Started checking out my rear end and found that I have a 3.42 open. Tube stamp 'TL' - (3.42 open w/fr. drum brakes). I'd like to upgrade this to an anti-spin. (code TM/S9)



I counted and it looks like I have 31 spline axles. My current open carrier is '359', but I couldn't find any refs to this number.

Seems like the aftermarket 'posi' carriers won't work because they're all 28 spline and my housing is for a 4 series carrier, not 3 like most of the aftermarket 'posi' conversions. It looks like I'll need an Olds 672 carrier. A 672 should 'drop in' and I can keep my gears.

Is this correct ? Is there a better way while retaining my original housing ?

I just wanted to confirm all of this before hunting for a 672.

Trivia - Any one know what the "317" written on the ring & pinion mean ? It doesn't match my body or VIN. An inspector/assembler stamp ? Just curious...
Thanks

 

317 is also on the pinion you will see it when you clean the pinion off with kerosene that just keeps the gears as a set before they get in the housing. Probably an inspection mark. When lapped or installed in the housing. What are the numbers stamoed in the edge of the ring gear?

672 will still be a tough one to find. I have a housing with no spiders or clutches... pinion pin hole is starting to oblong so probably this carrier was raced I am sure.

 

Ya, its on the pinion too....you can kinda see it in the 2nd pic if you enlarge it... I figured it was just some ***'y markings (although I was secretly hoping it meant that it was some rare high dollar thing that could finance my posi desires! ... )

Looks like "3 - 2A41 GM UL 6A(or G4 or ..?) "
Makes sense...41 tooth ring / 12 tooth pinion = 3.42

Gah...that's what I was afraid of....

Looks like my options are :

1. Find a 672 & install
2. Live w/ the pegleg
2. Convert to 28 spline which opens up my aftermarket options
3. Give up & swap out the whole rearend for a non-O/corp...or *gasp* a C-type.

Any idea what the going rate for a 672 is ?

Thanks for your input, monzaz.

 

Try Supercars Unlimited (www.supercarsunlimited.com). It seems to me that they have posi unit conversions for everything up to 3.23 and then again most everything from 3.42 up. You should be able to look at their catalog from the site provided.

 

Have you checked with Brian Trick (507olds)?

 

I have the 672 carriers.

 

Yes ! and he emailed me and said...

Thanks everyone!

 

Follow up....
The fresh 672 posi...er, 'Anti-Spin', unit that Brian Trick provided is now surrounded by my original 3.42 gears & comfortably living in my refurbed housing.




Another round of thanks to all that helped..!

Piece by piece....

 

Great to hear,& that looks purdy! That #359 carrier has to one of a very few,for the 12-bolt o-axle,non-posi,31-spline & 3:42-up ratio.

 

Thanks Brian!

Now the bad news...

I had just thrown the W-27 cover on to see how it looked. I pulled it back off to paint the bolts and found this....

click for big..

What's wrong w/ this picture ?!?!?!?! Grrrrrrrr...

 

You have the passenger side cap on backwards?

 

Not me. The guy I paid to do the rebuild....
I also don't see any marking paint for mesh checking...

He came recommended...& that he knew Olds (& other older stuff like 50's Cadillacs, Ponchos, etc..). He seemed to ask the right questions / say the right things when I was at his shop.

I just called him and after a bunch of hemming & hawing, talking about the arrows don't neccessarily mean anything, etc..., he finally said "Well, I must've put it on wrong."

He assured me everything else is OK and that I can just flip the cap and torque to spec.

Problems now are:
- His shop is a 3 hr roundtrip away
- I just cleaned & re-painted it....
- Do I trust him ?

So, can I just carefully flip & torque ? & then check the mesh w/ paint ? Or do I need another round of rebuild ?!

I'm spittin' nails right now....

 

Well I just did a rebuild myself, it was my very first. but some things to think about, are you sure that the caps for whatever reason were not that way from the factory? unlikely but maybe it was possible.? I don't know, mine pointed out the correct way, I would at least do the following

get some mesh checking grease, and check the pattern.

go to harbor freight or wherever and invest in a magnetic base and dial indicator, and check your backlash, that is probably the most important thing.

I had INVALUABLE help with my diff rebuild from Jim At JD Race (Monzas), Man it was like I had him on speed dial, and he was great about it, I am sure Brian is the same

I think you could probably switch the cap, and be fine, but why not check the backlash and pattern yourself, that part was pretty straight forward, but now is the time to check it!!!


and your housing looks great....

 

I know ! And your thread about it is great !

I only wished I'd read it before I went this route. I prolly would've bought the tools & done it myself. I was hesitant due to inexperience with rearends. I always thought there was some 'secret knowledge' required to do them properly but with your thread & my CSM I'm now sure I could've done it.

The right cap is def upside down. See 2nd pic in my first post.

