Bronze gear bushing clearance - Page 4 - Alfa Romeo Bulletin Board & Forums
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post #46 of 70 (permalink) Old 07-21-2016, 05:57 AM
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post #47 of 70 (permalink) Old 12-19-2016, 06:15 PM
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Bob,Did you ever start/finish your second trans? I'm having to do mine over because of noise and a tight spot/binding in 2 and 3.I tried doing my own gear bushings(dimpled,split type)and think I got them off-center. I do believe I nailed the [email protected] .0015" to .001" with nice slip fit and no wobble. FWIW,I found grooved bushings at Afra.it. and thought I'd give em' a try this time.They look similar to yours and pretty well made,(the oil grooves could have been machined a little better or cleaner,but that area will need to be honed anyway).They're close,but not a slip fit over 1,2,or 3.I tried fitting inside an old gear,but not close to a push/drop in.Possibly a different maker?? Just thought I'd pass this along and touch base.Regards,Phil D
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post #48 of 70 (permalink) Old 12-20-2016, 07:54 AM Thread Starter
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Hi Phil

My trans is sitting on the garage floor waiting for the car to be ready to install it. Floor pans first undercarriage clean up and engine bay paint touch up then front suspension. Question -- does this issue happen only when cold or all the time ? I assume the trans is installed in the car, correct?

I would think that if you were offset enough to cause binding or wobble you would have seen or felt it. Cant help but wonder if its something else causing it and not the bushes-- Richard J advised someone before that had bushing 'too tight' issues to drain the redline 75-90NS and run 30 weight motor oil for a little while (this is second hand info so not sure of the details) -- apparently this worked well and 30 miles later no issue

Suggest you ask Richard (alfar7) on this board I'll bet he has some wisdom to consider

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post #49 of 70 (permalink) Old 12-20-2016, 09:29 AM
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We did feel it.I was working on this trans along with an experienced Alfa mechanic.I wanted to do the gear bushings myself,so when I was done,all parts went to him to assemble the trans,(all new shaft and needle bearings,gear bushings,moly syncros,)to make sure that everything was shimmed right,forks centered,etc..I wasn't there during assembly so he called me and said that there was a bind in 1,2,but also thought trying it as is might clear up the problem,really not sure(Richard thought so too).I brought it home assembled,put it on the bench,added "3"qts.Spirax 80/90,put a clutch disc on and turning by hand,binds "tight" in one spot on 1st,2nd,somewhat 3rd.gears. Hooked up a motor to it on the bench,spun it for probably 5 min. at a time,maybe 20 times.Seemed a little better(BTW,Richard said spinning with no load does nothing AFA breaking in) Drained oil,much yellow powder suspended in the green/gold oil.I did mention the bind to Richard,said to go ahead and try it,but in fairness,my bind and Richards bind are no doubt two different things.Now added correct amt.Amsoil 75/90 .In the car,clutch in,quiet,clutch out really deflated me;way too much noise(in neutral too),like bearing noise,worse than before rebuild.Driving cold,"very hard" to shift,gets better warm,but still unacceptable.I trust the mechanic,he's done a zillion of these,and asked him if he noticed a bent shaft,shift shafts,forks,but he didn't and believes my bushings are off. I have lightened gears,first gear fix,appx.2K mi.on other moving parts,sliders,dog gears,straps,quadrants,you name it.One thing struck me funny;it's not too hard to physically downshift,but absolutely "no" grind at all,falls right in. I could go from 3rd to 2nd at 50+mph(I didn't do it),no problem. All in all,mechanic feels that the gears "****" on the shaft and will not mesh properly with slider/syncro...Not such a quick replySorry to all,this should be a PM
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post #50 of 70 (permalink) Old 12-20-2016, 09:46 AM Thread Starter
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If you get the noise in neutral I would probably suspect the mainshaft bearings not so much anything associated with the gears themselves. So sorry to hear about this Phil -- I think your approach is a good one, pull the trans and open er up. I realize its a hassle but if you are anything like me, once you get started (ie get over the 'stay at rest inertia) I suspect you will actually enjoy finding and fixing this! Its a couple of weeks work -- And I think this thread is the right place for this as others may learn from this -- I am really curious to know what you find --

