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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 76chev454 on November 26, 2005, 01:04:00 pm

Title: Launch drive-train shudder!
Post by: 76chev454 on November 26, 2005, 01:04:00 pm: 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!
Title: Re: Launch drive-train shudder!
Post by: roundedline on November 28, 2005, 10:34:00 am: 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
Title: Re: Launch drive-train shudder!
Post by: Blazin on November 29, 2005, 06:21:00 am: Is the drive shaft out of balance, bent, or twisted?
Title: Year and model of truck
Post by: 76chev454 on November 29, 2005, 06:29:00 am: 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!
Title: Drive shaft and engine mounts
Post by: 76chev454 on December 03, 2005, 10:26:00 am: 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!
Title: Re: Drive shaft and engine mounts
Post by: roundedline on December 05, 2005, 10:01:00 am: 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
Title: Confusion?
Post by: 76chev454 on December 05, 2005, 11:00:00 am: 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!
Title: Re: Confusion?
Post by: roundedline on December 05, 2005, 02:39:00 pm: 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
Title: Re: Confusion?
Post by: DnStClr on December 05, 2005, 09:24:00 pm: 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...
Title: More shudder!
Post by: 76chev454 on December 06, 2005, 04:54:00 am: 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!
Title: Re: More shudder!
Post by: DnStClr on December 06, 2005, 03:07:00 pm: Here's a guy using the CalTracs syst- No hop..
Title: Big blower!
Post by: 76chev454 on December 06, 2005, 03:17:00 pm: 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!
Title: solved or what
Post by: 1tonson on March 12, 2006, 09:09:00 pm: have you determined the shudder problem would really like to know!
Title: Re: solved or what
Post by: ccb on March 12, 2006, 10:34:00 pm: 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
Title: not wheel hop
Post by: 1tonson on March 13, 2006, 02:21:00 pm: 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.
Title: More info on my installation
Post by: 76chev454 on March 13, 2006, 03:11:00 pm: I have a 76 C10 with original 454 CID bored 60 over. Axle is 12 bolt 3.42 or 3.43. Not real sure of that. Lots of goodies in the engine including roller lifters L5 heads and the like. Full hooker headers. Plenty of torque and power when needed. I am getting ready to put a new bed in and after I took the old bed off, I noticed the driveshaft angle to the rear axle is not straight. Asked a tranny guy about it and he said it should be straight. So, that is probably where the shudder is coming from at low speeds. Do not have it after about 35mph. -- Am enjoying the discussions. Thanks for all the input.
Title: Re: More info on my installation
Post by: ccb on March 13, 2006, 04:44:00 pm: If its not wheel hope, them the manual tran pressplate is warped or both.
Put there only guess with out seeing it.
Craig
Title: No wheel hop!
Post by: 76chev454 on March 13, 2006, 07:10:00 pm: No Craig, wheels are not hopping! I have added a system similar to CalTrec. Works very good. Driveshaft did not cause problems before trans was rebuilt. Any ideas about driveshaft alignment? How could it come out of alignment?
Professor of Interesting Stuff!
Title: Re: No wheel hop!
Post by: ccb on March 13, 2006, 08:42:00 pm: What has change from the last trans you had? What is diffrent? I think that where I would start. Is everything in the same place. Did you mark everthing be for you removed it?
So you could put it back in the same place. is everything lined up?

Craig
Title: Re: No wheel hop!
Post by: roundedline on March 14, 2006, 03:03:00 pm: 76chev454
What do you mean the driveshaft is not straight? As in it has a bend in it? Or it doesn't run parallel to the frame rails?
Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project
Title: Driveshaft~
Post by: 76chev454 on March 14, 2006, 03:31:00 pm: From the yoke to the axle, it is not parallel to the frame. I do have shims that I could install. By the way, at about 20 mph, no vibration is noted.
Title: Re: Driveshaft~
Post by: roundedline on March 14, 2006, 04:44:00 pm: You are talking about from the output yoke to the axle input yoke. This isn't supposed to be straight parallel to the frame. It will be angled some.

Drivetrains centerlines must be parrellel in all respects. Due to u-joints nature the operate best at an angle. As long as the crank centerline and the pinion centerline are parallel you are ok.
Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project
Title: Re: Driveshaft~
Post by: ccb on March 14, 2006, 08:22:00 pm: Its hard to give ya help with out see it. Chris said it best,
I think my question is still what has changes from the last trans? I assume you have a GM repair manual that tell ya how every is set up. I think there a formula for setting up the drive train I saw one in one of the truck web sites. If everything else check out I would say It may be worth a trip to rear end shop to see if some thing came loose.

Craig