Looks like I'm headed to get dial gauge & some marking paint. I'm curious & suspicious at this point because even before I noticed the upsidedown cap there seemed to be much more play in the gears than it had originally. There's a distinct clack when turning the pinion back-n-forth and I can visibly move the ring gear back-n-forth. I remember the original having almost no play at all...

 

You can flip the cap & retorque,but I would also wonder if each cap is on the side that they originally came from.Is the driver's side still on the driver;s side,etc.? The arrows ALWAYS point outwards.Those caps have a slight curve to them.They are not straight,& they are machined to the bearing bores. If you're in a pinch,grab some lipstick & smear some on & run the pattern.Lash compound would obviously be better,if you have it.If you can get some type of compound on there & send a picture,I can guide you from there.

Don't feel bad.There is one main differential shop here in my town,& I have seen a fair share of their mistakes as well,including having the caps backwards.I just saw one of the "experts" the other day.He was working at AutoZone.

 

I'm pretty sure the caps are still in their proper L-R position. When I was talking to the guy he asked if there was paint on the right cap since he always marks the right...and there is. When we got around to talking about the curvature of the cap, he finally said he must've done it wrong.

I'll post pics once I do some measuring/marking....

 

with Brians and /Or Jims help, I am sure you'll get it sorted looking at the pics the left side seems to be in the same orientation, but one thing I ran into and I "Thought" I was being very very careful was I "switched" the two production shims, and even though they looked exactly the same ( by eye, one was .243 the other was .237 using my cheap digital micrometer! LOL.. which made the backlash too far out ( around .012 I think) by reversing them it brought it to .008.

I am wondering if he used a NEW crush sleeve when he set the pinion bearings? this needs to be done before all the rest, if that isn't right nothing will be right.


Please bear in mind I am only passing on the great advice I got, and have read and researched, I do not have any experience doing these things, I am just being a parrot, but without the cracker reward, and passing on some of the little pitfalls that "could" happen

 

Yes,often the carrier shims look identical to the eye,& might even be real close in width,but they are almost always different.The one I just did last night was .250 on the left,& .247 on the right.This was an original 70 O-axle 3:91. I have had others like .258,& ,235.Much different.I wish I was closer,I'd help you out. I do make it into Ohio a lot,to deliver rears,but you are still a drive from that.

 

by any chance, did you have a guy in Spencer Indiana rebuild this rear end? i just had one done by him and one of the axle seals is leaking. i called him and he said that the housing must be wore around the outside of the seal and he would fix it with RTV? how could the housing get wore when the seal don't move?

 

Yessir.

 

I hope this turns out better then it is sounding?
seals leaking, parts on backwards... lawdy!!

 

i hope it is just some temporary bad luck on his part. i was told by many people that he was the best around. i have some friends that all have theirs done there and had no problem. i am taking my car down next week. he said he would get it apart to see what happened. he said he could have it fixed without me having to leave the car.

 

If you have a 70-newer rear,with SET-9 roller bearings,& you install the bearings backwards,they "can" cause the seals to leak.Sounds odd,but that's another one of those mishaps I've had to correct for the experts.I'm not saying that is your problem,but it could be.Your Timken SET-9 bearings have clear instructions stating which way to install the bearings,but they still seem to find their way on the wrong way.maybe it is a Jap bearing/seal.Maybe you don't even have this type of rear,or bearing.

 

Exactly where I'm at. I had 3 different people rave about / recommend him. Each person had 2-4 diffs done by him w/ no probs. I've talked to 2 of them now and both times got shrugs & "Well, he is gettin' older..."

Yeah ? Well, so am I !

Picking up tools today to check it. I really do not want to haul it somewhere now that its in final paint....

 

just curious to how your making out... did you check the backlash?

 

Not yet...Got the tools & then got swamped w/work......I'll prolly do it tonight/tomorrow...

 

good luck then, just hoped it was all ok and you can reinstall. keep us posted!

 

well, i will be there tomorrow after work. he said he would have it fixed and i can take it home without having to leave it. i hope so. i am betting it has the wrong seals in it. the other side is starting to leak now. this is an O type SH code from my 70 Rallye 350. 507OLDS, do you know what the right seals and bearings would be? when i took it to him it had a growl to it and that is fixed but it did not leak before i took it to him.

 

when i added the fluid i just put it the amount the book said and put the cover on. i did not check the level with the plug after it was in the car. if i did not measure right and overfilled it would that cause it to leak?

 

I don't know, I have always filled the diff from the side plug, when it starts to come out then it is full? I have done this forever! but since the fluid is not under pressure why would it push passed the seal? and if for same crazy reason it would push past wouldn't it push past the pinion seal too?

 

good point.

 

OK....here's the scoop....