bob

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post #51 of 70 (permalink) Old 12-20-2016, 10:51 AM
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Bob,Thanks for the encouragement,and approval AFA where this reply belongs.Yes,once the trans is on the bench,I'll enjoy the surgery.Being 69,alone,and on my back,R&R is not so much fun.I believe that I have more than one problem going on here.(First is I don't know *** I'm doing!)..Bearing type noise should point to bearings,but none are sealed so visually not defective and all new(unless something got mixed up during assembly,). Very hard shifting,who knows,til' it's opened up.Could be several things,including something trivial in the shift tower,but the gold/green oil evidence points to something else.Something important that I forgot to mention is that I could have gotten some moly/non-moly straps and quadrants mixed up in a syncro assembly.I had both types of transmissions opened/dismantled at the same time.I "really" doubt it,but **** happens. Question to all:Can you feel a problem in an incorrectly assembled syncro/gear assembly,such as non-moly straps/quadrants in a moly syncro assembly,or does the assembly have to be dismantled,or compared with a known to be correct assy.,or?? Trans is still in the car,and with holidays,might be a while,but I promise to keep you posted.Best Regards,Phil D
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post #52 of 70 (permalink) Old 12-20-2016, 11:25 AM
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Hi Phil,

I picked up a AROC Competition Advisory Service book. AROC did this in 1970. I believe it was done in conjunction with Alfa of North America. I'm thinking Don Blacks Green Competition Reference Handbook evolved from this. But until I see one Don's books I'm not sure.

Anyway I noticed the pages in the book and it looked like some copy's from somewhere you had. But thought I would post some pictures of the originals.
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1969 1750 Spider Veloce w/dual webers, 1969 1750 Berlina, 1971 1750 Spider Veloce w/ dual webers, 1985 Spider Veloce 23,000 orig. miles, {Two} 1986 Spider Veloces, 1987 Spider Veloce bought new, 1988 Quadrifoglio, 1991 164S, Plus several more. I think they are breeding.
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post #53 of 70 (permalink) Old 12-20-2016, 12:31 PM
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Hi Jim,Good to hear from you.Please don't hesitate to mention anything I've missed,or add what you can.Yes,I do have that information,and I still have some photos of my matching parts to these specs..I was very meticulous when I checked these parts and did the Porsche mods..That's why I doubt messing them up,but not saying that I couldn't have "mixed" the non-moly parts in the process of assembling? We'll open it up and find out,hopefully soon after the holidays.Regards,Phil D
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post #54 of 70 (permalink) Old 01-02-2017, 02:07 AM
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Quote:
Originally Posted by Norseman50 View Post
I am trying to create one serviceable gearbox out of two.

I carefully dis-assembled my '88 and a donor '86.

The 4th gears on both were fine, so I didn't bother to disassemble either input shaft.

But I'm doing the 1st gear fix, and swapping a few dogs and synchro rings, so I measured the output shaft and the existing bronze bushing diameters.

The O.D.'s on the best of the two mainshafts measured:
1st (sleeve): 1.3725"
2nd: 1.3740"
3rd: 1.3754"

The I.D.'s of the best gears (with existing bushes) measured:
1st: 1.3800"
2nd: 1.3795"
3rd: 1.3795"

The resulting clearances, if I choose to re-use these parts without replacing the bronze bushings, would be:

1st: 0.0075"
2nd: 0.0055"
3rd: 0.0041"

Should I replace any (or all) of these bushings?

I'm not sure I've heard a conclusive answer on the allowable clearance tolerances. Since 1st gear sits on a sleeve, I can understand allowing a bit more play there. Is the 0.0080"-0.0120" value (for 1st gear), that was listed above, acceptable?

I'm struggling to offset (a) the cost of new bushings, (b) the difficulty involved in removing and installing the new bushings, (c) the difficulty in finding (and the cost of) a qualified machinist that can center hone the bushings perfectly perpendicular, just to reduce the existing clearances by a few thousandths of an inch. After reading goats' nightmare machinist story I'm wondering if I might be better off with what I have.

