Jump to content

320 third member change


212 320

Recommended Posts

  • Replies 22
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

what are the gear sets on the roadster Iam looking for 3.5 or3.7 thanks jeff

 

 

I put 350 gears in my 521KC SD25 diesel, I have the torque to get it rolling, no problems, I had 389s, I did notice the change.

Your NL320 is lighter, your LD20 likely has the torque to get it moving with the 350 gears, but 370s would be a lot easier to find, a lot of 720s had 370s.

Link to comment

Your a very lucky guy Jeff, guess what I found today, the second 720 I looked at today had 3.545 gears in it, and they were good, the gear oil was yellow, and the pinion was tight.

DSCN1455.jpg

 

DSCN1452.jpg

I looked for over a month for the set in my truck, I looked at the ID plate, and cleaned it off, because I thought I was seeing things.

We should talk, call me.

Link to comment
  • 9 months later...

So finally signed up on Ratsun, I know pics, pics,pics, I promise anyway doing 3rd member swap on my 320. My question is Sence gear tooth pattern is set with the pinion, witch is left alone with the side gear swap, backlash by shims in the side gears or ring and carrier? If I just swap the side gears, do I use the 320 bearings or the 720 bearings or are they the same. And finally if I put everythning (caps, shims ,ect) back exactly where they were, how much do i need to worry bout the critical setup, i.e.  backlash/geartooth pattern

Link to comment
So finally signed up on Ratsun, I know pics, pics,pics, I promise anyway doing 3rd member swap on my 320. My question is Sence gear tooth pattern is set with the pinion, witch is left alone with the side gear swap, backlash by shims in the side gears or ring and carrier? If I just swap the side gears, do I use the 320 bearings or the 720 bearings or are they the same. And finally if I put everythning (caps, shims ,ect) back exactly where they were, how much do i need to worry bout the critical setup, i.e.  backlash/geartooth pattern

 

When I do a side gear swap for a 320, I find a tight 3rd member out of a 720, then I use the 320 side gears(spiders), the shims that come with them, and the block in the center, everything else I re-use in the 720 gearset, 720 gearset, 720 bearings, that way nothing has to be set up, as I have changed nothing having to do with the ring and pinion.

Link to comment

Thanks Wayno, This is Aaron in Battleground with the little white 320( ive talked with you several times ,once or twice about this in general) anyway thanks for setting my mind at ease. I was 95% sure that by just changing side gears I would be free of the sett-up headache but as you know a R&P can be a pretty precise mech. Any little secrets or details that might hang me up that you know of feel free to post up if you have the time( i.e. anything that wouldnt be self explanatory by just tearing into it and paying attention) I have above average mechanical skills but not a expert by far and diff.s are something my knowledge of is all book and theory and at this time not hands on. So wish me luck, oh, do the side gears and bearings have to be pressed on/off or is it far easier than im thinkin? Thanks again, and take care

Link to comment

I am assuming your the white 320 that stopped when my 521 was over heating.

It can sometimes be a bitch to get the pin out of your 320 3rd member, the 720 uses a expanding type roll pin, when the 320 uses a solid roll pin, at the factory they put the pin in and then deform the side of the hole with a punch, you have to use a drill bit to make the hole round again, then you use a long narrow punch or nail and force the pin out of the hole, then you can remove the spider gear shaft that holds the center block in position, which allows you to twist the spider gear side gears out, ect. ect.

You can actually set up a time with me and we can do it at my house, I already have a set of side gears out, so as long as yours are good, we can trade your side gears for mine, basically you bring what you have over here and we set up your gearset with my side gears, then you install it in your truck and you leave your 320 gearset with me as long as it is good.

There is a lot involved with doing the transfer, it's not that hard to do, but it takes a long time to explain the whole procedure, getting that pin out is the hardest part.

Link to comment

First, yeah your picturing the right guy, second thanks all ready for your help so far, if I get frustrated ill give a shout for some help but ive got alot of time on my hands so im going to give it the ol college try myself first. Prior to tearing any thing apart ive noticed that my 320 donor 3rd has some excessive play in the side gear to carrier clearance. The 720 side gear clearance should be around .005 to .008 or so , it is, and feels tight by hand. dont know the spec on the 320 but its real sloppy by hand and can get .025 feeler gauge in it. I think im going to pull another 3rd seeing as how ive got 4 320's around,and it only takes me about45 min to do so. Ill compare the two or three and see if the first one i pulled isint maybe just a little worn. My 720 3rd feels tight in the sides and spiders and thanks to your posting i checked for slop in the pinion as well and it feels nice(thanks for the tip). Going to see how the 3:89's do with the 4speed and strong pulling j15. Will keep ya posted! Thanks again Wayne...see ya soon im sure

Link to comment

Second donor third feels much tighter as far as side gear clearance goes. Hope im not over simplifying this process, but it does seem somewhat self explanatory once you look at it. Wish I could find a 78/79 donor 620 chassis so I could enjoy discs and balls joints as easy as I hope this 3rd swap seems. Anyone?(standard cab short bed)

Link to comment

I am not sure what you are talking about when you talk about "side gear clearance", are you talking about axle play when pushing the axle in and out, or are you actually talking about the pinion flange gear play, which is actually ring gear/pinion gear play(tighter)?

When I buy a 3rd member for my rearends, I look for pinion flange play of less than an eighth inch, and I prefer only a sixteenth or less, which is hardly any movement if you were to grab the driveline and twist it when the transmission is in neutral.

 

I hope I am making sense to you.

Link to comment

Im just talking about the amount of space between the side gear(spider) and the carrier. 2 of the thirds are nice and tight but I have 1 that is really sloppy. Not sure if there is a brass spacer type bearing in there or if its just a wore out gear. Since these are the parts im transplanting into my donor(720) 3rd, I just trying to use the best ones I have. Hope that clears up my babbeling!

Link to comment
Im just talking about the amount of space between the side gear(spider) and the carrier. 2 of the thirds are nice and tight but I have 1 that is really sloppy. Not sure if there is a brass spacer type bearing in there or if its just a wore out gear. Since these are the parts im transplanting into my donor(720) 3rd, I just trying to use the best ones I have. Hope that clears up my babbeling!

 

I have never seen sloppy side gears before ever, but I have seen a lot of ring and pinion gear slop before, if the spider gears are loose in the carrier, the whole thing is toast.

Link to comment

I can't remember if the truck diffs have shims/thrust washer behind the side gears, but the R160/R180 diffs do. They can wear out, and the gears can wear into them both scenarios causing execessive play. I don't know what the spec is, but if it's more than .010" I'd say there is a problem.

Link to comment
I can't remember if the truck diffs have shims/thrust washer behind the side gears, but the R160/R180 diffs do. They can wear out, and the gears can wear into them both scenarios causing execessive play. I don't know what the spec is, but if it's more than .010" I'd say there is a problem.

 

The old stuff has copper shims, the newer stuff is some silver metal shim.

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.