shaking! what is it?

[theredmeadow]

also, is it hard to replace that whole differential assembly? like the whole casing piece? I'm looking to keep my same 6 lug axle shafts. I can't find any videos on it.

[jjzepplin]

WELL... 3.73's would be nice for the quarter mile but on the highway with a 3spd auto you'll be winding up pretty good at 65+ miles an hour and spending some coin for gas too. Decent towing gears though.
Rear diff is easy to R&R. Easier than rebuilding your old diff. Just make sure the new one is good and tight or your in the same boat.
Swapping axles is easy. Small bolt that holds a big center pin in comes out and then push your axles in a bit to release a "c" clip and then pull the axle. Only torquing the small bolt is the only measuring you'll do. Axles have to be the same length though as some earlier diffs are not as wide.

[geezer#99]

Don't waste more money buying a 5 bolt rearend. It's wider than yours. About 2 inches.
The axles don't swap either. Different lengths.
Take your truck to a mechanic and get their opinion.

[theredmeadow]

ok so the 5 bolt diff is going to be a different length than my 6 bolt? before I buy I'm gonna have the guy get me a couple measurements. also i'm paying $125 for it, is that a decent price?

[CC69Rat]

Is the truck lowered at all? Maybe I missed it (I read most of this one on Friday at work, just forgot to post)

What if the pinion angle is off, caused the problem he is having now .. just thinking maybe it wont be too long before the new one is coming apart ?

Can you post a picture of the snout of the pinion in relation to the drive shaft when the truck is at ride height ?

I agree I think it's the pinion / carrier bearing (or both) .. but what caused it?


Your truck being a 70 model it could have two different axle lengths in it. The easiest way I have learned to tell is to lay down underneath the truck (.. under the back bumper) .. have a buddy or maybe the wife hold one end of the tape measure to the back side of one brake backing plate. Then measure across to the other side in the same spot on the backing plate. IF the axle housing is 57" you have a later housing. If it is 55.5" you have the earlier housing more common in the 67-69 trucks. 70 was the transition year. In 71 with the addition of front discs the rear end housing was lengthened 1.5". So if you have a late, 6 lug axle your original axles will bolt right up to a 71-72 housing (should you decide to replace the whole thing) If it's an early 6 lugger I'd keep the housing you have and rebuild it. (Just me ..) An early 6 lug housing will have 30.5" long axles in it .. measured from the wheel mounting flange to the end of the axle splines. The later one is 31 5/16 long at this same point. Say you have 57" long housing, at least you know how long the axles are before you take them apart. Keep in mind though if you swap housings and it's a 71-72 that hasnt been gone through then you're still using 40+ yr old bearings etc. What I'm saying is it might not be a bad idea to rebuild it which ever route you chose. I have seen 70 model trucks with both housings / either. I think they just depleted the stock of the earlier trucks then the later build 70's got the longer axle housings.

Another thing to consider is say you were to swap to another housing and it's the later one .. your backspacing on your wheels will be impacted .75" on either side if you have the early housing now. Make sense? Hope this helps.

I'd have a look at your pinion angle though especially if the truck has been dropped.

Good luck man ..

[theredmeadow]

Yes the truck was dropped 4-5 inches when I first got it but I've raised it back to the stock height. You think that was what may have caused it? I just measured it and from the back plate to center it's about 29"? I'd say from end to end including back plate it's close to 61". I'd say from center to end it's close to 31".

Originally Posted by CC69Rat

Is the truck lowered at all? Maybe I missed it (I read most of this one on Friday at work, just forgot to post)

What if the pinion angle is off, caused the problem he is having now .. just thinking maybe it wont be too long before the new one is coming apart ?

Can you post a picture of the snout of the pinion in relation to the drive shaft when the truck is at ride height ?

I agree I think it's the pinion / carrier bearing (or both) .. but what caused it?