Do I really need to get under 2 or 3 thousandths clearance with all of these bushings, or will the diametric clearances of 4 and 5 thousandths on my 2nd and 3rd, or the 7 to 8 thousandths on my 1st gear be okay?

Your knowledge, wisdom and experience are much appreciated.

Found this thread after a search as I'm scratching my head, 'should I replace these bushes?'

What exactly is the tolerance of these bushes? I read that 3thou is the limit, but I cannot find anything referenced back to Alfa Romeo to verify this. I mean in the manual, it doesnt even mention them!

I dont want to be seen to doubt anyone who has far greater experience than the rest of us, but with this sort of thing I always consider there are three possibilities, 1: the absolute ideal wear tolerance (3 thou?), 2: what is acceptable and what most (gearboxes) would measure up and 3: totally wrecked.

I'm quoting Norsman50's post, because out of my proper gearbox and my donor box, all the bush tolerances measure up just about the same as he's reported. So are these 'normal' and 3thou perfect? I'd like to know, because I dont want to go through the agony some have reported here if what I have is perfectly serviceable, but then the agony might be worth it if my bushes fall into the 'wrecked' category. They are:

2nd gear .0062"
1st gear .0055"

Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a 1.6TS 147 in the winter. For special sunny days we have a S2 Spider Junior in the garage.
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post #55 of 70 (permalink) Old 01-02-2017, 02:30 PM Thread Starter
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TopDown you should see in my earlier post the only documentation I have on this. Regardless, my personal opinion is that your clearances are too big. How will this effect gearbox performance? I don't know other than to say it will be 'sloppier' but you won't feel it. What I suspect will happen is that as the clearance gets larger, wear rate will increase, so at some point these gears will be flopping around on the shaft. When? I have no idea! As you can read I shot for .002 +0, -.0005. Got them real close.

Softjaws on a properly set up lathe is the way to go.

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post #56 of 70 (permalink) Old 01-03-2017, 01:14 PM
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Bob, thanks for getting back to me so quickly. Do you mean this reference you made?

"from a technical manual "gearbox" although it says for 1750 model -- but I thought all the 5 speed gearboxes were the same from 1750 to 2000

1st = 0.0049-0.0067
2nd and 3rd - 0.0038-0.0055"

If that is from the Alfa Romeo manual, my bushes are in spec which falls into my #2 category. As far as I can work out, when the gears are spinning on these bushes there is no load on them, when they are driven (under load) they are clamped by the selector ring and will be spinning at the same speed as the sleeve/shaft, isnt that so?

There must be a reason ALfa Romeo gave the measurements they have and not 003thou. After all you need to leave some room for the oil?

I have not made a decision just yet, but I dont want to spend time and money trying to fix something which is in spec.

Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a 1.6TS 147 in the winter. For special sunny days we have a S2 Spider Junior in the garage.
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post #57 of 70 (permalink) Old 01-03-2017, 01:19 PM Thread Starter
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Yes that's the reference. I have it somewhere on paper but don't recall where. The 'do vs don't do' you will have to decide. I have no idea why the ranges were set as they were.

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post #58 of 70 (permalink) Old 01-07-2017, 05:03 AM
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I have now seen an original Alfa Romeo spec sheet from 1989 covering these tolerances. They state:

1st .008 - 0.012
2nd and 3rd .005 - .008

So if its good enough for original build its good enough for me.

Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a 1.6TS 147 in the winter. For special sunny days we have a S2 Spider Junior in the garage.
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post #59 of 70 (permalink) Old 01-23-2017, 05:53 PM
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2nd gear shaft = 1.375
2nd gear bush = 1.377 nice fit, feels good, is it?
according to the parts manual all three tripods have the same part number 101.00.13.218.00

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post #60 of 70 (permalink) Old 01-23-2017, 06:33 PM Thread Starter
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Yep .002 clearance is great as long as it's concentric and perpendicular to gear face. Is the snap ring/dog gear on?
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