Pulled & flipped the right cap. Torqued to 65ft/lbs (& checked left..was at 65)

Checked backlash per the CSM...



Uh oh...Looks like ~.010-.012 all the way around (checked 6 diff places)....

Pattern (using Oil of Olay ColorMoist Lipstick Moonlit Mauve #305 - a personal fave...)


click for big...

So .010-.012 is too much, right ? CSM just says min .005-.009....
???

 

The drive pattern looks great.Try swapping the shims to the opposite sides to see if you can bring the backlash down a hair.If the the shim that is currently on the passenger side now,is thicker,you are in luck.This was an easier swap since the gears were originally from this housing.The pinion depth was already there.You just need to nail down the backlash.Mic both carrier shims to see what you have.I like the color.

Jensenracing77,
The bearings for the 70 O-axle shafts are SET-9 or also known as A-9,depending on the brand of bearing.The seals are 712146. The earlier style bearings will not fit,so I am guessing that the correct ones are on there.

 

Yep. That's what I thought. If I understand it right, I'll need to move ~.005-.006 worth of shims over to the driver side to bring the backlash down .0025-.003. That ought to put the average backlash at around .008-.009. I'll do that & report the outcome....

 

I Like a little deeper red lipstick, but some foks think it makes the gears look trashy, I think it's Hot!! J/K


It LOOKS like you have the Factory shims in there, you need to mic each one to see the difference, this is exactly what had happened to mine the factory shims got reversed, you need to be SUPER careful with those factory shims!! they are smaller and very brittle!

I think if Both Factory shims are there, just reverse the whole enchilada? but you will need a micrometer to measure the thickness...

also the carrier will take a little prying to get it up and out, you'll need to remove the axles etc first, I used two long brass drifts on either side and pried mine out that way.

Brian does this sound right? again this is what I did...

 

Darker red...? Hmmmm, I was kinda going for the bubblegum kidstuff look ! A note on lipstick - Its fragile. I first tried to dab it on from the holder. On the 2nd tooth the whole damn thing broke off and fell down in the housing....under the edge of the pinion gear. I spent 5 mins fishing that slippery little sucker out of there & ended up covered with a nice mix of lipstick & gear lube....on my hands & face where I'd brushed my cheek. My wife came out to ask me something, laughed a little, shook her head, and went back inside without saying anything...
From then on I used a Q-Tip as a paintbrush...

Haven't had a chance to inspect the shims to see if they're the originals or if there are any extra add'l shims. I prolly won't get to it until Sunday. I'm hoping that the original factory iron shims are just swapped & the math is right. Switching these would be easiest. What I don't want to see is the thicker shim on the driver side.

Axles are not in it. I haven't re-installed them yet so I should be able to just pull the caps and gently lift/pop out the carrier. I think the carrier bearing preload is good. There's no descernable side-to-side play at all, but it still turns OK. I have 2 big prybars to help.

When I pulled the axles I just used my hillbilly improv slidehammer method. I bolted a 4+ ft piece of engine chain to 2 opposing lugs. Wrap bigazz hammer with chain. Get slack in chain and yank. Repeat as neccessary. Both axles popped loose on 2nd medium force yank. After the first 1/2" or so I just pulled them out by hand.

 

Ok, well good luck on sunday, I know this is tricky, and I was quite daunted by all the measuring etc, but I have to say ones it is done and I know everything came out ok, I felt ( still feel) Great!!

I will be painting the brackets etc for my disc conversion and then hopefully putting mine back in, yours shouldn't be long in going back either!!

 

BTW, I do have shims left over, and your welcome to them if you need them.

 

i just got back. right away he found that the axles had end play. he said that should never be with bolt in axles. he thought that the bearings may not have seated all the way. we took the axles out and found that the bearings were all the way on so he was not sure at that point what it was. after taking several measurements he could not figure out what part was the problem. he looked at his book and then showed me. the book showed 2 differant seals. a thick and a thin. it looks like he had got the thin seals and needed the thick seals. when the thin seals were all the way in there was nothing left for the plate to pinch. he did not have the thicker seals so i have to go back Wednesday. i would not have figured that there was two differant seals but his book shows them. he is concerned that the thicker seals won't fix it. he said if it don't he will have to shim it to get the end play out. does any of this make sense to you guys?

 

Shim what? the bearings are pressed on, once they are in the housing they are in, now I know Jim at JD race asked me what kind of bearings I have and mine are the permanently sealed kind, when I tapped the axles seals inwith a seal driver, then push the axles with bearings in there is a slight ridge ( which is normally taken up with the backing plate) then the end cap, is he thinking to put shims between the end cap and the bearing?or vice a versa? I think once the new seals are in the seal housing will occupy much of the space that the bearing is sliding into giving you that play.

(btw) same caveat as always I have only done 1 diff, so I am basically thinking out loud