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new member has driveline questions. help please!!!

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baker440ex

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hey everyone, i have a few questions about the driveline in my 89 blazer, hopefully someone can help. here's the info: i just got it on the road after it sitting for a long time, and i've been picking away at it for the last 6 months or so. one of the things i did was throw on some 33's and 3" lift blocks in the rear, to compensate for the sagging rear leafs. when i took it out and got it up past 35 or so there was a real bad vibration coming through the dash on acceleration. (this is in 2wD) when i let off the gas it would go away but vehicle would lose speed real fast. i had front tires balanced and also found 2 bad tie rod ends, which alleviated a little of the vibration but it is still very prominent. now there is also a vibration at low speeds, before coming to a stop and when taking off from a stop. the rear drive shaft does have some play in neutral at the rear end, and it almost seems like its got the wrong u joint in it, like it is a hair too small, the play is between the ujoint caps and the retaining clips on the yoke (not to be confused w. snap ring). not sure why this would be? i only drove it once before i added lift and tires but i do not remember it vibrating this bad. what my question is from here, is first, would the small amount of drive shaft play be causing this much vibration, and second, would the 3" blocks in the rear throw the drive line angle off enough to vibrate this bad? (someone on here said no if its under 4"s of lift??) i checked trans. and transfer case mounts and they appear to be fine. is there anything else i should be looking for? sorry for long post, i'm new in diagnosing 4x4 components, and trying to save money if at all possible. found a lot of related posts but still looking for insight. thanks in advance!
 
3" of lift is certainly enough to cause vibration. If the u joint is questionable replace it. You could have a bad pinion bearing or a bad wheel bearing. Could also be an out of balance drive shaft. Search on here for how to measure your drive shaft angles. Start with that.
 
thank you for quick response. looked for how to on measuring drive line angle. i haven't measured it yet but if this is the case (and now i'm thinking it is just by looking at it) what would be the next step to alleviating the vibration, could i get away with just lowering the transfer case? what would be the cheapest way to tackle this? after installing the blocks the yolk coming out of the transfer case now sticks out an extra few inches. (don't know if its a drive shaft length issue or if that only pertains to bigger lifts) just looking at the drive shaft with the naked eye it looks like there is too much of an angle, it just seems strange because i had almost identical truck ('90 gmc 4x4 reg cab short box) and installed 3" blocks in the back and never had a vibration issue. does the "rake" stance possibly make the angle worse? like i mentioned earlier i was only really trying to take the sag out of the back of the vehicle, and never considered it altering the d.s. angle. so, in a nutshell, is the t-case drop the fix if my angles are more than 1 degree apart?
 
i know there are leaf shims available too - would i be able to achieve proper angle with just the t-case drop mod? you cant stack blocks with shims right?
 
Did you just use a straight block? The blocks that come in a lift kit are ground at an angle to help alleviate this problem.
 
yes straight blocks. i was unaware until now they offer tapered ones. (these are the same blocks i used in '90 s.b.)
 
so are the straight blocks my problem? or is it too hard to tell via description. does someone have a simple explanation on how to measure d.s. angle so i can confirm if this is my problem? wondering if it would be easier to pull the blocks back out.
 
I would say if all you did was lift the back of the Blazer with blocks, and the front is still stock, this is completely the cause of the vibrations. By raising the back without the front, the driveline angle is probably way too steep, basically the TC output is pointing up, while the rear end is probably angled slightly down. If you are trying to correct for sagging rear springs, consider going with a zero rate rather than the blocks.

I don't recommend lowering the TC, and you will find most on here agree with this. It creates other problems that you really don't want to deal with. The only other solution would be to get some 3" front springs installed, with steering correction, and see if the vibrations go away, but I am almost certain they will. Blocks create their own issues with axle wrap as well, which combined with a bad driveline angle could create a lot more vibrations.
 
I just finished my 3" lift and I had to install a 6deg rear shim and a t-case drop to get rid of the vibes. Theres no problem with lowering the t-case if its done right, only downside is loss of center ground clearance


google how to measure pinion angle, its real easy
 
i actually just got done taking the blocks out, and this seems to have been the problem, although i only went down the street and back. but the drive shaft was definitely at too much of an angle. i'm going to get an alignment later today and then i will take it up to speed. well she's saggin again but at least it doesn't feel like the motor is going to fall out anymore, thanks for the help everyone!
 
ok, that definitely did not take care of the shaking. i just went to the store, thought everything was fixed until i left, taking off from a dead stop it was clunking real bad. as i mentioned earlier i found some slack in the rear of the drive shaft, at the rear end (this is without the wheels off the ground) and it's like it's got the wrong size universal joint in it, because you can see the play is between the bearing caps and the clamps that hold the u joint on to the rear end yolk. so i'm thinking it's not necessarily a bad u joint but either it's the wrong one or the clamps are the wrong ones? i have a new neapco u joint here part number 2-3011 it looks like the same one that's in it now, i measured the caps on both u joints and they are the same size. do i have the wrong one? i know it's got a th350 but came factory with a 700r4 not sure if this would make a difference. someone please help, its cold outside!!! lol
 
The best way to measure the driveshaft angles is this.

