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Discussion Starter · #1 ·
What is the giulietta pinion preload in inch-pounds by itself,and also the combined or total preload with ring gear included? I understand that the ring gear preload is .008"-.012",but that it can also be measured with the string/spring scale method using inch lbs.? First time for me,any help appreciated.Regards,Phil D 61' 101 spider N.
 

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Richard Jemison
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Preload

Just to be clear.
The Preload is set by the internal shim pack and steel tube separating the fron and rear bearings. when correct the amount of torque on the nut is irrevelent, other than to have adequate locking load.

If you have changed bearings and anything in the original shim pack I wish you luck with noise!

The nut should be installed with locktight to about 70 lbft only when preload is finally set correctly. All you need while setting preload is enough torque on the nut to completely compress the shim pack fully. 20 lbft should be more than enough.

Preload about 3 inlb. I would never load bearings with closure of .008 past "0" fit. That commonly will lock up the bearimgs/race and they will burn up quickly.
 

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Discussion Starter · #3 · (Edited)
RJ,OK,so (1),appx. 3in,lbs. for the pinion preload,with the nut at 20ft.lbs. to check this is plenty. That .008"-.012" was something that I read for the ring gear/side bearings.(2)Are you saying that 3 inch lbs. is good for the ring gear preload too?The inner/rear pinion bearing is good,so I'm leaving it alone along with its shim pack ,to retain pinion depth. I'll be using a new front/outer pinion bearing as well as two new side bearings.What I'm trying to find out is what the pinions' pre-load shim pack should be.I was going to start with the original shims for pre-load,but with a new front bearing,figure that would change. From the Giulietta service manual(3)R/P BACKLASHDial indicator at flange set 45mm from pinion center.Lock ring.Rotate pinion right to left .006-.009".This corresponds to .002-.004"actual backlash.Your thoughts? (4)Lastly,housing to axle tube nuts,35-39ft.lbs.? Thanks very much,Phil D
 

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Phil, not to be negative but you said it was your "first time" on a RE. Personally I wouldn't touch it. I have rebuilt everything in the car myself but never a RE. It is a mysterious art of knowing what to do and look for and speaking with professionals who do it for a living even they don't like the process as it can be trial and error on the bench. I'd send it out to Richard or Besic if it is sick. It's not like we do these things more than once in our lifetime and the experience will pay dividends later. The downside is a noisy RE as a result will be a real downer. Just my 2 cents.
 

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Richard Jemison
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Rear differential rebuilding

divot is pretty well on regarding differential rebuilds.
You have about 1 chance in 20 to get a correctly spaced pinion even changing one bearing on it. If you use the rear bearing and shims and spacers and the pinion preload is correct when tightened you might get lucky. However you should not be changing bearings just because you think its time as all those bearings are very durable unless water was involved.

Commonly only wheel bearings need replacing and the LSD unit set up with correct clearances.

In any event set up the bearing preload in the housing before installing the pinion. Then you have to set lash after the correct total shim are on both sides of the Ring Gear carrier.
To maintain preload the total shim thickness of all the shims on both sides have to be maintained, Just add to left side shims to close lash while removing the same shim thickness on the right side and vice-versa.
 

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Discussion Starter · #7 ·
I know I'm asking for trouble,and I do appreciate both of you trying to point me in a more sensible direction,but some people just won't listen. I guess I just have to try it,I dunno.(I'm already shaking my head in disbelief) So if you both dump this thread,I will understand. Anyway,here are pictures of the pinion bearings,no water damage,pits,spalling,just normal wear so I'm told by a diesel mechanic.To my untrained eye,the front looks a little more worn than the rear?I've already ordered a front bearing,but if you can see enough in these pictures to tell if said bearing is OK and can/should be used(improving my chance of success)that's what I'll do.I haven't disturbed either of the cups or the pinion depth shim pack.Just have to clean,assemble with original pre-load shims,and check. AFA the side bearings,that's where I'm really asking for it. I'm using axle housings from a different rear axle assembly.(please don't leave yet!) I have new bearings ordered,or I could use the old bearings original to this R/P,this should be fun.But seriously,if I do my best and the unit starts humming,it shouldn't be too late for the ring and pinion to be set up by a pro,right? First pictures are inner/rear bearing and race.next post will have front.
 

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Phil, you haven't lost me and I haven't PO'ed you off. That is good. Since I never did this I'm just going to lay on my theory on why it is such a daunting task without the proper measuring devices and experience.

This is all conjecture...You mentioned replacing the housing.. well that's one of those machine parts with variations built in at the factory with tolerances that are taken up by shims in assembly.. thus the need of shims in the first place. If everything was perfect, there wouldn't be a reason to need shims. The gears (pinion and ring) are matched sets by the supplier (German) to finer critical tolerances yet.. and even they do it with trial and error to find the best combination before they stamp them as mated. So, I would conclude that reusing the shim pack in a replacement housing is really a crap shoot unless the housing is exactly machined as less than a curly hair the same as the one you are replacing and they aren't other wise the cost of the car would be so high it would never have any market. The 1 in 20 odds Richard cited become infinity to 1 now and you will need a shim pack that fits the housing not just the ones you took out of the first housing. How many shims and what size? Well consider the valve clearances in an engine and the wide range of shims needed. The engines leave the factory brand new with many many valve shim combinations because they take up the variations built in to the machine. It's just my take on the operation.

Now , I'll drop out and keep quiet. I always say don't fix it until it' s busted. I think that mantra applies to RE's.... U.
 

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Richard Jemison
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Diff build

With this project I`m afraid you are going to be severely disappointed.

I won`t assemble R&P bare units in a carrier. Good differentials are abundant.

If those were the bearings from the OE unit they look fine.

