Rear end problem
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Senior User
Joined: Feb 2004
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OK. I think I am close to solving this. Today I took both axles and the carrier out and ran the truck in 1st gear just driving the pinion gear in the housing. I could clearly see that the pinion gear was wobbling and not in a perfect circle as it should be. I removed the pinion gear and bearings and the bearings don't show any excesive wear and are not falling apart, therefore I am assuming that the pinion gear shaft somehow got bent by the previous owner. when I spin it by hand I cant see the wobble,(can't hold it still enough) but it was certainly there while the truck was running. Is there any way of checking the shaft to see if it is bent or if the bearings are messed up or if it is something else? Also, if it is bent, do I need to get both a ring and pinion or can I just get a pinion gear? Thanks again.
Cargo Master
Joined: Dec 2003
Posts: 2,735
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From: Sunny Florida
You will need a new gear set which includes both the pinion and ring gear. To check the pinion for run out you will need a few measuring tools to check correctly. Unless you have access to a machine shop and some measuring tools it may be difficult to check. Since you have it apart you may as well just rebuild the rear axle and then you know what tou have.
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OK. I put the ring and pinion gears out of my old rear end in this thing along with bearings and bearing races and it still does this. the pinion gear does not appear to have the out of round movement that the old one did. I admit I did not set up the ring and pinion the way I should, but use the same shims that were in it. I am just trying to troubleshoot. Anyway, I borrowed a drive shaft and it does the same thing. I have also changed both u-joints.
With the rear axle on jackstands any time that I accelerate or decelrate there is this violent shaking in the truck and also I can still see the driveshaft (regardless of which one I use) moving up and down a little.
I have replaced just about everything except the side gears in the rear end and just keep having this same problem. One thing I do notice is that my drive shaft doesn't appear to slide up into my tranny as far as it did before and there is some movement in it when I push up and down on it. Is this normal and could it be the cause of my problem?
With the rear axle on jackstands any time that I accelerate or decelrate there is this violent shaking in the truck and also I can still see the driveshaft (regardless of which one I use) moving up and down a little.
I have replaced just about everything except the side gears in the rear end and just keep having this same problem. One thing I do notice is that my drive shaft doesn't appear to slide up into my tranny as far as it did before and there is some movement in it when I push up and down on it. Is this normal and could it be the cause of my problem?
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It's the same transmission that was in it when it was 2wd and both the springs and trans. mount are OK. I did some measuring today and it looks as if the rearend is about 1" further back than the old one. I measured from a crossmember on both my good truck and the donor truck. Both rearends are 8.8's. the only differance is, that my old one was from a 2wd and the one I am having the problem with is from a 4wd. The only thing I can think of is that the stock spacer blocks on the 4wd rearend are making it further from the tranny to the rear end. Anyway, there is 1" of clean metal on slip yoke where it used to ride when it had the 2wd rear and if I shake the driveshaft there, it has a little up and down movement. If I slide it up where it used to be it seems a lot more solid. So now I'm not sure if this is the problem or the rearend and can't think of anything els to do to find out.
Cargo Master
Joined: Dec 2003
Posts: 2,735
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From: Sunny Florida
The slip yoke sounds like it sticking out to far for sure and i would bet this could cause a vibration. The yoke shouldn't have no more than an inch of clearence between it and the back of the trans.
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Thanks. It sounds like this could be it. I just wish I would have noticed it before replacing everything in the rear end. What I don't understand is why it would now be shortened from when it had the other rear end in it.
Cargo Master
Joined: Dec 2003
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From: Sunny Florida
I know on the 9 inch rear ends they have a few different length yokes so that may be the case with the 8.8 rear axle and on the 9 inch I think it is very common for the difference to be 1 inch.
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From: Hallettsville, Texas
How tall are the blocks? If you have play on the slip yoke it will definitely cause the shaking. Did you check your driveline angles? The reason the shaft appears shorter is because when you moved the rear axle down away from the springs, it does in fact lengthen the distance from the tranny to the pinion yoke. You will probably need to add to your driveshaft the amount of the distance from where it used to be. If there is one inch difference, you will need to make your driveshaft one inch longer than it is now. Have the shaft balanced after you have had it lengthened. If you don`t lengthen it, your truck will probably spit it out at full or partial droop not to mention the destruction that will be happening to your drivetrain. Good luck.
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It just has the stock blocks that come in a 4wd. The strange looking things that point toward the middle of the truck. I am just going to go ahead and put the transmission and transfer case in it, then I can use the drive shafts that came on the donor 4wd. If in fact this is the problem, I hope it helps someone else from making the same mistake. I guess you can't put a rear end and springs from a 4wd into a 2wd and still use the 2wd transmisison and drive shaft until you have time to complete the conversion. Thanks for all your help, I will put the transmission and transfer case in 1st chance I get and hope this fixes the problem.
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Update: I removed my t-18 2wd tranny and got ready to install the np435 and transfer case. As I inspected the clutch, I noticed thhat the pilot bearing had fallen apart. There were little needles from the bearing all over the place. I have replaced the bearing, clutch, and throwout bearing and have the 4wd stuff installed. I should have the rear driveshaft in today to where I can run it. Is it possible that the pilot bearing was my problem the whole time?