004 Rebuild

[raygreenwood]

let me see if I canconsolidate that last post a little. Its hard to do from memory in a hotel room

What you are trying to do: The differential has three critical tolerances inside (actually more...but three we can do something about)

A lot of wear and nastiness gets started when either:

(a) the outer shims...those split rings between the CV flange and the diff body...either get worn out or messed up some how. It hammers the side shafts in and out...sometimes messing up the flat shim inside that is between the side stub axle and the diff body inside. This is the flat shim dead opposite the split ring we are talking about.

(b) or....if somehow the spacer tube inside of the diff..that keeps the two side shafts from sliding too far in...gets worn or damaged.

So in short...we are trying to keep the side sstub axles from moving too far in or too far out. If they do either...it wears the gears and spyders and will eventually break them.

In your tranny...you have already found that the outer split shims and CV hubs are nice and tight. That means that the inner flat shims aree probably fine as well.....but to be sure you need to measure the gap at those outside shims...if any is there. Check the bentley manual for proper tolerance.

If the inner spacer tube gets worn....it can allow to much inner movement which is what wear the other two shims.

If all of these things check out and there is no spalling on the spyder teeth....you can reassemble the diff and we can get on with the transmission.

If the sypder teeth are worn or chipped..........this becomes a totally different conversation.

They fit nothing else....and the differntial housing is totally unique. No other ACVW has a diff that will fit in this case.

BUT....there is a high chance that we "could" use the sideshafts, spyders, spyder axles etc.....from another diff.....if we remachine the diff housing. Its something I'm working on. Ray

[Bill K.]

This is a great topic!

Thank you. It's the first time I've been into a transmission. With Ray's help, it's going well and is more straight forward than I expected.

[Bill K.]

Ok...the differential. Its easier to work with of you go ahead and pull the bearing off the long end so you can lock the diff in a soft jawed vice. You pon't have to lock it hard.

Before you take it apart...you need to read up in the brown bentley typr 3 manal...or any Bentley ACVW manual....about measuring the play in teh differential side shafts.

Just going from memory ...you first lock one side shaft in a vice so you can lift upward...to pull the stub outward...so the gear head on the inside comes up tight against the shim underneath. Then....you can pull/move the opposite stub axle in and out to measure any slack or movement with a dial indicator. This will tell you if the stub has slack between it and the shim or it and the spacer tube.
Then you flip the differential over and measure the same on the other stub.

To have teh stub axles in te hcorrect position to measure the stub opposite....I beleive you will need to put teh outer spacer ring back on...and reinstall the CV flange on oneside at a time..to set the spacing correctly...so you can measure the slack on the other side. I am going off memory on this method...so check the book method.

I can tell you this much already. Since the shim ring on the outside of the stub axles was tight between the diff body and the CV flanges....its an excellent bet that the shims inside....those under the gear head of the side shafts between the gear head and diff housing.....are NOT worn significantly.
So....any in/out movement of the stub axles....will denote wear of the spacer tube inside of the differntial. That is...IF the amount of slack or movement you find.....is excessive according to the book.

The reason you need to measure both sides in this manner is because one side may have moe wear than the other.

It really should be pretty simple.....once the outer spacers and CV flanges are installed....you either have correct slack between spacer tube and side axles or you have excessive slack.

The differential end play is zero as far as I can feel by pulling/pushing on the side shafts. I don't have a type3 or bentley book, but I see the general idea in my type2 factory book in the 091 section. The spec in the factory book is 0-.14mm. This one is less than .005" for sure.

To disassemble the diff.....you need a brass drift and a rubber mallet.

Mount the diff in the vise....marke the cover position and gear location.....and loosen all the bolts. Screw them out a few turns each...then whack them with a rubber mallet. This will start pusing the gear off.
When you get it far enough out from the diff body to get a thin brass drift between gear and cover...stop whacking on the bolts.

You want to first remove one bolt all teh way so you can see how deep it goes into the gear. Reason why....is you do not want to whack on bolts that have less than 5-6 threads into the gear....so they have enough load surface that you do not damage the threads.

Removing gear with punch

When the gear is off....the cover comes off. You can see taht there are two holes on the inside of the cover to allow you to use a puller/drift/punch..to drive off the short side bearing.

After splitting cover from housing with chisel, here's bearing removal from cover

Short shaft differential gear and mating surface of shim

Cover and mating surface of same shim

Differential housing with spyder gears, spacer, long shaft diff gear

The spyders are tight

Let me know when you get to this point. You want to see how much side to side slack the spyder have on their shaft. Then you can remove the roll pin...and drive out the cross shaft. Ray

[Bill K.]

Back a few steps regarding the pinion bearings...

........ Now you can push the pinion carrier and shaft out from the inside.

