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Discussion Starter #1
I asking to find out there is a short cut to estimating the thickness of the shim(s) that has to be installed between the gears to give the 42 -42.2 mm clearance or is it just a process of trial and error until you get it right? How critical is this measurement?



When changing the bearings and mixing gear sets, you have to start somewhere.

Also where is a source for these shims?
 

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Is there an easy way to determine shims required?

I'm asking to find out there is a short cut to estimating the thickness of the shim(s) that has to be installed between the gears to give the 42 - 42.2 mm clearance or is it just a process of trial and error until you get it right? How critical is this measurement?



When changing the bearings and mixing gear sets, you have to start somewhere.

Also where is a source for these shims?
Hi Christopher,

Did you ever get an answer to your questions above? Obviously not in this thread, but elsewhere perhaps?

Correct me if I'm wrong, but isn't the shim location between the 1st gear bushing/sleeve flange and the inner race of the intermediate mainshaft bearing the one that ultimately controls the 42mm - 42.2mm distance between the 3rd and 4th dog gears? So adding or removing shims from between the 1st gear sleeve and the intermediate bearing is what changes the 3rd to 4th gear distance, right?

Like you did, I am mixing and matching parts from two different gearboxes. So while I did count and maintain the number of shims between the 1st gears and intermediate bearings on both, I can't default to either shim setup on the rebuild.

And there in lies the rub - if the intermediate mainshaft bearing is pressed onto the shaft, and the distance between 3rd and 4th is not the required 42-42.2mm, that same intermediate bearing has to be pressed back off, and the number of shims adjusted, correct? Seems like a real pain.

If that shim (or shims) between the 1st gear sleeve and the intermediate bearing is what controls the 42.0mm to 42.2mm spacing between 3rd and 4th, then after installing both the 3rd and 2nd gears and their associated hubs on the mainshaft, couldn't one just slide the 1st gear sleeve up against the 2nd hub and measure the overall distance (from outside the sleeve flange to where the mainshaft contacts the input shaft)? Then put the input shaft and the intermediate bushing into the case (without the mainshaft) and measure the space between them, and thereby "back into" an approximate required shim height?

It seems if you measure everything carefully and do the math correctly, you might be able to get the necessary shim height within +/- 0.1mm so that when everything was torqued down you would still be in the 42.0mm to 42.2mm range. Theoretically, I mean.

Anyway, I would love to hear if there is an easier way to get the distance between 3rd and 4th correct without a bunch of trial and error pressing and unpressing of the intermediate bearing.

Of course if that's the only way to do it, I can deal with it, but it sure seems like someone would have found an easier way by now.

Thank you kindly,
 

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Discussion Starter #6
Possibly a Better Explanation of measuring?

I would like to believe this is a better explanation of the gear measurements. Please correct me if I am giving out wrong information here.

I was putting the transmission together and analyzing what the 42.0-42.2 mm measurement means and how it comes to be. Lets say for the sake of the discussion that the rear main bearing (closest to the reverse gear) is considered 0 (zero). The front bearing which carries the 4th gear and caged bearing is also considered to be 0 (zero) as it is fixed in place by the bearing it rides on. So what is the variable? It has to be the shims under the rear bearing that adjusts the "main shaft" forwards towards the 4th gear or backwards towards the reverse gear.

The optimal shim pack is variable to achieve the aforementioned clearance in thousandths of a millimeter. If you come in under 42.0 you have to reduce your shim. If you are over 42.2 you have to increase your shim pack.

I came to understand that the caged bearing that rides on the end of the shaft has to have a optimal distance inside the 4th gear housing. Anything less it isn't carrying enough load, and anything more it is being compressed into the back of the 4th gear. This distance creates what I would call a minimal load.

The factory manual does not do a good job of showing what is measured, so I have attached a quick grab photo with marks to show where to measure with your calipers.

 

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a few more stupid questions...

Are shims used anywhere else than between the 1st gear carrier sleeve flange and the intermediate bearing on the mainshaft?

The 105 Gearbox Manual talks about using shims to take up any end play between the direct drive shaft and the 3rd-4th gear hub (which is pressed onto the output/mainshaft), but it doesn't indicate where to install those shims if they are needed.

