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Vibration after new gear install

midnitewarya

midnitewarya

Sounds like a problem for future me.
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I recently installed 4.56 gears in my 1991 K5 10 bolts. It was done professionaly at a Chevy dealership, and I am running 35's on the axles. Sine the install, there is a vibration that seem to come from around the transfer case when I let off the gas slightly. It occurs at speeds over 45 mph. The vibration goes away afer I let back on the gas. Also, at high speeds, there seems to be a new rythmic vibration coming from the back. I have an NP241 transfer. Has anyone else had this problem or know of it? I'm currently modifying my truck to run quieter and smoother for my newborn, and this is one of my big problems.

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Have your driveshaft balanced. It is spinning faster than it was before the gear swap and now the vibration which was once faint, is very obvious.
 
I thought I should add that the vibration also produces a rattling noise coming from what sounds like the transfer.
 
Easy question. With your lower gears, the driveshaft is spinning faster than it did before in order to run the same road speed. You may need to balance the driveshaft, but I think you should take a look at the angles on it first. You can go to the HAD website for detailed drawings of how your pinion angles should compliment each other....or you can just ask.
 
Concerning the vibration I would agree that it is probably the angle of your drive shaft. I wouldn't worry about reducing noise just for a newborn. Both of my kids were more relaxed and slept better in my noisy blazer than my wifes quiet car. :D
 
Like a couple of other guys said. Sound like classic driveline angle issues. Check your angles. Look for any slop in the splines, and inspect or replace the shaft Ujoints.
 
midnitewarya I have the exact same issues except I installed my own gears. So of course I am questioning the installation. I have played around with some dirveline angles but nothing seems to help. I went from a 3.08 to 4.56 so it makes some sense that it be a driveshaft issue but the sound is definitely coming from the front of the axle housing. Please post if you are able to remedy your problems.
 
midnitewarya said:
I'm currently modifying my truck to run quieter and smoother for my newborn, and this is one of my big problems.
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My son is 8 weeks old today, every time he gets in his carseat he falls asleep, our DD is my 85 3/4 ton which rides like a tank and is loud as hell, my son is asleep before he is even in the truck...I wouldnt even worry about noice.
 
if its comming from the front of the axle housing, it is possible that the pinion bearing preload is incorrect..not saying that this is what it is, but its somthing to look into..i work at a gear shop and from time to time have guys bring in their rigs that they did their own gears and have noise and the pinion bearing is shot, even though they only have a few hundred miles on it, because it wasn't set properly, worth looking into..and i've said it before and i'll say it again..BABY it for the 1st 500 miles to break it in, that means no romping on it, no spinning the tires, no towing, and actually for the fist 100 miles or so, you shouldn't go more than 30miles with out stoping to let it cool off..not saying that you didn't do this, but there are some who don't..
 
Thanks for the reply. It has less than a hundred miles on it (with no more than 20 a trip). The only issue is that it has done it from the start of the gear install. Like 20 miles. I haven't been hard on it at all. Got it up to highway speeds a couple of times. Used passing gear etc... Not sure how babied I should have been though. I did consider the pinion preload. We used a large breaker bar and only had a 20 inch pound torque wrench (click type at that). So it may be off. We opened it up this past weekend to tighten the backlash (long story but we didn't have a dial indicator so we set it up a little loose at first). I am sort of tried of dealing with it. I may take it to a gear shop and just pay the 200 for them to re-install them. Kinf of suck because of all teh time I have spent.
 
it might be worth it to have a shop look at it, i don't know how other shops are, but we do free inspections..and even refill the diff for free(thats how we keep them comming back, treat them like kings) lol..and as my boss says for babying it, drive it like an 80 year old man, who doesn't have the strength in his legs to push the gas peddel...you get the picture, nice and easy...and if the gear set or pinion preload is wrong, you can get noise just backing out of the shop, really doesn't take much to screw up a bearing if its not installed properly..

but even i don't always baby it, when i stuffed 5.29s in my ex girlfriends mustang gt(girl friend at the time) i backed it out of the garage, and then preceeded to smoke the tires all the way down the block........and yes i had to re gear it again lol..but 5.29s man! couldn't resist!lol:D
 
The only shop I called wanted 70 to take a look at it. If your shop os close to LR arkansas I will come see you.

That is funny. I went from a 3.08 and a messed up 200 hp 350 with 35s to 4.56 and a brand new 300+ hp 350 in about a two week span. I was probably over excited as well. I will try and call a few shops today to see what they charge to inspect. You would think that it would be cheaper because if they find somehing wrong they would get the work. But who knows.
 
yeah with all them new toys, its possible you got a little excited, when i smoked my ex's tires on her gt, i knew they were screwed half way through the burn out, i heard the gears screaming, but thought "oh well, gotta do them again" and kept on going down the block,luckly for me, because of where i work didn't cost me a penny to get another set of gears..and your right about the last part, thats why we do inspections for free, because odds are you will have us do the work...as for near little rock? hmm, i'm about oh 3 maybe 4 days away..i'm in northern califorina..about an hour Lake Tahoe and an hour from Sacramento..but hey my uncle lives in Paris Ar, say hi for me lol.
 
Babies love loud droning noises.My suburbans noisy wore out 35s put my 4month old daughter right to sleep.Our pediatrician says that the inside of the womb is as loud as if your newborn were sleeping next to a running vaccum cleaner.Sorry this doesn't help your gear noise problem but it may help convince the wife you are driving a baby sleep machine.
 
I was under the impression that the slower the driveline spinns the more likely you are to feel it vibrate. The faster it spinns the less likey you are to feel it vibrate. That is why they balance drivelines at slower than normal operating rpms.
 
So six years later I finally figured it out. It was the shaft. Put the new one in today and it's super dooper quiet.
 
And it took you only 6 years to find out? :haha::waytogo:

Lots of old timers on this thread. Sure miss some of them.
 
thatK30guy said:
And it took you only 6 years to find out? :haha::waytogo:

Lots of old timers on this thread. Sure miss some of them.
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Yeah, the kid finally got old enough to tell him what was wrong.....
 
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