Vibrations at Highway Speeds?

Hello Everyone,

 I own a 1984 Chevrolet K5 Blazer with a 5.0L 305cid, TH700R4, NP208, Dana 44 front and 12bolt rear with 3:73 gears and open diffs. I am looking at adding a Rough Coutry 4in. lift with American Racing 15x10 Bajas with 33x12.50-15 BFGoodrich All Terrain T/As.
 My concern is will there be any vibrations or "humming" from the driveline due to the different pinion angles? My Blazer sees alot of highway use with moderate 4wheeling and I like the fact that it drives without any vibrations. I have friends with other lifted trucks of various heights and some vibrate and others are smooth. Do any of you out there have a truck with a similar set up? How do you like it?
 Thank you and I'd appreciate any advice you all could give me.  

ive got a 78 blazer similar to your i swapped in the 700r4 and np 208 and i have a 4 inc rancho lift, as far as suspension or driveline vibrations i have none, you get vibrations if the angles of driveshaft are too steep so i got a t case drop which drops t case and front and rear driveshafts about an 1 or 2 inc and corrects the angles, im happy with it even though it reduces some ground clearence but i have plenty with 35 inc tires, your all terrain tires shouln't make a noticeble hum, i ve had 3 different sets of all terrains and none of them bothered me, if you going to put the 33s on i would gear the axles down to 4:10 or 4:56.  Another option instead of t case drop would be cv joints on your axles as cv joints can tolerate extreme angles but thats a more expensive route, anyways i wouln't lock the rear axle if you going to wheel hard cuz i broke my 12 bolt the 1st trip out to glamis sand dunes so i swapped in a 14 bolt one tone axle in its place, so have fun with the truck  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

Hey thank you very much.
Was your t-case drop part of your Rancho kit or can it be purchased separately? If so where can I buy one? I had planned on eventualy re-gearing it to a 4:10 ratio after the lift and wheels were installed. Due to the large amounts of snowfall where I live I had wanted to put Detroit Tru-Tracs front and rear due to their highway friendly manners and great reviews in the snow. Would this be a good idea for the Dana 44 and 12Bolt?
 Also did you reinforce your frame at the steering box? I have heard that is a common place for our trucks to break. Thanks again.  

with the 33's and the 700r4 4.88 gears would be alot better. 2261rpm @65

you can just use some tube stock and drill the holes for the drop.
the frames are weak there, if its not abused dont worry about it, though periodicly retighten the bolts.  
---------------------------

see me at robsoffroad.com

Before I would drop Tcase to reduce angle and clearance I would have a drive shaft shop install CV's on drive shafts and there will be no vibrations.  

Thanks guys for all your help. I'll keep you all posted on my progress and I'll post some pics soon  

no i havn't reinforced frame around steering box but it is my priority, i havn't had time yet, the t case drop kit i bought was from superlift and i came with some cool looking spacerers and grade 8 hardware, but as previously mentioned you can make your own spacer with some tube stock and find some good bolts, make sure you put on locking washer and nuts and put some loctite on the treads if you wheel hard and fast cuz mine rattled loose on my trip to glamis, i guess hitting the bumps at 55 mph isn't nice to bolts. As for gearing if your only running 33s then i say go with 4:56 rather then 4:10  Running trutracs should be fine as thier only limited slips, but ive had no experivce in snow so i can't comment on how they work in snow  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

Thanks..again for all the advice. I am looking foward to the transformation of my Blazer. I have seen kits for the frame re-inforcements. My dad and my brother are both licensed comercial welders and they told me that they could make the braces for me. What do you think is better to have a custom kit made or to buy the kit from a manufacturer?  

I would replace those gears in axle with at least some 4.56's if you want tranny to last. 3.73 x 305 engine times 33's x K5 = slug like performance at times (OD has got to be next to worthless) and a lot of time on converter stall or down shifting.  

yeah gear the axles as soon as possible, but about the frame, if your dad or bro can make one for you that would be good cuz im gussing it'll be cheaper but the premade one like the one from offroaddesign is nice becuase its almost bolt on and it triangluates frame mounting points thus sharing steering load with frame and crossmember.  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

Cool thoughts people. I appreciate the help. I am sure I'll have more questions as the project progresses. Keep ya posted.