Noise at 65mph + AWD

[gofalls]

Before I start tearing into it I thought I would get some advice and direction.

Van - 91 Astro AWD auto with no mods. Just purchased it.

Symptons - drives great up to 65mph. As soon as I hit 66+ it vibrates and growls. I then need to decelerate to about 50mph before it stops and I can return to 64mph and hold it at 64 with no problems. During the deceleration from 66+ to 50mph it vibrates and growls much more violently.

I thought maybe the ujoints would be sloppy buy I grabbed the drive shafts and they dont feel loose. Could it still be the ujoints or whatelse should I be looking at?

[LiftedAWDAstro]

Only real way to test/check the u-joints is to remove the driveshafts. A lot of times you will have a bound up joint so by eye and feel in the van you can't tell it's bad. When the rear driveshaft is out, check the axle pinion for any play or noise while spinning.

If nothing is found, pull the front driveshaft and take it for a test drive. Don't park on a hill as it will roll with the front removed. Again, check the pinion for play and noise.

[gofalls]

I pulled the front shaft out and drove it around with the noise. When the front shaft is out I can easily tell the joints are bad. Turns out they dont sell parts to repair it so instead my options were to buy a new shaft for $240. I should have it monday.

[v8famvan]

You are correct in that GM & the Aftermarket do not list u-joints for the front driveshaft.

I hope you have not got your new shaft quite yet. Take the shaft to a good driveshaft shop & have them replace the u-joints in it. A shop that knows its stuff will easily recognize the u-joints & be able to supply you with them or install them for you. Got this exact thing done for a customer a number of years ago for $45 installed.

[gofalls]

I took it in to the largest Ujoint and Shaft shop in Phoenix. The guy said he hasnt seen one in years and the only other shaft he has seen similar to it comes from a Bronco 2. The shop said they cant repair it and the only option was to make a new one. The new one with ujoints cost me $240.

[LiftedAWDAstro]

I had mine rebuilt at a Fleetpride. The only part they kept was the tube! Probably cost more than a new shaft but I did it in 2 stages trying to eliminate vibrations.

[shspvr]

You are correct in that GM & the Aftermarket do not list u-joints for the front driveshaft.

75 K10 4X4 front prop shaft u-joints

[v8famvan]

You are correct in that GM & the Aftermarket do not list u-joints for the front driveshaft.

75 K10 4X4 front prop shaft u-joints

I know the u-joints were a common one as the guy at the driveline shop immediately rattled off the number for them from memory, just not listed in a parts replacement book. Not at all suprised that they are the same as a 75 K10.

[Smiliesafari]

gofalls.......don't always take what the repair shops tell you at face value. Too many of them only want to take you for all they can. Case in point.......my hydro boost started to leak. I got a quote to replace it for $800.00. I took the faulty seal out of it and took it to a friend who operates a hydraulic shop. He got me the seal for $5.00. There's almost always a way to beat those who would try to steal your money.