Your truck being a 70 model it could have two different axle lengths in it. The easiest way I have learned to tell is to lay down underneath the truck (.. under the back bumper) .. have a buddy or maybe the wife hold one end of the tape measure to the back side of one brake backing plate. Then measure across to the other side in the same spot on the backing plate. IF the axle housing is 57" you have a later housing. If it is 55.5" you have the earlier housing more common in the 67-69 trucks. 70 was the transition year. In 71 with the addition of front discs the rear end housing was lengthened 1.5". So if you have a late, 6 lug axle your original axles will bolt right up to a 71-72 housing (should you decide to replace the whole thing) If it's an early 6 lugger I'd keep the housing you have and rebuild it. (Just me ..) An early 6 lug housing will have 30.5" long axles in it .. measured from the wheel mounting flange to the end of the axle splines. The later one is 31 5/16 long at this same point. Say you have 57" long housing, at least you know how long the axles are before you take them apart. Keep in mind though if you swap housings and it's a 71-72 that hasnt been gone through then you're still using 40+ yr old bearings etc. What I'm saying is it might not be a bad idea to rebuild it which ever route you chose. I have seen 70 model trucks with both housings / either. I think they just depleted the stock of the earlier trucks then the later build 70's got the longer axle housings.

Another thing to consider is say you were to swap to another housing and it's the later one .. your backspacing on your wheels will be impacted .75" on either side if you have the early housing now. Make sense? Hope this helps.

I'd have a look at your pinion angle though especially if the truck has been dropped.

Good luck man ..

[theredmeadow]

these are the measurements I was given by the seller. He also said that he put 5 lug axles in it and it originally had 6 lugs.

63 1/2 from wheel mounting surface to wheel surface and from the middle it's 29 1/4 to where the axle comes out

[CC69Rat]

From the backside of the brake backing plate on the drivers side.. to the same spot on the passenger side should be 57". It sounds like a longer housing in it now.

It kinda sounds like the pinion was set for the 5" drop.. then raised to stock and not readjusted (?). Post up a pic if you can.. I'm just curious to see it.

[theredmeadow]

Originally Posted by CC69Rat

From the backside of the brake backing plate on the drivers side.. to the same spot on the passenger side should be 57". It sounds like a longer housing in it now.

It kinda sounds like the pinion was set for the 5" drop.. then raised to stock and not readjusted (?). Post up a pic if you can.. I'm just curious to see it.

[CC69Rat]

Its not bad but it does look a little off to me.. the pinion snout will rotate up toward the bed floor under acceleration..

Maybe some others will voice their opinion on it.

I could be totally off here,.. I just like to know why it failed so I can better understand how to fix it when stuff like this happens to me.

[theredmeadow]

yeah I ended up not buying the differential. i'm going to take all your advice and have it serviced/rebuilt? that way i keep it all the same and not have to worry about it being modified. i didn't like the sound of going with the 373 ratio either. i'd rather have it smoother at higher speeds.

[imjeff]

That pinion should be down below the plane of the driveshaft. Ideally equal and opposite the angle going into the transmission.

[theredmeadow]

will re-adjusting it help the vibration a bit?

can you show me a pic of what you're talking about?

[CC69Rat]

Do you guys think it might be a 'jump rope' issue with the drive shaft ?

It wouldn't hurt to put some (maybe 3 degree) pinion shims in it and see if that clears it up. I agree the snout of the pinion looks a little high to me.. it needs to be rolled back down a little.

I'll post some pics in the morning unless someone beats me to it

[theredmeadow]

after looking into what you guys just said about the angle, I agree that it seems that my pinion is point up too high. How can I adjust it so the pinion angle is lower towards the ground? Is it something I can just turn the whole differential downward??

[theredmeadow]

are there any instructions on how to adjust the pinion on coil springs? All I see are videos about using leaf spring shims. I don't get how you adjust it with coil springs.

[CC69Rat]

Here is a very good write up on it. I'm an old Camaro guy from way back, I have restored several and use this site about as much as I do the one below.

http://www.nastyz28.com/forum/showthread.php?t=221794

Not being able to actually see the truck and / or ride in it I cant tell ya for sure but I do think somewhere along the way the pinion angle in your truck has been adjusted. I'll post a picture here in a sec that explains it a little better. The post above is huge but it will help it make sense. From the trans tail shaft you want equal and opposite (as mentioned) angles. You want the two to cancel each other out. Otherwise you will get a jump rope effect. The drive shaft is longer when it comes across the top of the rotation but shorter as it goes underneath creating a harmonic vibration at a certain speed. Usually it's at 64mph.

