U joint help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gman · 10-30-2003, 05:47 PM

Have a god awful clunk noise when releasing the clutch. If I release it extremely slow, i can prevent it. But just drivng it normally, it sounds like hell.......like its going to break. I'm assuming its u-joints but I'm not sure. How do I diagnose where the problem is? The u-joints at the back differential, at the front of the transfer case and the rear of the tranny all have zerks on the inside of the joint and are so cramped I can't get a grease nipple on them. Are the non greaseable kind the way to go if the u-joints need replacing? Any wisdom appreciated. Thanks!

Southpa · 10-30-2003, 06:08 PM

Usually the symptom for a bad u-joint is excessive vibration in the drivetrain while driving. Any of that happening at any particular speed on the highway? You could also check your rear end. Jack up the back of the truck and see how much play is in the wheels. Turn the rear wheel until you feel the gears mesh. If there is a lot of rotational travel distance then you have worn gears. Thats usually the "clunk" you feel/hear when putting it in gear. Its really noticeable when just starting up and the motor is at fast idle.

Well, waddya know! Post no. 2000! Do I get a prize?

gman · 10-30-2003, 06:14 PM

No, there is no vibration at all. Rides very smooth actually. Steering wanders a little bit but thats another question. I'll check the rearend by jacking it up like you said.

**Stocker** · 10-30-2003, 08:21 PM

Another characteristic of failing u-joints is a metallic "ping" echoing through the driveshaft when you first apply power.

Greasing u-joints is easy - buy or build a needle-point adapter.

71GMC_3/4T · 10-30-2003, 09:50 PM

Could also be the bushings in the rear suspension.
If you have someone you trust very well, have them shift from first to reverse with the front wheels blocked on both sides to keep it from rolling. Look at the ends of the leaf springs, or at the end of the trailing arm up by the cab, whichever you have. If you see movement that coincides with the noise, you've found it.
You might want to pop the hood and check the motor mounts if you don't spot something underneath.
Hope you find it!

10-30-2003, 05:47 PM	#1
gman Registered User Join Date: Nov 2000 Location: Ogden, Utah Posts: 290	U joint help Have a god awful clunk noise when releasing the clutch. If I release it extremely slow, i can prevent it. But just drivng it normally, it sounds like hell.......like its going to break. I'm assuming its u-joints but I'm not sure. How do I diagnose where the problem is? The u-joints at the back differential, at the front of the transfer case and the rear of the tranny all have zerks on the inside of the joint and are so cramped I can't get a grease nipple on them. Are the non greaseable kind the way to go if the u-joints need replacing? Any wisdom appreciated. Thanks! __________________ 72 Chevy SWB Custom Deluxe K10, 350/SM465, PS, PB, Fact. Air 2000 Harley...Wide Glide

10-30-2003, 06:08 PM	#2
Southpa Registered User Join Date: May 2000 Location: Victoria, BC, Canada Posts: 2,409	Usually the symptom for a bad u-joint is excessive vibration in the drivetrain while driving. Any of that happening at any particular speed on the highway? You could also check your rear end. Jack up the back of the truck and see how much play is in the wheels. Turn the rear wheel until you feel the gears mesh. If there is a lot of rotational travel distance then you have worn gears. Thats usually the "clunk" you feel/hear when putting it in gear. Its really noticeable when just starting up and the motor is at fast idle. Well, waddya know! Post no. 2000! Do I get a prize? __________________ 1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first.

10-30-2003, 06:14 PM	#3
gman Registered User Join Date: Nov 2000 Location: Ogden, Utah Posts: 290	No, there is no vibration at all. Rides very smooth actually. Steering wanders a little bit but thats another question. I'll check the rearend by jacking it up like you said. __________________ 72 Chevy SWB Custom Deluxe K10, 350/SM465, PS, PB, Fact. Air 2000 Harley...Wide Glide

10-30-2003, 08:21 PM	#4
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,728	Another characteristic of failing u-joints is a metallic "ping" echoing through the driveshaft when you first apply power. Greasing u-joints is easy - buy or build a needle-point adapter. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

10-30-2003, 09:50 PM	#5
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	Could also be the bushings in the rear suspension. If you have someone you trust very well, have them shift from first to reverse with the front wheels blocked on both sides to keep it from rolling. Look at the ends of the leaf springs, or at the end of the trailing arm up by the cab, whichever you have. If you see movement that coincides with the noise, you've found it. You might want to pop the hood and check the motor mounts if you don't spot something underneath. Hope you find it! __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO



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