It also states that the end play on the mainshaft gears should not exceed certain limits, but it doesn't explain how to correct that condition. Do more shims get added next to the 1st gear to fix that, or are the gears themselves supposed to be replaced?
 

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Discussion Starter #8
The only place that I know of is between the bearing and 1st gear. There are shims to be placed under the 4th gear input shaft that keep the bearing from moving back and forth. They go under the lock nut/snap ring. The bearing goes on then the shims.

You are correct, it doesn't say how to take up the end play.

Part of tearing down the trans is to look at all the gearssliders,synchros, the shaft, bearings, in side the gears and the condition of the shims as well as the main bearings. Anything suspect is replaced. Considering how long it takes to R&R a trans, tear down and rebuild, best to put in the good stuff and not worry about reusing the old stuff. It is not a cheap proposition to rebuild a gear box back to new standards.
 

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Hi Christopher,

Thank you for the outstanding advice. Here's what I will be replacing with new parts:
1. The bronze bushings in my 1st, 2nd and 3rd gears (the IDs of the old ones were between 0.004" and 0.008" over the shaft ODs)
2. The 4th and 5th needle bearings.
3. Intermediate bearing.
4. Rear bearing.
5. Dog gear on 2nd.
6. 2 of the synchro rings.
7. 2 of the synchro sliders.
8. And maybe the input bearing and 4th gear bushing.

The rest will be made up of the best parts out of the two gearboxes at my disposal.

I've just got a couple more questions for you (or anyone else who's been down this road):

1. When you did your rebuild, did you install everything on the input and mainshaft (including the giubo spider), torque the output nut to 87 ft-lbs., measure the "A" distance and then take everything back off to install the correct number of shims? - or did you just get lucky and manage to have "A" measure between 42.0mm and 42.2mm the first time?

2. Does everyone who rebuilds a gearbox, and mixes gears from other boxes, have to press it all together and then un-press everything (except 2nd and 3rd hubs/gears) just to add or remove shims?

3. As far as you know, it's not possible to check the "A" distance without adding everything aft of the intermediate bearing (reverse and 5th gears/hub, rear bearing, flex coupling tripod, and nut)?

Thanks,
 

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Discussion Starter #10 (Edited)
Norseman, I just finished building 3 more gear boxes from mixed and best parts. The first shaft I just grabbed a shim from the available ones that I have from the gearboxes and a small stash of new ones. I got lucky as it came to be measured at 42.2 mm. So that went went together easy.

The shims I measured were in the range of about .008 -.009 mm that I installed the first time. I kept this as a standard so I would know which direction I needed to go if I had to replace one of the shims.

The 2nd shaft was grab one from the stash and build it up. It measured also at 42.2 The 3rd shaft came in way over 42.2 mm to around 42.3-42.4 mm So I took the shaft apart down to the shim, replaced it with a thinner one and put it together. Measured and it was over 42.4 mm. I realized my mistake, took the shaft apart again, and inserted a shim that was twice as thick as the first one I put in (about .020") . The shaft measured 42.18 mm. I was finished.

Just know that you only have to remove the nut, splined shaft, rear bearing/or race depending upon the trans you are building, the thick washer, 5th gear with race/needle bearing/, slider hub, reverse gear and the main shaft bearing. You can safely pull all of that off with a press by using the device to hold the reverse gear in close. The stack just pulls off easily if you lightly greased the shaft. Remove the Woodruff key, pull main bearing and swap shims. Then you put it all back together.

I am not sure how people put the slider hub on, but I have used a very hot sun in the afternoon to expand the hub, but since it isn't that hot yet, I just use my propane torch to heat it, and with some pliers drop it into place. Some times it takes some gentle tapping or the use of a long narrow pipe to tap on, to make it slip on.

5th gear fork has to be installed after the case is bolted together. When you install the 1/2 and 3/4 shift rods install the ball bearings and springs and caps to hold the rods centered. Remove to install the 5th gear rod then reassemble. Don't forget the lock washers on those bolts/nuts.

Just another note, don't forget to install the 3 pellet shaped locking bearings into the holes before installing the shift rods. A long pair of needle nose pliers, some white grease and a small screw driver will make this an easier job.

