4'' Lift Excessive Pinion Angle?

[MAX89K5]

Well I just got off the phone with Kert. He has a good condition used shaft and is giving me a deal on it! Ill have to have it shortened and rebalanced, but the local driveline shop quoted me $80 bucks for that. Im so ready for no vibes! Thanks for all the help y'all.

 

[eel757]

good you got it figured out i was gunna say just put a 2 in add a leaf in the back and see what happens mine and my buddies ended up at the right angels

 

[MAX89K5]

Got my CV shaft installed today after having it shortened. No more vibes! I'm tickled pink for it to drive like stock again. Thanks for everyone's input!

 

[MAX89K5]

Well guys I think I spoke too soon. After driving the Blazer more over the last few days I am still getting a vibe from 50+ and is accompanied by a deep hum, almost like mud tires. Gets progressively worse under throttle. The shaft has a new rear joint, the CV joints are original to the shaft, but they are smooth and tight. The driveline shop said it was a straight, tight shaft and CV.

My driveshaft angle is 16° and the pinion angle is 14°. Are these angles tolerable for a CV shaft?

Another concern I have is the slip yoke on the shaft only measures to 5.5" long, and is only splined for 4" of that, my total spline engagement with the output shaft is 3". Could this cause my issue or am I over thinking? A brand new tailshaft housing and bushing was installed whenever I was chasing a leak when I first bought the Blazer, so there is zero play there.

Should I bother with a 2° pinion shim to bring my pinion up, or buy a longer slip yoke (7") and replace CV u joints first?

Thank You all for your input!

 

[Mastiff]

I had a mild pulsating vibration at high speed in my Blazer for years. It might still be there with my new setup but I haven't been that fast yet. I never did find it, but I don't know if it hurt anything either. I think the big cavernous back of a K5 can magnify any resonance.

In any case, 2 degrees is perfect from all I've read. The pinion kicks up a little under acceleration, so starting a little down is what people go for. I'm not sure on the spline engagement. Good luck.

 

[MAX89K5]

It is pulsating for sure. Its just so annoying because I like to have everything just right, yet the Blazer is 25 years old.... lmao

 

[Mastiff]

It is pulsating for sure. Its just so annoying because I like to have everything just right, yet the Blazer is 25 years old.... lmao

I know. I spent a ton of money trying to run down that vibration. Now that I'm thinking about it, one big contributor was that my tailpipe mount was not isolated well from the body. The pipes resonated into the cab and made the vibration. Odds are against it, but you might check that the rubber isolators are all good.

 

[496truck]

It is pulsating for sure. Its just so annoying because I like to have everything just right, yet the Blazer is 25 years old.... lmao

You say "pulsating". A driveshaft vibe would typically be heard as a "buzz". When I hear pulsate, I think more of a slower shake.... wump wump wump wump wump wumpwumpwumpwmpwmpwmp as speed increases. If you can physically feel it shaking and can kinda keep a beat to it, it's more than likely a tire issue. Try rotating the tires front to back and see if anything changes.

 

[MAX89K5]

Its is most certainly a buzz type sound and when I say pulsating i mean it almost sounds like a exhaust drone that comes in and out. The tires are like new and had no issue before lift. Im grasping at straws here, my angles should be perfect according to the experts (pinion 2* down). All I can come up with is the slip yoke not engaging enough and causing my vibe...

 

[496truck]

So, wheels chocked, trans in N (no rotational load on the driveshaft), grab the slip yoke and try to wiggle it. Any movement? If so, how much?

If the shaft shop said it was a good CV I would expect that it is. But, my truck had similar symptoms. It eventually got really bad. Brought the shaft into my local shaft shop, the place that made it. They even said it felt good and tight but suggested a new CV ball rebuild kit with a longer spring for more tension. It was easy enough to do at home as long as you can do u-joints. The kit was cheap too. May be worth a shot if you don't know the history of your CV.

 

[MAX89K5]

Zero slack anywhere.. I am going to disassemble the cv and see if there is anything obvious.

 

[MAX89K5]

Dafuq?

Well I believe I have found my problem. Of course I discovered this after I had the shaft shortened... I went to replace the CV u joints and found that the socket that the ball rides in inside the CV joint is busted off the yoke. The welds are all broken and it is pressed in as well; which is why the shaft runs true (and is tight) until torsional forces are applied, like as if it were in the truck and under throttle. Which is where it vibrates most. I have emailed Kert and hopefully we can come up with something. I am going to have way too much money in a used shaft now that I have to buy a new slip yoke...

 

[496truck]

That happened to me when I took mine apart. I cleaned it up and tack welded it back in, good to go. Completely forgot about that till I saw your pic.

That was it, though. Once I got it all back together with the ball and spring rebuild kit it was nice and smooth.

 

[MAX89K5]

This one has been busted for a while. The surface where it was welded is rusted so it was nothing I did in disassembly. I have been leary of this slip yoke because it is shorter than most, and it makes my transfer case leak, so I'll just replace it.