When your truck was dropped orignally my thinking is someone knocked the perches off the axle tube and re-welded them on (?) to correct the pinion at 5" drop. When you raised it back up the correct angle at the 5" drop is no longer correct at stock height. - OR - could it be it has pinion angle shims in it now? Could we just take the shims out of it and correct the angle back to stock? Post a picture looking at the rear axle housing from the backside. (Under the rear bumper looking back toward the axle housing where the shock connects.

[theredmeadow]

So I should get those pinion wedges? Is there one in specific I should be buying? Do you have a link? Thanks.

Here's where I think you're talking about.

Originally Posted by CC69Rat

Here is a very good write up on it. I'm an old Camaro guy from way back, I have restored several and use this site about as much as I do the one below.

http://www.nastyz28.com/forum/showthread.php?t=221794

Not being able to actually see the truck and / or ride in it I cant tell ya for sure but I do think somewhere along the way the pinion angle in your truck has been adjusted. I'll post a picture here in a sec that explains it a little better. The post above is huge but it will help it make sense. From the trans tail shaft you want equal and opposite (as mentioned) angles. You want the two to cancel each other out. Otherwise you will get a jump rope effect. The drive shaft is longer when it comes across the top of the rotation but shorter as it goes underneath creating a harmonic vibration at a certain speed. Usually it's at 64mph.

When your truck was dropped orignally my thinking is someone knocked the perches off the axle tube and re-welded them on (?) to correct the pinion at 5" drop. When you raised it back up the correct angle at the 5" drop is no longer correct at stock height. - OR - could it be it has pinion angle shims in it now? Could we just take the shims out of it and correct the angle back to stock? Post a picture looking at the rear axle housing from the backside. (Under the rear bumper looking back toward the axle housing where the shock connects.

[CC69Rat]

Maybe if someone out there could take a picture of a stock height trailing arm setup and see if the saddles look like they are in the stock position? To me it looks like they have been cut off and rewelded.. maybe when it was lowered. My truck is not at stock height and 45 min away.

It does kinda look like they have been rewelded to me but I'm not sure.

The best place I know to get the shims would be Boris (he's a board member). If you send a Private Message to 'way2lo2'.. I'd suggest 3 degree shims. He has the best ones I know of.

.. or you could redo the saddles.. . Shims are just easier.

[theredmeadow]

Here's an up close picture, may it'll help?

Originally Posted by CC69Rat

Maybe if someone out there could take a picture of a stock height trailing arm setup and see if the saddles look like they are in the stock position? To me it looks like they have been cut off and rewelded.. maybe when it was lowered. My truck is not at stock height and 45 min away.

It does kinda look like they have been rewelded to me but I'm not sure.

The best place I know to get the shims would be Boris (he's a board member). If you send a Private Message to 'way2lo2'.. I'd suggest 3 degree shims. He has the best ones I know of.

.. or you could redo the saddles.. . Shims are just easier.

[CC69Rat]

Tough to say really .. again I could he wrong but I think somehow the pinion snout has been rotated up a little... hard to say on the saddles (the U shape that's underneath the axle tube but on top of the trailing arm). A lot of guys will cut those welds loose and rotate the saddle around a little and weld them back k on.

Something looks a bit off to me I just can't quite figure out how it happened or where .. (?)

Maybe a pic of a stock height factory setup to compare it would help.. humm..

[theredmeadow]

So the reason it all looked off was because of these mods! I didn't realize it till I started really looking into it. Keep in mind I've never had an all original C10 so I had no idea what I was looking at.





What is the piece that's cut? Is it hard to find it? Also, what about the whole drive line/shafts? Isn't it supposed to be a 2 piece?

[jjzepplin]

HOLY CRAP dude! don't drive that truck!!!!
I have one of those for sale.
$40 plus shipping.

[theredmeadow]

what could happen? What's the name of the part?

I may just have to buy it from you.

[CC69Rat]

Dude I have never ever seen that. Wow! I'm not sure its possible for it not to shake with the cross member cut. Scary stuff. Definitely needs replaced and will be a lot of work especially with the cab and bed on it.