If you are building a 1300/1600/1750 split case you will have to replace the rubber o-ring shift rod seals in the case or you will get leakage.

Other than the shim adjustment, these are fairly easy gear boxes to work on. The synchro covers are a royal pain, but get the cir-clip pliers I recommend in another post i have here, and use with gloves. The rings come off and go back on with some effort. The gloves make a huge difference in how much gripping force you can apply with your hands.

Measure the centering of the sliders...it is about 4 mm on both sides to center it. Tighten the lock bolts, remove the shaft, tighten and bend the lock tab. Reinsert the shaft and then the counter shaft.

I hope this helps people understand more about this transmission by sharing some of the things I learned along the way of building up 4 gear boxes. It has been over 25 years since I rebuilt my last one so it was a "relearning" experience.
 

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Hi Christopher,

Once again your knowledge is extremely helpful, and your presentation/descriptions are very easy to understand. I read and re-read your last post until everything made sense. It's just great.

I'm sorry to continue to trouble you, but I'm hoping you won't mind clearing up a couple final questions.

The first shaft I just grabbed a shim from the available ones that I have from the gearboxes and a small stash of new ones.
Where did you manage to find new ones?

The shims I measured were in the range of about .008 -.009 mm that I installed the first time.
Although you indicated you were referring to millimeters here, didn't you actually mean to say you found your shims to be .008 -.009 inches thick?

The 3rd shaft came in way over 42.2 mm to around 42.3-42.4 mm So I took the shaft apart down to the shim, replaced it with a thinner one and put it together. Measured and it was over 42.4 mm. I realized my mistake, took the shaft apart again, and inserted a shim that was twice as thick as the first one I put in (about .020"). The shaft measured 42.18 mm. I was finished.
Thank you for this tip about adding shims to reduce the "A" measurement! I would certainly have done the same thing you did the first time, so this advice is very helpful!

Just know that you only have to remove the nut, splined shaft, rear bearing/or race depending upon the trans you are building, the thick washer, 5th gear with race/needle bearing, slider hub, reverse gear and the main shaft bearing.
The second item you mention here, the "splined shaft" - are you referring to the spider tripod that slides onto the output shaft splines and bolts to the giubo flex propshaft connector?

The synchro covers are a royal pain, but get the cir-clip pliers I recommend in another post I have here, and use with gloves.
I did exactly that, and found the Lang Model 75's make the job almost manageable. I ended up ordering a second set of the .090" diameter tips, since the repeated removal and installation of the clips during synchro dis-assembly and dog pressing kind of beat them up. And the use of gloves really does help.

Besides the gearbox that came in my 1988 Spider (which I have dis-assembled) I found 3 used gearboxes ('84, '86, & '87) for only $600 (total), so I dis-assembled one of them (the '86) for donor parts in my rebuild.

Even with an entire donor box of parts at my disposal, I decided to buy 2 new rings, 2 new sliders, 3 bronze bushings and 3 bearings (I don't want to be pulling this gearbox again soon).

If the darn parts would ever get here from Germany, I could start my re-assembly!
 

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Discussion Starter #12
Norseman, I sent you a PM :)
I did mistakenly say .009 mm when I really meant, .009 thousandths. Sorry about that.
Christopher
 

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You can probably get some shims from Larry at Alfa Parts Exchange in California, but what is your "A" measurement currently at?
42.65
You will probably need two or three shims, depending on the thickness you get. As I recall, there are thick ones in the 0.02" range and thin ones that run in the 0.008" or 0.009" range.
Give Alfa Parts Exchange a call. Larry probably has some and can easily drop them in an envelope to you so the shipping cost will be nominal.
 

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I agree with most everything here, add a few thoughts

1. When measuring the A distance, both side nuts on the shaft must be torqued to spec. Also, the mainshaft should be lying in the half shell, with the input shaft and rear bearings properly seated. Its really easy to get a little piece of crud in the input bearing groove and when that happens, you will not get repeatable A measurements. SO spend extra time with a Q tip to absolutely clean that groove (and really all bearing mounting areas) with brake cleaner.

2. Misumi USA sells custom shims. I agree with calling Larry at APE. Enjoy the conversation with Larry he's a really fun guy to talk to !