Why did you take it apart to start with?
 

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Discussion Starter · #11 · (Edited)
There was a lot of noise coming from the rear end,pinion seal was leaking,I needed to work on the silent blocks,and I wanted to clean up and undercoat that area anyway,so out it came.The wheel bearings were completely shot,but still noise coming from inside the unit.Took it apart and all bearings were history,along with a few chips out of both the ring gear and the pinion(all chips on the coast sides and out of the pattern area,not too bad and I was told that it could still be used).I had another complete rear axle assembly from a friend that said it was good,and now I'm confident that it is,so that's the one we are discussing and the one I'll be using.The problem is that the axle housings on this assembly need a lot of work.They're pretty pitted,the trailing arm brackets are weak and would have to be reinforced(I have the parts,but don't know how to weld,so have to be farmed out). On the other hand,my original axle housings are in very good condition cosmetically,and need very little work.So I figured that if the machined surfaces/cone seat measure OK,I could use them.No shims were used on either assemblies' mating surfaces,and so far,believe it or not,the right housings measure to within .001". I haven't pulled the left side cups yet,so if the planets are aligned properly I could get lucky(BIG "if").Otherwise I'll just have to go with the rusty stuff.I'm far from celebrating,but I'm getting ready.Hey Rick,I like the curly hair bit and your input,no need to keep quiet. Here are pictures of poor housings.Next post,much better housings and..
 

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The last picture pretty much sets me in the mood of the theme of this thread for me.. (hiccup)..... a fine blend of hops I have enjoyed in the motherland. As always, wujek ( google trans Polish)
 

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I happened to come across the pages in the shop manual that says it all.. (there are 7 1/2 pages! on this subject(... First SENTENCE says it all..."The correct operation of the differential and, in particular, the absence of noise, can only be obtained if the same procedure is adopted when assembling and overhauling as was used in the factory, and if the same checks and tools are used." That pretty much puts the RE repairs in the correct light.
 

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Richard Jemison
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Differentials

Differentials were not rebuilt or repaired by Alfa dealers, only replaced.
 

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I finished my 101 spider differential in January of this year and my 101 Sprint diff. March this year. we replaced all bearings/cones Let me tell you what a pita!!!, We (my Dad and I) struggled with the sprint more for no particular reason and it was the second one we did. I figured the second differential would have been easier!!! Each diff. required building and tearing down several maybe 5-10 times checking pre-load, clearances etc.. I had shims made in different thickness by a local machine shop. I also made my own out of .001 shim stock.. I can tell you it took several months of off and on hours to get it right. We did bench test both differentials for several hours on a 3 hp motor but the real test will be when I drive the cars.

And yes, the job would have been a lot easier with the correct tools! We had to make our own. I'll try to post photos.

btw, finding the correct bearings was not easy either....I got some from John Norman, Motion Industries and some from Classic Alfa.


Good luck!
 

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I finished my 101 spider differential in January of this year and my 101 Sprint diff. March this year. we replaced all bearings/cones Let me tell you what a pita!!!, We (my Dad and I) struggled with the sprint more for no particular reason and it was the second one we did. I figured the second differential would have been easier!!! Each diff. required building and tearing down several maybe 5-10 times checking pre-load, clearances etc.. I had shims made in different thickness by a local machine shop. I also made my own out of .001 shim stock.. I can tell you it took several months of off and on hours to get it right. We did bench test both differentials for several hours on a 3 hp motor but the real test will be when I drive the cars.

And yes, the job would have been a lot easier with the correct tools! We had to make our own. I'll try to post photos.

btw, finding the correct bearings was not easy either....I got some from John Norman, Motion Industries and some from Classic Alfa.


Good luck!
I know Besic would concur on the multiple teardowns.. It was what I referred to as "trial and error" in a previous post.
 

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Guys:

I've done three 115 differentials - two were successful. I do have the Special Tools and a complete set of shims. It's still a nightmare job to do. I tore each assemblies down, trial and error, not less than twelve times. My niece walked by my differential stand once and said "When are you going to finish that" referring to the half of rear end mounted there more than two winters. I want to discourage anyone from undertaking this project if you can find a second rear end. If I get time , I may undertake overhauls for patient people in the future; For Money! I just don't need the money bad enough now.

By the way, the first differential I undertook ground itself to death in a few summer months.
 

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Yep, no doubt a PITA! I did not enjoy the long painful process. Patience is so important here... I think if we did enough they would get easier to do.
 

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Discussion Starter · #20 · (Edited)
Just now able to get back to this project.I'm waiting on a local mechanic(he's away til' Monday) who I was referred to by a machine shop close by.He supposedly builds cars along with doing differentials for the racers around here.But unless I'm talked out of it,I'm going to use the complete pinion assembly as is,seeing that the bearings are fine,per Richard.So shouldn't have to set pinion depth.AFA using the cosmetically much better donor axle tubes,I'm gonna wait until I show them to this mechanic/car builder.I've measured the machined surfaces of both the rusty axle housings/tubes and the good ones,and they're within .001-.002" of each other.That's measured on the center section side of the tubes,I didn't measure the total length of each tube yet.To be honest,I'm not sure what the axle tube flange shims adjust(neither assy. had any)but I assume it has to do with wheel centers/total length of axle assembly,hub to hub? I have new SKF side bearings,but the old ones may be good?;the pinion bearings are. Hud,can you tell me what method you used to set preload on both pinion and ring gears,and what values you ended up with? Did you measure backlash at the pinion flange,what did you end up with? How did all of this work out in real driving? Left and right carrier bearings as pictured.They don't look as good as the pinion bearings to me,your thoughts?Better pictures,different angles? Thank you all,Phil D
 

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