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My experience with the snubbers is that on leaf spring cars there is significant snubber movement, and if it changes the driveshaft u-joint angle enough, the angle change becomes a problem. U-joints are most efficient at 90 degrees, and are weaker at other angles, leading to easier breakage. (aka Dodge pinion snubbers) But this has almost no impact on a C3.
But the other thing that rubber bushings do is they let the diff rotate, and rebound, with power or traction pulsing on/off. With any inconsistency in tire traction, as in slippage, gripping, hooking-up, pothole, etc. etc. you can get into wheel hop. C3s can get into serious wheel hop with rubber bushings, and there is no shock absorber in this direction that dampens this oscillation (as Mustang quad-shocks do), so once it begins, it can get quite severe. And this hammering will break already marginal IRS parts. Spinning the tires is not the problem, it is when they are beginning to hook up.
The 70s Baldwin Motion C3 solution was a diff mounted C3 traction bar.
I'm going delrin diff mounts for this one reason, to prevent wheel hop, and protect my IRS parts.
Thanks. I was hoping somebody with a position on this would weigh in. The most severe duty I've put my car in has been autocrossing and I've never experienced any of the maladies you've mentioned. I did have to adjust my driveshaft angle and remember cutting down the front snubber some, which means less total flex. On the crossmember I've replaced the attachments there with something that has a big aluminum circular plate but I've forgotten all what that is except to reduce movement.
As to the differential mounting, if you want to go completely hard core, here's what's in the Chevy Power guide. A bit too harsh for me. As to why, I suppose this eliminates any compliance change with the chassis that affects wheel alignment. That's about all I can come up with.
On the Van Steel Delrin bushing kit it replaces the rubber crossmember bushings for Delrin bushings, then an aluminum plate is installed once the crossmember is installed.
That bushing also helps with driveline alignment. I think I recall you are swapping in a 5 speed. When you drop the new powertrain in the chassis, be sure to make sure your driveline angles are aligned. Cutting that puck down is one way of changing the diff angle to get it right. I know after I hard mounted my rear crossmember and swapped in the TKO I had to adjust the thickness to get the alignment correct. You may or may not need to do this. Usually just depends on how many changes you make, each change takes something a little further from design time...
I ran a Poly bushing on the pinion for a good while. It ended up cutting a perfect hole through the frame mount....looked like a hole punch had done it!
I fabbed a new frame mount out of 5/16' steel and installed a stock bushing. I also have stock bushings on the sombrero mount with a set of the aluminum plates. For extra insurance I did fab a little wing that extends out underneath the welded in crossmember behind the diff and dropped 4 bolts down through it. It helps take a load off that front mount.
Now I DO tend to abuse things a little more than most...but it's been doing this for the last 27 years.
you are over torquing it if you are stripping a grade 8 bolt and grade 8 nut at 70 ftlbs
My torque wrench was set at 55 ft lbs when I felt the threads start to go.
I double checked to make sure my torque wrench was working properly by using my second torque wrench with the same feel and result.
I torqued stuff today without any issues.
On the Van Steel Delrin bushing kit it replaces the rubber crossmember bushings for Delrin bushings, then an aluminum plate is installed once the crossmember is installed.
Just a note: When you go to the aluminum disk ends depending on which kit the gain is also raising the differential mounting point by up to 1/2 inch. I posted pictures years ago about modding the rear snubber bracket mounting bolt hole. Mine is higher to allow the front snubber mounting to go up. I use an aluminum shim disk that I made to make the differential as ridged as possible. A CF member by the name of 66impala or something like that from Placer Ville lake California actually did cutting and channeling the rear differential cross member mounting point even higher.
Just a note: When you go to the aluminum disk ends depending on which kit the gain is also raising the differential mounting point by up to 1/2 inch. I posted pictures years ago about modding the rear snubber bracket mounting bolt hole. Mine is higher to allow the front snubber mounting to go up. I use an aluminum shim disk that I made to make the differential as ridged as possible. A CF member by the name of 66impala or something like that from Placer Ville lake California actually did cutting and channeling the rear differential cross member mounting point even higher.
Correct, the kit does raise the crossmember up into the frame.
The shorter Delrin cushion allows the snubber bracket to be mounted up and closer to the frame mounting point.
My kit did not include the delron ring. I have metal differential cross member to metal frame rail contact.
The other day we were out testing my friends road racing GT40 347 ci Ford 528 hp and I said now let's hop into my vette and show you how it's really done. I have about 90 more ci and a higher hp per pound.
I will be interested to hear or even see how well your 496 ci does fast launches 😁
My kit did not include the delron ring. I have metal differential cross member to metal frame rail contact.
The other day we were out testing my friends road racing GT40 347 ci Ford 528 hp and I said now let's hop into my vette and show you how it's really done. I have about 90 more ci and a higher hp per pound.
I will be interested to hear or even see how well your 496 ci does fast launches 😁
That sounds like a fun ride.
I haven’t driven anything with four wheels and a stick shift in 30 years and that was a 93 Jeep with a 4 cylinder.
It may be a while until I do any hard launches.
One thing that might help is to loosen the nuts on the sombrero mount/aluminum discs to let it move a little while tightening the pinion mount. Then tighten the sombrero mounts bolts afterwards.
One thing that might help is to loosen the nuts on the sombrero mount/aluminum discs to let it move a little while tightening the pinion mount. Then tighten the sombrero mounts bolts afterwards.
JIM
Thanks Jim,
I have considered that as well and will probably loosen the sombrero mount bolts then tighten all three points at the same time to their full torque.
Santa is bringing me a new torque wrench for Christmas.
I’ll use it to check my two older ones to verify the are right on.
They feel like they are within calibration but they are over 20 years old, so we’ll see.
I got one of those digital add on deals to allow you to use a regular ratchet as a TQ wrench from Harbor Freight. I had seen some accuracy testing that showed it as pretty good. I tested it against a recently calibrated Snap On TQ wrench as well as several others I have and the darn thing was dead on the money. I use it to test the calibration from time to time.
Truthfully a HF TQ wrench tested dead on also against the Snap On I've had since 1979 (which I have calibrated from time to time).
I started testing them as it seemed like when I started using a "stretch gauge" to measure rod bolts...I was finding every single one of the ARP's took a LOT more TQ to achieve the proper stretch than the ARP provided TQ specs provided (using their lube and burnishing etc). Turns out there must be a LOT of engines running around with bolts not torqued to the amount needed to get the proper stretch. It was eye opening!
And this was on ARP 8740's, 2000's and 625's.....all took a LOT.
YES! When I solid mounted my crossmember I had to modify the front mount like in this thread as well. For me it was one of those, "Huh, look at that, guess that needs to be modifed too" moments. Don't remember searching. I guess I feel better now knowing it's not just a result of some dumba$$ move on my part .
+2 on measuring rod bolts with a stretch gauge.
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