required to remove the bolts are almost twice that of what was certainly used to put them on...snapped several bolts in the process. But, hey...now I'm an expert at center drilling and tapping new holes within 1/32" of the original with a hand drill at that! One of these days I need to get a drill press.

Tom454

It all ties back to that deformation, or elongation, or ..... bation.... that you mentioned.

Bolts are torqued to a "number" only as an approximation of the intended end result.... bolt stretch. Technically, critical bolts need to be stretched a given amount in thousandths of an inch in order to produce the correct clamping and retention friction. Torqueing is merely an approximation, as measuring stretch is not viable in many situations (for example, head bolts). Since all fasteners are produced to have qualities that fall within a range, (statistical sampling is used in the production process) torque specs are also occasionally given in a range... all bolts will not require the exact same torque to arrive at the same stretch spec.
After bolts are stretched per spec, they sometimes lose their ability to be accurately stretched a second time... they become "plastic", or no longer useable for the intended application. This is why GM (and others) recommend not to re-use certain fasteners... specifically the ring gear bolts.
I have had bolts lose their ability to be stretched (torqued)... the torque figure is reached, and the bolt can be felt twisting when the threads are not turning. It's that "feeling" you experience with a bolt just before it snaps off. The metal is fatigued and the bolt is useless.

Sometimes you can get away without following the rules, sometimes you can't.