Vibration in drivline! Help!

[joecls]

I have a 84 blazer with a fresh 406 small block and i used the transdapt mounts from jegs. i used the hole that makes the motor higher in the vehicle because the instructions said that no modifications were necesary other than beating the firewall lip and some at the back for dist.. so any way, now i have a vibration at about 3000 rpm and up and its coming fromt the drive shaft. Would moving the mount hole to the top hole(moving the engine lower in the truck) help any? any info would be appreciated

thanks, joe, lafayette , georgia

[Fergusonic]

I would say lowering it is worth a try as the pinion angle may be too severe. But also consider bad U-joint (did you use the old ones?), Driveshaft out of balance, (did you drop it during installation?) Wheels/tires threw a balance weight during one of your burnouts (now, don\'t tell us you didn\'t do a couple!)

[xeniadrums]

is the vibration right before your truck shifts?

[alz]

If its not ujoints and pinion angle( drive shafts straight ?) Does it vibrate at 3000 in neutral and park,if so look at your flywheel, 350s and 400s take different ones, one engine is interally balanced and the other externally

[mzoomora]

Different front balancer also. They bolt in place of each-other, but 350 is internal balance, 400 is external.

[joecls]

i used the stock 400 balancer and flywheel on this one even had them spun balanced, no the vibration is not in the motor in park or neutral. Does anyone know the proper driveline angle for the v8 apps.?Thanks again for the replies.

[mzoomora]

Is it 3000 rpm in every gear, or 3000 rpm in top gear, which would be a given speed. If it is strictly rpm, meaning in every gear, then it is the engine or trans, possibly the pilot bearing if it is stick. If it is speed related it could be the trans also, but also driveline or rearend. There is no real preset pinion angle, so long as they are a few degrees from parellell.

[riotpolice75]

i went thru this about 3 months ago. it would vibrate something fierce at like 80 mph. turned out to be my pilot bearing one time and the driveshaft being corkscrewed on another occasion. a quick way to tell if its a driveshaft is to put it up in the air and run it in order to try and see the vibration while everything is moving. this is how we found that it was my driveshaft, it was so bent you coulda damn near jumped rope with it. then to double check that the rest of the motor/trans was balanced we pulled the driveshaft and ran it, it was smooth w/o the driveshaft on it. this method worked pretty well for me so good luck if you want to try it.







smith.



p.s. if you do end up replacin some u joints get the heavy duty ones as some cheap insurance. also dont run it too long w/o the driveshaft(s) on it. it pisses tranny fluid all over the place.

[joecls]

yeah, i have the vibration all through the gears and at any speed, but it shows up at 2500 to 3000 and never quits, its pulses, if you will, the vibrations. I have heard if the driveline angle is not correct , it will cause a vibration but was wondering if anyone had this problem with the engine placement. By the way it is a turbo 350, with shift kit and performance clutches and planetary.Any MORE info is apprecieated.

[Cliff]

The driveshaft may be straight. But your pinion angle may be off check the actual angle of the differental compared to the crank shaft. That will tell you your pinion angle.





Cliff

[joecls]

okay, i can do that , thanks, does anyone use the slotted hole in the mount ?

[Knanthrup]

Could be a couple of things. Of course balancing could be one... maybe a weight fell off when you had it pulled. Another thing could be length... does it fit well like before or is it short or long? I know that when my driveshaft was too short it would vibrate because it didn\'t seat in all the way.

[mzoomora]

Maybe its just me, but usually a driveline vibration is speed related only, and he said his is rpm related. I would think that it is in the trans or further forward. The driveshaft spins according to vehicle speed, so if it were in the driveshaft it would be at say 50mph and up, not 2500rpm and up in every gear, that would be 3 different vehicle speeds.

[Knanthrup]

On 2003-12-11 19:10, mzoomora wrote:

Maybe its just me, but usually a driveline vibration is speed related only, and he said his is rpm related. I would think that it is in the trans or further forward. The driveshaft spins according to vehicle speed, so if it were in the driveshaft it would be at say 50mph and up, not 2500rpm and up in every gear, that would be 3 different vehicle speeds.



That\'s a very good point I didn\'t even think about. 3000rpm in each gear will be spinning the driveline at different speeds each time... I think it may be time to look for a different problem..

[joecls]

the vibration is definetly worse at a final 3rd gear point, somewhere around the 55 to 60 mph mark.thats when it pulsates, you know off and on kinda. thanks for all the posts, guys

[IceQueen]

I used to have a v8 in a corvette that did this because it wasn\'t properly broken in on that motor it always happened at 2K rpm and never happened in park/neutral. took me a while to find it but after I replaced the piston rings and re-honed the cyclinder walls and broke in the new rings correctly it was gone.



Just a thought.

[mzoomora]

You said before that you had your stock 400 balancer and flywheel spin balanced, and I dont think you can spin balance a 400sb balancer or flexplate. They have external weight added that would make them intentionally off balance, some aftermarket balancers even come with a removable weight that you can add or remove if it is a 383/400. If you had your flexplate balanced, they may have inadvertantly removed that weight not knowing that it was for an externally balanced engine.

[joecls]

well on the balancer thing, by spin balancing , i mean the balance them again. after a while 400 balancers and flywheels get off balance from wear and tear. they didn\'t remove any weights. all they did was drilled in the weight to make it true again. so no dice there i dont think. the engine is balanced perfectly. i started this engine with no problem in vibration just when your going down the road you feel a vibration that feels like its coming from the back floorboard of the vehicle. so what now? lol.... thanks guys for the replies. maybe we\'ll hit on something soon, cause its worrying me terrible!

[spacecadet]

I\'d suggest checking tyhe ujoints again. They may feel just fine - shakeing them on the truck but very possible they may be bad. Look for rust colored powder @ joint boots. That will indicate a rusted & possible seizing joint.

Then reove shaft from trruck and manualy move each joint to check for any binding.

[FastBikesRule]

IceQueen - How was the motor incorrectly brooken in? This has me curious. I never heard of a motor vibrating from not being broken in properly.

[alz]

Put your truck up on a hoist( one that can put the wheels in the air as well ) and try to duplicate the vibtation, itll be easier to locate or possibly see, in this situation. Have a listen and get rid of the geuss work. This could be so many things , Tail shaft bushing, shafts ect... Hopefully this will help ya

[joecls]

Hey thanks , i never thought of putting on a lift. Like i said before, i have built many hot rods in my day, (somewhere around 12) but never a s10 or blazer sbc combonation. And like i said , i have fixed vibrations before, but with this hybrid, i didn\'t want to second guess and knew that you guys are the pros, so i asked. Well, i will update you all, and tell you what i find. thanks, joe