Make serious note here:

When you buy new pinion bearings...do not do so until you have the old ones off. You will need to do this in a press with proper pullers at a shop.

The reason is.....and I made this mistake.....the bearing that is on the pinion shaft is available in TWO identical part #'s...with different letter codes. The different letter codes denote a different filet radius on the bottom side of the bearing. One works...the other does not.
DO NOT buy bearings until you have the bearing off to read the EXACT part #.

......

I was able to remove the front outer pinion race with a punch and a little heat, but the inner race is very tight and will require a trip to AA Transaxle in Monroe, WA. for help from pro's with the right tools and experience.

The bearing is worn

[raygreenwood]

Oh yeah! You are a lucky man. The syders, gears and shims are in great shape. Just reassemble it.

Yes....you have to have a thing edge bearing puller and a press to get the pinion shaft bearngs off. Be carefull to support the shaft with something soft in case it drops.

Once you get the bearings off....make note of the part #'s and buy them.

I then polish the bearing areas with 2000 grit to make sure there are no burrs. Make sure when pressing the new bearings on....that is the yget cocked even the slightest bit....STOP...remove it and repolish the shaft. These shafts are very hard. Trying to correct a cocked beaing with force will NOT work.

let me know when all of the bearings are re-installed and we will go through adjusting.

The one tool you will probably need to buy.....and trust me on this...it will be useful....is a beam style inch/lbs torque wrench. We will be installing (a) a spinner handle on it so you can rotate it qucikly and (b) a small piece of graphite "lead" like you use inj a mechanical pencil....so while rotating the wrench ...the requisite max torque in inch/lbs gets recorded on teh scale in pecil line on a stip of tape....so you don't have to watch the beam while yo work. Its the cheapest way to go and accurate.....and you will also use this wrecnh whenever you install and adjust the rear wheel bearings. Ray

[Bill K.]

The one tool you will probably need to buy.....and trust me on this...it will be useful....is a beam style inch/lbs torque wrench.

Will do. What range and precision?

[raygreenwood]

Look in the haynes manual. See what the range of the adjustment of teh rear wheel bearings need to be.
Then...look in any of the haynes or bentley manuals. See what the range of tolerance and torque needs to be in setting up preload on differntial side bearings. Get one that can do both of these.

There is also another way I am thinking may be easier....and I have done it before and it works. Its just hard to explain.

We are talking inch punds here. One ft/lb is 16 inch pounds. Make an adaptor to use one of your CV flanges to grip the side shaft. Then get a length of 1/2" rod. Cut it to exact length...find the balance point dead center. Mark the rod in exact 1" encrements. The shaft needs to have its balance center found so that when you have the rod attached to the diff shaft and its dead horizontal...the rod will stay stationary.

The object with the dynamometer they use in the book is to first oil the bearings with the exact oil you will be using.....then at a reasonably known temperature in the room...spin the bearing shaft a set number of times at a trackable speed...like one 1/thousand...two one thousand...etc.

This shears the oil and gets it uniform in viscoisty and gets rid of excess. Then quickly stop your rod/gauge at exact horizontal and clip on a one pound weight at one of the inch marks. If you are out at the 16th inch mark...that is 1 ft/lb. Let go of it quickly. If it just starts to turn the shaft by its dead weight alone....you are done.

Example

So...if the bearing preload setting is say...10 in/lb.....oil the bearing. Clip the 1lb weight on dead center on the 10" mark on the shaft. This is 10" from dead center of the differential side shaft. Spin teh shaft say...25 times at 1 rev per second.....one 1/thousand...two 1/thousand...for 25 seconds. Stop at dead center with shaft horizontal and release the shaft. Doesn't move?....too tight on the side adjusters. Move too quickly...too loose.

You can also do this with a "fish scale". This is how Saab does it. Ray

[Bill K.]

Look in the haynes manual. See what the range of the adjustment of teh rear wheel bearings need to be.
Then...look in any of the haynes or bentley manuals. See what the range of tolerance and torque needs to be in setting up preload on differntial side bearings. Get one that can do both of these.
...

You can also do this with a "fish scale". This is how Saab does it. Ray

In the Type2 Factory book, the 002 differential bearing turning torque (preload) is specified as:
New bearings: 26.0-30.5 in lb
Used bearings (>30 miles): 2.7-18.2 in lb

I like the "fish scale" approach.

BTW, I'm working with a Thanksgiving tranny, made Nov 23 1973 (thanks Fye)

[raygreenwood]

The only problem with the fish scale method...is that there is only one way to do it properly. You cannot simply tug on a beam (like with the rod I mentioned)....or use it to pull on a torque wrench. The problem is that there is no way to calibrate how much force you use to start pulling on the fish scale while taking up slack. With the small amount of inch/lbs we are using....it will be highly variable and inaccurate.