Remove rear driveshaft, arrange yolks so so you can put an angle finder on them. Put an angle finder (you can find these at nearly any hardware store) on the yoke.

If its a non CV shaft (which I think it might be) the angles need to be opposite of each other. I.E. if your yolk on your t-case points down at 5* your pinion needs to point up 5*.

If you do this while your driveshaft is off, check the pinion yoke for play.

You say you have a TH 350 what t-case, 208 or 241.

If you like it with the blocks in put them back in. It can be solved just as easily with the blocks in or out. Might cost a bit more with the blocks in.

I also don't think that it would have sagged 3" mabey an inch or a bit more so you more than likely lifted it 2"
 
The u-joint is the problem, measure the width of the caps and the width of the cross and then measure what you believe to be the cross width and cap width of the yoke side.
 
You may also be dealing with worn centering tabs on the yoke. If the tabs don't hold the u-joint centered it is going to allow side to side play. Just something to look at while you have it out.
 
thanks guys i really appreciate all the help. doing u joint later today, i will let you know how that goes. when i get some money saved up i'm going to start piecing together a lift the right way.
 
props to lectric80 who hit the nail on the head. bad yolk. and the parts store did give me the right universal. course i dont have a spare yolk so it will be a couple days at least till i can see if that's all it was causing the vibes.
could the wore yolk be a result of the lift blocks? even only driving it probably 30 or so miles with the bad drive shaft angle, or was it most likely bad when i bought it? just wondering
 
Probably bad when you bought it, and I am glad you caught it now. Mine kicked out at about 65 miles an hour on the freeway, spit a cap out, and needed a great member of the brotherhood to come to my office at 11:30 PM with a spare joint and a welder. One thing about this site is that we truly are a brotherhood, and everyone helps out when they can.

One thing that might work, I just have never gotten around to putting it on, is some u-joint girdles. They replace your strap and provide a solid outside block on the u-joint. I have some, they are the right size, but I just haven't taken the time to install them since I have a set of 3/4 ton axles to swap in.

http://www.summitracing.com/parts/MOR-85800/

That should be the correct part assuming you have a stock 10 bolt rear. I hope one of the other members of the brotherhood will chime in and confirm that is correct.
 
thanks agian lectric for the insight, very helpful indeed. i will most likely get those blocks off summit. actually someone i was talking to here at work said that yoke could have worn out because of the straps either being lose or somehow warped. as for the new one i priced at about 80 bucks, and the rear seal in my transfer case has a small leak so i think i'll tackle all of that throughout the week, and hopefully with a stroke of luck i'll be good to go after this.
 
lectric80 said:
Probably bad when you bought it, and I am glad you caught it now. Mine kicked out at about 65 miles an hour on the freeway, spit a cap out, and needed a great member of the brotherhood to come to my office at 11:30 PM with a spare joint and a welder. One thing about this site is that we truly are a brotherhood, and everyone helps out when they can.

One thing that might work, I just have never gotten around to putting it on, is some u-joint girdles. They replace your strap and provide a solid outside block on the u-joint. I have some, they are the right size, but I just haven't taken the time to install them since I have a set of 3/4 ton axles to swap in.

http://www.summitracing.com/parts/MOR-85800/

That should be the correct part assuming you have a stock 10 bolt rear. I hope one of the other members of the brotherhood will chime in and confirm that is correct.
Click to expand...

oh man Im gonna get me some of those :thumb:
 
lectric80 said:
One thing that might work, I just have never gotten around to putting it on, is some u-joint girdles. They replace your strap and provide a solid outside block on the u-joint.
Click to expand...

Wow, this looks like a great product, but I'm wondering what they center on. Is it located precisely enough to compensate for worn centering tabs or is the only advantage greater strength? It certainly is cheaper than replacing a yoke.

mor-85800.jpg


Plus, looking at the hardware (bolts and nuts), it looks like it might be designed to replace a U-bolt and not a strap. But I don't see why it couldn't work either way.
 
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