Pinon angle calculation

[El_Capitan]

I guess ill bust out the angle guage again.. I doubt its in the rear end though. Maybe a bent pinion flange I'll have check that..

[snoranger]

Originally Posted by El_Capitan

It's a first gen SWB. So no carrier bearing, It has a double cardan rear shaft,

Originally Posted by kcm1582

Yup, I assumed it was a single u-joint shaft.

I read his post instead of assuming.

[El_Capitan]

Originally Posted by snoranger

Nope... Not on a double cardan (DC from now on) shaft. Everything shown above is 100% correct for a driveshaft with a single U-joint on each end, but a DC is a whole new ballgame.

With a DC shaft you want the rear pinion to point directly at the output of the T-case.

I swear I've tried that too.. I'm starting to believe it's just my luck lol

[snoranger]

Driveline vibrations usually get worse with higher speeds. Its very rare that they come and go within a small rpm window.

[El_Capitan]

Well that's awesome leave it to me to have the weird one.. ya it starts around 40 and by 55 its ok.. it's a droning type vib hard to explain. I really haven't driven it much faster than 65.. So we're wanting the pinon angle the same as the second u-joint of the DC? Correct?

[snoranger]

Basically, you want the single (rear) u-joint to have no angle, and on the double cardan (front) each u-joint will each see half of the total driveshaft angle.

[alwaysFlOoReD]

I had a 9" in a '68 Torino. When I changed in a used set of gears I got the same vibration your talking about. Later down the road, I talked to an [IIRC] instructor at a college that suggested that the ring and pinion were out of phase. It seems that there are certain teeth that will connect in one position but not another and if you happen to get the teeth meshed wrong you will get that drone.

Richard

[El_Capitan]

I hear you on that.. but I'll level with you this is the second set of gears I've put in this truck I did the first set and had the same issue.. Soo.. I. got another set and had them professionally installed thinking i did something wrong.. turns out it's exactly the same.. I wondering if the driveline itself is to blame. The thing is I really don't wanna spend a bunch a cash here, ( I already have) this is my daily and I want it to be right..

[4x4junkie]

Originally Posted by alwaysFlOoReD

I had a 9" in a '68 Torino. When I changed in a used set of gears I got the same vibration your talking about. Later down the road, I talked to an [IIRC] instructor at a college that suggested that the ring and pinion were out of phase. It seems that there are certain teeth that will connect in one position but not another and if you happen to get the teeth meshed wrong you will get that drone.

Richard

4.88 doesn't require any timing or phasing (IIRC, I think it's called a "hunting" gearset where every ring gear tooth will meet up with every pinion tooth at some point whereas a ratio like 3.50:1 or 4.00:1 is termed "non-hunting" and requires the mesh be phased).

As for the vibration, I've had some that come & go at different speeds, I wouldn't put it past a slightly out-of-balance shaft or a bent flange causing such a vibe.

[El_Capitan]

It does come and go at different speeds.. I'm wondering if its a u-joint phase issue. Like maybe the drive line wasn't assembled correctly.. Something like this..