gkull

IGNATZ, I would say that you have way too much free time on your hands!

gkull

I made my own and bigger before I saw them online. keeps the differential from ripping the bolts out of the cross member when you solid mount the ends

https://www.racevette.com/store/p9/C...s_1963-79.html

Richard454

That is Mark's build- not "stock" either but a 76 with a Gen VII Big Block- a lot of work done on it.

The build- https://www.digitalcorvettes.com/for...d.php?t=148376
And the post on the diff /driveline work- https://www.digitalcorvettes.com/forums/showpost.php?p=2232426&postcount=280

corvettedave383

Had another go at this stuff today, i tryed bolting the diff tail to chassis, metal to metal no bush, ends up at about just above zero degrees, so to get it up at 2 degrees up would mean having to re fab the diff tail bracket and then to go up that much, you would be so close to hitting propshaft of the trans tunnel near diff with prop

so with the poly bush in and bolted up tight, squeezing a little, i end up with a 2 degrees downward angle on diff and trans/engine is going down 2 degrees, so i end up with the perfect W configuration

Iam thinking the ploy bush will reduce movement alot compared to rubber bush, therefore less chance of stuff breaking hopefully

so just going to try this and see how it goes

ignatz

Same amount of static torque regardless of which bushing you pick, but have a look here.

https://www.corvetteforum.com/forums...e-bracket.html

Also note Willcox's comment. Best to do your own research, but this I remembered.

corvettedave383

ok very interesting, got rubber version ordered up, so easy enough to swap over

Metalhead140

Interesting, I hadn't seen that before, thanks for sharing. It does look to me that in that case the chassis metal was pretty pitted by rust under the paint. I had a poly bush on mine for over 30,000 miles with no problems, and have just (in the past few days, not yet driven it) mounted it solid - I also have mounted the diff crossmember solid and raised the diff to improve half shaft angles. As you know I drive my car regularly and hard - I'll certainly update if I have any problems as a result.

ignatz

You're welcome. Just imagining the stress on that component, I think if your car can do a wheelie, that's the place where the car gets lifted up. I could be wrong but it seems to me the way it would have to be.

Metalhead140

Yes, agreed. And I'll admit that I looked at the brackets as I was bolting them together and briefly wondered about their sturdiness, but I couldn't recall any reports of them breaking. They can be beefed up easily enough, but probably not without making access in an already tight area ​​​​worse. A bracket that braces under that crossmember (similar to some old anti-tramp brackets I've seen on here) might be the best way to go if it turns out to be a problem.

corvettedave383

its all very interesting,

so if everything is solid mounted - where does all that movement energy go? does it move strain on the propshaft, diff input bearing/seal and brackets holding diff in place?

why did gm design everything to be held in place by a rubber bushes? mainly for driver comfort i take it? or ??

gkull

When you install solid motor mounts the motor at idle causes the nose body to slightly rock back and forth. Under power it TQ's the body over. When you solid mount everything in the rear like I did. When I had an automatic tranny the rear would squat when you put the car in gear with your foot on the brake. Under power the rear really squatted like when you take off on as the last yellow comes on during drag racing. To counter act all these bending forces I had a roll cage installed , went to 650 Pound QA-1 coil overs, and rear springs of over 500 pounds.

The person in the other post who ripped the differential snubber through the cross member mounting point had a horribly rust pitted thin frame.


See how they cut a slot for the rear mounting bolt? I just have a different bolt hole position and a thin aluminum bushing to get the up angle on the pinion. Just simple welding and drilling.

ignatz

Given the motor you have up front, I would say that is more than interesting. That "movement energy" is really torque, lots of it in your case, that eventually gets applied to a weld somewhere. And it is all the same amount once what ever bushings are in place get compressed. All the rubber does is take out the rate at which the torque is applied.

corvettedave383

ahh interesting stuff

yeah got the rollcage, full one rear and front, got the 650 Pound QA-1 coil overs, and rear spring of over 500 pound, all ticked

what is the actually benefit to soild mounts in the rear? just to stop all that twisting movement on diff, therefore leading to something breaking i take it?

corvettedave383

ahh good point, same torque but just slows it down a fraction

Metalhead140

Transfers that twisting motion more directly/effectively to the tyre. Should more or less eliminate any tramp - tramp theoretically should not be an issue with IRS cars, but often is due to compliant diff mounts. Also, as most of the rear suspension is mounted off the diff, reduces the amount that the suspension mounts are moving around, hopefully improving handling and stability. And it should help a small amount to stiffen the chassis, by making the crossmember and diff stressed parts of the chassis. Generally I think the main reason for soft mounts is to reduce NVH (noise, vibration, harshness), but I think our rubber mounted body's (later c3s like you and I have) tend to isolate us from that anyway. While that means the comfort impact is fairly negligible, it may still tend to put more stress on parts and tend to rattle fasteners etc loose if they're not ideal (in condition/torque/locking etc) - and puts some of the stresses that may have been absorbed (if not in magnitude, in harshness/suddenness) by the rubber directly into the chassis/diff housing/crossmember. I already have a solidly mounted engine and have no regrets about doing that.

corvettedave383

Still trying to decide what to do here, biggest issue iam having, is measuing the correct diff angle, i was thinking about maybe measuring off theSmart Struts, seems like a uniform bracket, can some confirm if the angle at the yoke is the same as the smart struts bracket?? or could i measure from the front of diff, where the front diff seal is , i can get a flat metal bar in there??

gkull

I used the diff case casting to put my digital level..... See how it is on the center of the front pinion?

squared

I used the same location. If you have an Android phone, you can install an angle finder app that works too. I don't use it to measure raw angle, but rather to compare angle of the diff and the transmission.

corvettedave383

ive still got propshaft on and its right pain to take it off, ive measured at the front of diff, on the front seal or yoke seal and off my smart strut brace and get the same reading - using a angle finder on my phone and using the tremec app aswell, ive decided to bolt the diff carrier hard to the vette chassis

ive got 1.7 degree downward angle on engine/gearbox and propshaft is going up by 0.8 of a degree and diff is saying its going up by 0.7 degree - the tremec app says thats me at a 1.5 degree working angle, which is all green in there app, good to go - anyone else bolted there diff carrier hard to chassis, what angle were you getting on diff?