Jump to content

620 hub differences?


J's 620

Recommended Posts

  • Replies 47
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

When your brake pedal is up, at rest, there should be a tiny bit of play on the pushrod........you should be able to wiggle it a bit.  If it's tight, either your pedal spring is not pulling the pedal arm up well enough(is it all the way up against the stop?) or the pedal stop is not adjusted correctly.  Do you have an adjustable pushrod?   On the 521's, they were not adjustable.  If this is the case, then make sure that the pedal bump stop is not holding the pushrod in tight.  You want about an 1/8" of pedal movement before the pushrod becomes snug.  The symptoms of your problem sound like the push rod is not being released all the way back.

 

If you pushrod is set correctly, then this is my next guess. 

In calipers, the square cut oring is supposed to be the "spring" that pulls the pistons back just a tiny bit........so, my guess at this point is the residual valve in your m/c is holding the fluid more than the calipers are expecting. 

 

Second vid on this page may help if you haven't torn apart an m/c before.  I'm not absolutely positive the stock single reservoir m/c has the same valve in it, but most likely.  The quality seems pretty poor.....guess I should try to find the master and load it to youtube at some point.  I'm not exactly sure how your brakes will act if you remove the rubber pieces with the slit in it.

Link to comment

Yeah load it and I will watch it! And guys, I really do appreciate all the input and advice. I am grateful that you took the time to reply to my post.

I think I may have been having this problem before I swapped the drums for discs. The truck did feel like it had a drag....I just assumed it was the bearings (after seeing the bearings). The grease in there was all rusty and mixed with water.

This poor truck sat for many years in an old man's yard along with other datsun vehicles. A guy bought it, did some shotty "restoration" and sold it to me shortly after. I actually want to keep it and do it right. It's a bit rusty and runs great.

Link to comment

In calipers, the square cut oring is supposed to be the "spring" that pulls the pistons back just a tiny bit........so, my guess at this point is the residual valve in your m/c is holding the fluid more than the calipers are expecting.

 

That would be my guess too. Drum type master cylinders have a 10psi residual valve. Disk type 2 psi....

 

Using dot 5 silicone fluid can also cause brake drag. The silicone lubricates the square o ring mike mentioned too much and does not allow the o ring to stick to piston enough for them to slightly retract. I found this out the hard way.....

 

The wobble might be a bur on inside of hub where races bottom out. If you used a hammer and punch to remove races, theirs a good chance you might of nicked it and race is not sitting flat in the hub?

  • Like 1
Link to comment

The brake pushrod wasn't adjusted right. I seem to have got it now. The brakes stop the truck and seem to release properly. Although I still have that warped hub problem.

There are no nicks inside the hub to make the race crooked. I did a good job of making sure I took my time and was very carful with the hammer and a drift punch. It's the hub itself that is damaged. Possibly the spindle as well. I will never know for sure untill I find hubs that are in good shape to compare with mine.

Link to comment

Can you take a vid of it spinning.  I've come across bent hubs before, but it's always been on the wheel mounting surface.  A bent spindle won't cause a wobble.....the wobble has to be coming from a rotating part.

Link to comment

Hmmm.....good question.  It would obviously need to be from a truck.  I would think so, but I haven't checked it personally.  You have 620 drum spindles......so you want to make sure you use 620 drum inner bearings.  The 620 hubs have metric studs.....the others will have Imperial. 

Link to comment
  • 2 weeks later...
  • 2 weeks later...

Now since I am basically doing this brake swap all over again using the Klotz kit.....I will have numerous photos for all to see. I have even shot a vid of my old hubs turning so we can all see how they wobble. I will show the wilwood kit on the truck as well, right before it comes off. It does look cool. It will be up for sale.

Thanks for shipping the kit Mike. Hopefully I have a project this weekend. Ya!

  • Like 1
Link to comment
  • 1 year later...

My dead thread will go into my build thread someday. The wilwood kit will NOT be going back on for viewing purposes. Too much work and my 76 hubs were junk so I tossed em. My brake swap went smoothly and the truck stops very well. Thanks to all for the input. Sorry for the absence of pics.

  • Like 1
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

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.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.