The way Saab gets around this......is to take a correctly calibrated fish scale....and its not just a simple scale......and a length of non-stretchable, non-elastic smooth cord. You wrap the axle or shaft extension with a smooth wrapping of cord to get at least 12 full revolutions...and use a weight attached to the other end of the fish scale...with a dropping mechanism...instead of your hand.
Then..convert from rotational force to newtons...to ft lbs.... ...jeez...I have it written down as per the scale I used somewhere. It does work very well.....but is just not worth the hassle.

Originalyl...I tried a very fine in/lb click type torque wrench with a spinner knob installed. Highly variable...again...because of the low tolerance and variable onset of torque by my hand.

What you need...is a mechanism to lock the wrench....so you can get your revs up to standard spinning the shaft while you then unlock the wrench...and measure the rotational drag/force....and then convert to inch/lbs.....and I do have this formula.

It really is best to get actual inch/lbs direct with the shaft method....in my opinion. At least I could repeat the adjustment three times in a row using the shaft method. Ray

[Bill K.]

Once you get the Torlon bearings made....I am working out the drawings of the mods to make to them to greatly enhance the oiling.....and to pin them in place. You will need a dremel tool to accomplish teh final mods...but they are simple .

basically....you will be (a) sanding a 45* bevel on the ID of each end of these bearings (5) at low speed will a high speed steel ball cutter you will be installing two grooves...180* apart inside....each one only half the length of the bearing ID...and from opposite ends. The end that will go to the inside of the gear cluster.....will also get a triangular "ramp"....that intersects both the ball milled groove and the bevel at the opening.

What this does......is as the bearing (which will be connected to the gear with a pin)...turns around the 18mm shaft.....the triangular ramp scoops oil at an angle....rolling it into the ball milled grovve to keep thing lubricated. The ramp from the opposite end does the same from oil brought in by the three slots you grooved into the shaft faces. Keeping the oiling grooves in teh bearing at 180* apart insures that the oil will not just pass through teh bearing without getting spread on the shaft.

I have found that teh oiling grooves at each end of the gear...along with drilling the center oiling hole larger by about 1.5 mm....and scaloping the leading edge twoard rotation....of that hole...greatly helps the shaft to be submerged in oil inside. This helps a lot even with needle bearings. With modified Torlon plane bearings the lube will be much better. Ray

Ready to machine bushings...
1. ID +.0010/.0015 clearance with countershaft
2. OD -.002 interferance with counter gear cluster bore
3. Pin inside end of bushing to counter gear bore bottom
4. Groove ID of bushing 1/2 length, 180 degree separation
5. Groove outside end of bushing from OD to ID groove at angle
6. Length of bushing equals needle bearing bore depth (end of bushing flush with end of counter gear)

Ray, please verify 1-6 and clarify #4 for groove width/depth and #5 for width/depth/angle. A sketch would be nice... Thank you.

[raygreenwood]

I will try to make a sketch tonight. Hang loose! Ray

[Bill K.]

Great - thank you.

I went to AA Transaxleand met the owner, Daryl. He's a synchro specialist and was interested in the 004 having never rebuilt one in his 30+ years of VW mechanics. He made quick work of removing the pinion and diff bearings. It's not so much that he had special tools, he just knew how hard to hit and when to stop before breaking something

The pinion bearings were removed and found to be different heights. The rear inner race is .030 taller than the front. I have found sources for the front inner (Timken M86648A) and outer race (Timken M86610) as well as the rear outer race (FAG M88010) but I cant find the taller rear inner (FAG 529593). Other than the height, the front and rear inner races appear to be the same. Can I use another shorter front inner race in place of the rear with a shim?

[raygreenwood]

Ok...so on the bearing at the bell housing end (where the 5 hole shim is) you can't find the outer race? Take your time on this....look around for the correct one. I have some bearing sources if you need them.
But yes.....if its a hard and very flat shim....you should have no problem. Don't just go off of the measured height of the race though....to get the difference. The best way to get as close as possible is to reinstall the old race...oil the old bearing...set the bearing into it flat and use a dial gauge and block or a long armed vernier caliper to measure it....then repeat with the old bearing and the new short race..... to get the height difference. Ray

[Bill K.]

Ok...so on the bearing at the bell housing end (where the 5 hole shim is) you can't find the outer race? Take your time on this....look around for the correct one. I have some bearing sources if you need them.

I can't find the inner pinion race for the bell housing end (rear). This is FAG 529593. I've searched, emailed, and called without success. Any bearing sources you have would be appreciated.

[raygreenwood]

Try Purvis bearing in Dallas. 214-358-5588. They are hooked up through many national chains. You will want to have them cross match to Timkin most probably. It will be ok to use the shorter race with a shim....but we will just have to be exacting in what we do. The pinion races and bearings are responsible for setting the pinion to ring egar relationship. If that gets changed its not good. Ray