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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: blakefehrn on March 24, 2014, 09:35:38 pm

Title: Broken Driveshaft and rearend pinion gear.
Post by: blakefehrn on March 24, 2014, 09:35:38 pm

Hi I'm new to the forum. I read them a lot mainly for knowledge. Now I'm at the point where I cant find any answers for my problem. I bought my truck about a year ago and have been trying to fix it up ever since. The truck is a 84 GMC K1500 4x4. I'm limited on my knowledge since this is my first real project.

So my problem is I broke the drive shaft and the whole rear end pinion gear off. I was test driving my truck after fixing a bad wheel bearing and brake caliper. So I was taking it for a cruise on the freeway and at about 55 I felt a pretty bad vibration. While I was trying to determine if it was tire vibration from my swampers or something else. So I'm assuming something else now lol.

So my real question is what would cause this vibration and this damage? The transfer case still seems to be working fine. In two wheel drive the shaft spins as normal. In 4 wheel i can go in reverse but in drive the rear end locks up and I drag the tires.

Thanks for the feedback.

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: Captkaos on March 24, 2014, 09:43:00 pm

Are the front and rear axles original to the truck?  Do the gear ratios match?  What transfer case is in it?
Is the driveshaft and pinion broken now or fixed?

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: pholliday1 on March 24, 2014, 09:49:48 pm

This truck may have a leaky pinion seal and they never properly torqued the pinion nut and it backed off.

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: blakefehrn on March 24, 2014, 09:53:02 pm

I believe they are aftermarket since its got a 208 transfer case married to a 700r4. The original transmission was supposed to be TH350. I dunno about the ratios. No the drive shaft and pinion gear are not fixed.

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: blakefehrn on March 24, 2014, 09:56:42 pm

Is that a leak i would see under the rearend? So I assume that would cause the vibration? Is there any way to tell if the rearend can be fixed or is it best just to replace the whole rear end? It will roll backward but locks up going forward.

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: Captkaos on March 24, 2014, 10:13:22 pm

Does the pinion move when going from D to R?  If so you have to pull it apart to see if it can be fixed.
Is the nut loose?

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: blakefehrn on March 24, 2014, 10:21:01 pm

There is no pinion anymore. The driveshaft is broken off along with the pinion. I can see inside the back of the rearend where the pinion should be.

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: Captkaos on March 24, 2014, 10:27:00 pm

It won't move because it is broken.  The more you try to drive it the more it is going to beat the insides up.  You will HAVE to get a new gear and pinon set, IF the carrier is ok.

Title: Re: Broken Driveshaft and rearend pinion gear.
Post by: Irish_Alley on March 26, 2014, 12:39:13 am

it might be cheaper and easier (with limited mechanical tools) to get a used set from the junkyard