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84 3/4 ton chevy, i get a horrible shake the faster i go

3K views 17 replies 10 participants last post by  BIG MUDDN 
#1 ·
okay, so i have a rlly bad shake in my truck, its an 84 3/4 ton with a newly rebuilt vortec 350. i was wondering if one of the reasons for my shaking could be that, i noticed there are 2 bolts missing out of my tranny, where my bell housing connects to the rest of my tranny. and also having about a 3 second delay when i stomp the pedal to the floor. y is that? plz help me.
 
#3 ·
Hi :welcome:
Welcome to Hotrodders.com Glad to have you with us

By a really bad shake do you mean vibration? or shaking as if a couple cylinders are missing?
As for the missing tranny bolts. I'd say there having no effect on vibrations or shaking, but I'd get two in there asap. Since you didn't know the bolts were missing, I assume someone else did the rebuild & insulation. makes you wonder what else wasn't don correctly.
Rich
 
#4 ·
okay, its vibrating like horribly, but all cylinders are firing. all thats fine, i do need to replace one wire though, i just noticed it melted to my header. but has been shaking before that, umm. yeah, that delay is pissn me off. and pretty much everything on the motor is new. new gaskets, carb., distributor. i just replaced all the plugs, but, like i said. i gotta get a new wire.
 
#6 ·
BIG MUDDN said:
oh and i bought new u joints and were gunna replace them but was told mine were fine. so i took them back to auto zone.
get a second opinion

did they check all 6 of them? front axle joints are common to use up when your big muddn.

also make sure its in neutral with a wheel chocked verry common to check them in park or gear, and it holds them together.

look for a rust colored dust around the joint we call this death dust.

how about a bit more info too

axles-
tcase-
trans-
 
#8 ·
no they didnt check all 6, only the back ones. ummm, oh and idk about the t- case but just sent it in to get rebuilt. umm i looked all over the tranny and nothing. i cant figure out what exact type it is, but its a granny 4 speed. umm oh and the axels and everything besides a 2 0r 3 inch lift is stock. do u think my tires would cause such a severe vibration? and how do i fix the delay? could that be my fuel pump, i have an electric one i could put on there.
 
#9 ·
no the fan blade didnt break off, and yes the firing order is correct, 1 8 4 3 6 5 7 2. and i changed all the plugs and need to change one wire for sure, but going to change all anyways, couldnt hurt. and it shakes when i get about 50 or 55 mph. the faster i go the more shake, it vibrates so bad it gets loud and cant hear anything.
 
#10 ·
123pugsy said:
Is it shaking under acceleration, at coast , at coast in neutral?
This is always a very important question that will narrow down where the vibration can be.

For example my 89 grand am would shake me so hard my vision would blur and I bit my own tongue a few times, but only between 72 & 76 mph, and had a lesser but very similar vibration around 35-40mph. Happened no matter what gear it was in, weather i was on the gas, cruising steady speed or coasting down.

The car had an out of round wheel in the rear which at certain speeds matched the "frequency" required to make the entire car vibrate as a unit, instead of just making a lot of road noise.
 
#11 ·
You may want to check your tires to see if you have broken belts. I use to do the four wheeling thing back in the 80s and busted the belts on a set of Michelens with only 18,000 mi. on them. It took a front end man to figure it out which took him about 10 sec. when he stood in front of it while I drove toward him and he said it was duck walking,thats when I learned a lesson on vibration.
 
#15 ·
Start with the simple stuff, mud in the wheels? Lots of those trucks need a shimmy shock or stabilizer, get one if you don't have it. Spin the tires and look for a lump or separation. Oh, and fix the stuff you already see wrong. You can't say an engine is running right if you have a plug wire melted to the header.
I recently had my van foul a plug and it sounded pretty normal but when the converter locked up it shook like a dog passing razor blades.
Who would tell you your u-joints are ok and not even look at all of them. How did they determine they were ok?
The hesitation could be a lot of things, what were you messing with just before it started doing that?
 
#17 ·
I think you have a couple problems. 1. A tuning issue and 2. bad tires, wheels, or U-joints. Its sometimes hard to tell if a U joint is bad without pulling the driveshaft. I had a u-joint go bad in my old 78 suburban and no matter what I did i couldn't get any slop in the driveshaft indicating a bad u-joint. Once I pulled the shaft (to replace the carrier bearing which I thought was the problem) It became very obvious that the middle u-joint was trash.

As for the delay in acceleration i think the timing is off or the accelerator pump in the carb is not working.
 
#18 ·
ok, ill check. i already had to pull the drive shaft, since i took out my tansfer case. also, my front drive shaft is not hooked up, it hasent been since i got it. so could that cause it to shake? :confused: since i cant drive it right now, ive been working on the inside, all i have left to do is install a new bright switch. so now im bored and cant start on the body rlly, until i can drive the truck to my buddys shop.
 
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