Launch drive-train shudder!

[76chev454]

I am perplexed.  Have had th400 tranny rebuilt with new converter, new u-joints and yoke on drive shaft but, I still get a shudder on start up and shifting between gears when accelerating hard.  76 496CID is putting out the power and can not figure my problem.  Would like suggestions on what else to troubleshoot.  Do not like the feeling when I accelerate too hard.  Rear axle is a 3:42 with posi-traction, if that is what they call it.  Send suggestions, please!

Professor of Interesting Stuff!

[roundedline]

Have you checked the engine mounts, tranny mount or the input on the rearend?

BTW, what kind of truck are you working on?

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[Blazin]

Is the drive shaft out of balance, bent, or twisted?

[76chev454]

I have a 1976 C10 Stepside HD truck that came with 454CID and TH400.  Engine is bored 60 over.  Roller lifters.  RV cam.  Balanced crank.  Edelbrock RPM intake.  Holley 770cfm street avenger carb.  

Professor of Interesting Stuff!

[76chev454]

Drive shaft has been balanced.  Engine mounts are fairly new.  About 1 year old.  I checked them and they look fine.
Am considering ladder bars of some type to help hold rear down.  Engine has tremendous torque.  Thanks for replies.

Professor of Interesting Stuff!

[roundedline]

I guess I am confused, is this a shuddering of the drivetrain or rear axle wrap.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[76chev454]

Not sure where it is coming from in the drive train circuit.  I am confused some too.  Maybe I ought to take it to a drive train specialist.  Hard to find them in Naples, FL though.  If it were a Mercedes, it would not be hard to find help. ha  

Am going to attack the rear axle first.  I have the parts to build a similar system to CalTrac.  Will let you know if it helps my launch!  

Professor of Interesting Stuff!

[roundedline]

I know Cal Tracs work, let us know.  If it is axle wrap, (wheel hop) you can visibly see it if someone is outside the truck.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[DnStClr]

Sure sounds like a nice setup ya have there.
When you say the truck shudders upon start-up, do you mean it shakes when you START the truck? Or do you mean when you start to roll under heavy throttle? If it's the 1st description, could you have an engine problem, like the wrong spark plugs or a failing coil, especially if this shudder is more noticeable when you're pourin the power to it?
Doesn't sound like the tires or frame if it's not shuddering all the time...
 

[76chev454]

It only "shudders" when "launching" or taking off fast from a stoplight.  Please don't send police.  Does not do it when downshifting to pass or when I reach 30 or 35 mph.  If I do not accelerate fast, no shudder.  Have Mallory HEI and Taylor plug wires.  Wish it were just plugs.  Thanks for your input.

Professor of Interesting Stuff!

[DnStClr]

Here's a guy using the CalTracs syst- No hop..

[76chev454]

Look at the hood scoop on that Chevy!  Wow!  Must be a big blower.  Looks like his launch is a smokey one.

Professor of Interesting Stuff!

[1tonson]

have you determined the shudder problem would really like to know!

[ccb]

I know what hes talking about its axle rap. Needs traction bars.
He is launch from a stand still. and gets a shutter from acceleration off the line.  And you can see that if someone know what to look for which is wheel hope which was already mention.

Craig  

[1tonson]

my 83'k-30 has this shudder badly when your hard on the gas after the clutch is engaged(let out)2nd is terrible.and third is just noticeable,its not (wheel hop)with as much weight as i carry on the gooseneck.you can make it not do it by treating her gentle (easy on the power)but it will rattle your fillings loose its so bad,this truck has a 94'smb and i thought maybe the external or internal balance flywheel maybe cause, axle wrap is easly cured with traction bars. i love 'em rocks dont.