3. Do not make first gear bush (or any of them for that matter) too tight! Ask me how I know. 0.002 - 0.003 " is the range you want and dead true to center AND dead perpendicular.

4. 20 ton press is the way to go, but I';ve done just like Chris and used my propane torch to heat up the tripods and slip em on.

5. If there is ANY scoring of the shaft, polish it completely out with 2000/2500 grit paper. Even a half thou ridge or scratch on the shaft will make your life miserable.

6. Always, always, always replace the single and double row needle bearings. (5th and shaft to shaft)

7. Always measure input shaft front bearing. If its worn, replace it. Its expensive but so worth it.

8. Use assembly lube everywhere except on synchro rings.

9. Make certain shift forks are centered in sliders with rods in detent neutral, and sliders centered over tripods. I use two sets of feeler gauges on both sides to set the center.

9. Fix it right the first time. Don't skimp on parts or labor. When the box is rebuilt to a high standard, its amazing. Shifts up and down like butter.

Measurement of rotating parts (bushings, bearings, etc) is critical. if the bearing feels or looks worn, replace it. There are 5 bearings in the trans (3 main, 2 layshaft). Check them ALL for runout/abrasions etc.
 

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Answers to the points below:

1. Yup, I torqued the nut on the output flange side to spec (86-87 ft*lbs). My transmission has circlips on the input shaft and 3rd gear end of the mainshaft. I am going to give eveything a good cleaning, and try again.

2. I'll call up Larry...he delievered my 2.0L motor core to my house personally! Great guy!

3. I told my machinist to give 0.002" clearance diametrically (so .001" wall to wall). Shane over at Foreign Machine Service in Pasadena did the work...great shop, always some obscure motor or something you've never seen before lurking just behind the counter that he is working on. The gears are a little tough to get centered on the shaft, but once they are, they slide on real smooth, and turn with no binding. They don't exactly freewheel on the shaft when turned, but it is nice and smooth, with no laterally play detectable by hand.

4. Yup, exactly what I did. Harbor Freight 20 ton press, tripods heated then dropped into place.

5. The machine shop polished the shaft while he was doing the bronze bushings

6. Replaced!

7. I replaced every bearing. I was on the fence about this, but then though why skimp out now when I have the whole thing apart?

8. Assembly lune I did not use, but I used the Redline 75/90 NS oil. Should i redo it? Since I have to get back in there and add shims?

9. Not there yet, but I'll remember that!


Thanks for the help!

-Andy

I agree with most everything here, add a few thoughts

1. When measuring the A distance, both side nuts on the shaft must be torqued to spec. Also, the mainshaft should be lying in the half shell, with the input shaft and rear bearings properly seated. Its really easy to get a little piece of crud in the input bearing groove and when that happens, you will not get repeatable A measurements. SO spend extra time with a Q tip to absolutely clean that groove (and really all bearing mounting areas) with brake cleaner.

2. Misumi USA sells custom shims. I agree with calling Larry at APE. Enjoy the conversation with Larry he's a really fun guy to talk to !

3. Do not make first gear bush (or any of them for that matter) too tight! Ask me how I know. 0.002 - 0.003 " is the range you want and dead true to center AND dead perpendicular.

4. 20 ton press is the way to go, but I';ve done just like Chris and used my propane torch to heat up the tripods and slip em on.

5. If there is ANY scoring of the shaft, polish it completely out with 2000/2500 grit paper. Even a half thou ridge or scratch on the shaft will make your life miserable.

6. Always, always, always replace the single and double row needle bearings. (5th and shaft to shaft)

7. Always measure input shaft front bearing. If its worn, replace it. Its expensive but so worth it.

8. Use assembly lube everywhere except on synchro rings.

9. Make certain shift forks are centered in sliders with rods in detent neutral, and sliders centered over tripods. I use two sets of feeler gauges on both sides to set the center.

9. Fix it right the first time. Don't skimp on parts or labor. When the box is rebuilt to a high standard, its amazing. Shifts up and down like butter.

Measurement of rotating parts (bushings, bearings, etc) is critical. if the bearing feels or looks worn, replace it. There are 5 bearings in the trans (3 main, 2 layshaft). Check them ALL for runout/abrasions etc.
 
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