60 impala shudder under power

[LMBRJQ 60]

Hi There Guys,
I havene had a look under at every thing yet as the weather is crud over here at the moment. Took the car for its first jaunt to a local guys place with a hoist so i could get the official inspection from the authorities under way. Every bush and bolt is new under the car as well as a new balanced drive shaft but i have a shudder under acceleration from a standing start until around 10-15 MPH then it go's away. when you are rolling and put the foot down the shudder is not there. not sure if diff alingment would do it (12bolt Pozi trac) has any one got any ideas of where to start???
Thanks in advance steve

 

[walkerheaders]

driveshaft angles? center support bearing? or more importantly, the rubber around it. nice car BTW

 

[LMBRJQ 60]

driveshaft angles? center support bearing? or more importantly, the rubber around it. nice car BTW

Thanks for that, i have a new centre support bearing in there but when i pulled the car apart the bushes in the trailing arms were shot. I re fitted the shims on the upper banana bar thinking this would be alright but it may be a mile out?
Steve

 

[409z28]

suggestion

Do you have the correct flywheel or flex plate.. Int or ext balance? cant remember which is correct

 

[mac1]

Check the rear shock upper mounts. I had the rubber bushing slide out from the shock housing and it made a similar sound. Took me a while to find it.
I like your car.

 

[Fathead Racing]

I re fitted the shims on the upper banana bar thinking this would be alright but it may be a mile out?
Steve[/QUOTE]

This is undoubtedly your problem, pinion angle is more than likely way out of spec.

 

[MRHP]

As Fatride said. Pinion angle and check driveshaft phase as well. Nice car.

 

[jim_ss409]

I agree with the other guys, bad driveline angles can give you the exact symptoms you described.

 

[LMBRJQ 60]

Thanks for all the advice guys. I hadnt really checked the angles of the rear end as i havent got the car fully assembled to determine final ride height yet (back springs are a bit wallowy) Will climb under her tonight and have a look.

409z28 it is a 454 with original flex plate etc on it

Mac 1 i put new shocks on her when did the chassis but will check when im under there tonight.

Thanks again, will keep you all posted

 

[tartan1]

Check your front body mounts...see if the rubber is missing...I had this same problem and it took me awhile to figure it out

 

[LMBRJQ 60]

Check your front body mounts...see if the rubber is missing...I had this same problem and it took me awhile to figure it out

Thanks for that, did a body off and put all new mounts under her, will re-check all bolts and bushes under the whole car though. Thanks
Steve

 

[sam 15]

LMBRJQ 60, did you get this figured out yet? Nothing more frustrating than something like this. You describe the problem as a shutter. If you couldn't use the word shutter, what other word could you use to describe it? In my experience a driveline/pinion angle is more of a vibration problem. What kind of electrical/fuel system are you running....i.e. stock for that year...newer FI w/ ECU or ECM....carb w/HEI? It's sometimes difficult, but have you determined appromimately where the "shutter" is emminating from, front of the car, mid section or back half. If it's a driveline problem and it's coming from the rear of the car (and it's not a vibration) my first thought is to check the rear end for proper gear set up. Also check to pinoin itself...mid section check the trans and converter and front check electrical/fuel delivery system. Sounds like you have already checked to make sure everything is tight/toqured under the car already. Lets us know what you find.

 

[LMBRJQ 60]

The shudder feels like i have got axel tramp or similar. Definately from rear end.
Havent jacked her up yet that is tonight as have a bad case of work hit me.
Not electrical, the fuel delivery etc i beleive is alright as when you are mobile and give it a boot ful the problem is not there so i am assuming thet from a standing start i am crouching the rear enough to take the pinion angle beyond where it is supposed to be and when it is mobile even with the power turned on it dosent crouch as much so the proble moesnt re appear?
Want to lower her a bit so may take rear springs out and set it all up at the ride height that i want. I think that the rear springs being originals and seem very soft may be adding to the problem.
your thoughts.

 

[petepedlar]

I have been watching this thread closely as my Impala does the same thing. Only in first gear..... I have a new drivesahft & steady bearing, new shocks & sway bar. When I installed the engine I had to lift it up about 3/8 of an inch..... and the new springs raised the front of the car...... shouldn't be enough to bother the driveline angles. I do have 3.08 gears & 700R4. I'm thinking it's the amount of torque going through the diff in first gear is making her roll up a bit to throw the driveline angles out..... maybe a combo of the engine being up a bit, front up a bit and the torque.

I'm sure mine is driveline angles.

Dave

 

[oldskydog]

Posi chatter? Sometimes adding more special posi lube cures it.

 

[62impala409]

Had exactly the same type of "shudder" when I put the 327 and TH350 into the '62 many years ago. All new parts. My column mounted shift lever would jump up and down when starting out. Checked the drive line angles with a protractor and found I needed to add one shim under the rear tranny mount. Problem solved!!!!! The drive line angle specs. are in the shop and assy. manuals. Did not have a problem when I went to the 4 speed. Leo

 

[dq409]

Posi chatter? Sometimes adding more special posi lube cures it.

DITTO !!!! I was going to post this but you beat me to it !!!

Just add a bit more posi lube and see it it gets better,, cheap fix,,,

 

[sam 15]

Here's a few links that may help re: pinion angle

http://www.streetrodderweb.com/tech/0707sr_driveshafts/index.html

http://www.rodandcustommagazine.com/techarticles/0608rc_driveshaft_tech/driveshaft_support.html

http://www.iedls.com/ptsetup.html

http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php

 

[LMBRJQ 60]

The Measurements

Hi All, Please bear with me on this as i explain where i was and where it is now.
All measurements were taken from the horizontal plane. Trans pointed down 5deg to the rear, first drive shaft pointed down 1 deg to rear (=4 Deg difference) second drive shaft pointed down 2.5 deg to the rear (1.5deg differential between front and rear drive shafts) diff pinion angle pointed 2.5deg down to the rear making it on the same angle as the second drive shaft. not good i guess?
I removed 3 of the 6 spacers on the banana bar and this has brought the diff pinion angle to 0deg from horizontal (2.5deg differential from rear second drive shaft) I spaced up the trans mount a bit to get the difference between it and the first drive shaft to just under 3 deg. is this OK with what you guys have found in the past
I havent driven it yet as having a mare lining up front sheet metal with hood and getting the rear of the hood to sit down (any ideas):?
I look forward to driving it tonight as it has to go over the pits tomorrow at 08:00 Thanks for your help
Steve

 

[LMBRJQ 60]

still there but not as bad

The shudder is still there but not as bad and has definately changed, as soon as i get access to a 4 post hoist (instead of axel stands on the floor or driveway) i will double check every thing. Cheers for all your help will keep posting the developments
Off to the authorities in 10Mins to see if i can get her legal.
Steve