Jump to content

GMC TopKick 7000 with a hop


Recommended Posts

10 hours ago, mikem said:

I'm a loooong way from an expert, but how do you "time" 3 U-joints in a drive shaft?

 

I believe that the front and back one are supposed to be in phase 

Link to post
Share on other sites
  • Replies 137
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Congratulations,  you found your problem. I'm a little put out. I said it was most likely a driveshaft problem before jmech but he gets the credit! You Yankees are discriminating against us

Did the hoping stop now that Easter is over?

The problem is in fact that you have been using Hy-Tran inside the driveshaft when you should have been using Official Yellow Wonder Bucket Fluid!!!

Posted Images

Jack up the rear end and set the frame on cribbing so the wheels are 6" off the ground.

Then with the box up, and someone watching the rear end and driveshaft, start it up and gently bring it up to speed.

Do this slowly as this can get out of hand and if as bad as you say, could try to jump off the cribbing. 

If it is that bad, then either the driveshaft will start to wobble, the rear end will start to jump, or both.

I am betting money on the driveshaft.

Most bigger towns have a driveshaft expert who can spin your shaft and find any issues.

 

  • Like 1
Link to post
Share on other sites
10 minutes ago, acem said:

But have you checked the phase of the flux capacitor?

I lent out my Flux Phasometer, haven’t gotten it back yet 

  • Haha 3
Link to post
Share on other sites

I'm with the boys who are thinking it's the driveshaft ,  most likely out of phase

Snap a piccy of the driveshaft

https://youtu.be/Idk3BVDVHq4

 

  • Like 2
Link to post
Share on other sites

Ok, driveshaft pics and findings, also video. I have 5 degrees at the tail-shaft of the trans and 5 degrees at the pinion, the joints are all in phase, i have tried turning it so they were not and the results did not change. Please excuse the video quality, it looked better on my phone but the youtube upload lost something.

also the vibration does persist even when coasting in neutral when jacked up.

 

A8EF1E4D-9244-44AA-B012-2EAFDFFE6D5B.jpeg

C25B486E-88A5-4A0A-BF82-351A515D171B.jpeg

111CE8C5-4BBE-4965-AA1F-621B9FAA5BA2.jpeg

453807E2-592D-4FC9-95F6-0D0B96598D2B.jpeg

320AD36F-B3B2-428E-9322-FEA8AE6EFA5B.jpeg

314EAD57-A84C-4EBB-8C18-8C4365302583.jpeg

FC92842D-947A-48F5-B2D6-876506DFDF43.jpeg

DE31096C-DD00-46E4-93F4-0B9314A57BE8.jpeg

Link to post
Share on other sites
1 minute ago, m.c.farmerboy said:

are those napa brand jack stands?

Hard to find a Jack stand made in USA, these were made locally.. i am into that . 

  • Like 1
Link to post
Share on other sites

If you shortened one of the line shafts did you have it balanced?

with the truck in the air and wheels turning slowly apply the brakes and see if there is a change

Link to post
Share on other sites
3 minutes ago, m.c.farmerboy said:

If you shortened one of the line shafts did you have it balanced?

with the truck in the air and wheels turning slowly apply the brakes and see if there is a change

all the u-joints must be in phase 

Link to post
Share on other sites
4 minutes ago, m.c.farmerboy said:

all the u-joints must be in phase 

can you drive it on the road and video the vibration ?

Link to post
Share on other sites

Make sure there is enough play in the jack shaft. If too tight it will bind .

  • Like 2
Link to post
Share on other sites

Did not balance shaft, made by local engine builder, joints are in phase in that the pinion yoke, slip portion of the lower shaft and trans output yoke are all in alignment.. as In pointed at each other. 

Link to post
Share on other sites
3 minutes ago, EASY BOB said:

Make sure there is enough play in the jack shaft. If too tight it will bind .

Jack shaft? 

Link to post
Share on other sites
9 minutes ago, acem said:

Have you verified the pto is shutting off?

It's a long shot but those ptos can vibrate.

Thx-Ace 

It is, also direct mount pump and cable control PTO i can feel it disengage. 

Link to post
Share on other sites
2 hours ago, vtfireman85 said:

I lent out my Flux Phasometer, haven’t gotten it back yet 

You have to be careful who you lend tools to.

  • Like 1
  • Haha 1
Link to post
Share on other sites

Tape a quarter to the driveshaft. If it gets worse move the quarter around to a different spot. See if it improves. Keep moving it around the shaft til you hit a sweet spot. Weld a washer on. Duct tape and 25 cents may fix it.

  • Like 1
Link to post
Share on other sites
11 minutes ago, 79vking said:

Driveshaft Phasing & Its Importance - Managed Mobile, Inc.Looking at your third pic after the video it looks like that shaft is incorrectly phased.

I have tried it both ways, however if i turn it 90 degrees that puts the trans output and pinion put of phase, i have been going on the assumption that keeping the phasing of those 2 correct was more critical 

Link to post
Share on other sites

I'm no expert but I don't think the trans yoke and the diff yoke matter. Just went out in the shop and looked at a truck ant the trans and diff are not in phase. The yoke in each shaft have to be in phase. Think of the original set up of this truck, when you engage the transfer case from road to pump it does not phase. Just the independent shafts on each side are phased.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...