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Gearbox guru please #683286
02/01/17 7:52 am
02/01/17 7:52 am
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Last edited by NickL; 12/02/17 10:19 pm.


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Re: Gearbox guru please [Re: NickL] #683318
02/01/17 12:14 pm
02/01/17 12:14 pm
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DMadigan Online content
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Not a "guru" but familiar with the alternate gears in the A65. Since the shaft centre distant is constant a one tooth change requires cutting a special addendum since a nominal pitch diameter would require a different shaft spacing. So using a 23 tooth mainshaft with the matching layshaft gear for the 24 tooth would result in a lot of backlash. The other way around, the 24 tooth mainshaft with the matching layshaft gear for the 23 tooth mainshaft would bind.

Re: Gearbox guru please [Re: NickL] #683320
02/01/17 12:41 pm
02/01/17 12:41 pm
Joined: Apr 2014
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Quebec Canada
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Hermit Online content
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Hi NickL -
I am definitely not a guru, gearbox or otherwise, but during the two years it took me to work through a similar problem on my '69 T120R I collected some resources - including a couple of Triumph bulletins about '69 models jumping out of gear.

You can have a look at these resources here:

http://www.hermit.cc/tmc/om/manual.htm#gearbox

(See links to "Triumph Bulletin #8-59" and "Troubleshooting Bulletin Gearbox Excerpt" in the section "Jumping out of Gear").

My gearcluster had (has) a third gear that doesn't match what #7 said it should be, but that turned out to not be a problem.

The solution to my bike's jumping out of gear was to replace the
57-0408 Gearshift quadrant (Ref# 8 Fig. 9 Page 29 #7).

Actually, as it turned out I could have ground a bit OFF the downshifting "stop" on the quadrant and everything would have been fine. Why that became necessary after so many years and miles (66,000) I don't know, but letting the outside quadrant travel a little more when downshifting turned my cranky gearbox into a very nice, smooth unit. Note that Triumph Bulletin #8-59 suggests ADDING material to the other stop when the gearbox jumps out of 3rd when UPshifting.

For me the takeaway is that those two stops are critical to correctly operating the INNER quadrant (57-0397, Ref# 17 Fig.7 Page 25 #7) and therefore the camplate and fork shifters.

So, does your bike's gearbox jump out of 3rd after UP shifting, or DOWN shifting? Especially if it's one or the other, take a close look at the appropriate stop on that outside quadrant and you might find the problem.

Good luck! And be sure to let us know what fixed the problem when you succeed.


Bruce Miller
aka The Hermit
www.hermit.cc/tmc
Re: Gearbox guru please [Re: NickL] #683431
02/02/17 1:12 pm
02/02/17 1:12 pm
Joined: Apr 2014
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Quebec Canada
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Here's a link to some photos of gears in my '69 T120R. - maybe you can compare with your stuff.
www.hermit.cc/tmc/bb/2015/wtd_2/index.htm

There are also pics comparing new and original parts, including camplates. I fretted over camplate 'differences', but like your shop said, probably not a problem.

Originally Posted By NickL
When 3rd gear is selected the engagement of the 3rd gear is well short of 'home' and it's no wonder the damn thing is jumping out of gear. The dogs are at

least 2mm out.


It sounds like you may have located the problem, but it couldn't hurt to step back for a moment and answer one question. Ok, two questions.

1) Did the bike always jump out of 3rd as long as you've had it?

2) No matter whether it's right away or some time after you've shifted gears, does the gearbox pop out of gear only after you have shifted either up or down? Or does it pop

out of gear going both ways?

If the problem occurs exclusively after shifting up or shifting down, would that point to gears or dogs being the problem, or would it more likely indicate malfunction of a part

or 'part of a part' that works bi-directionally?

Ok, I'll quit, I'm up to four.


Bruce Miller
aka The Hermit
www.hermit.cc/tmc
Re: Gearbox guru please [Re: NickL] #683598
02/03/17 7:45 pm
02/03/17 7:45 pm
Joined: May 2009
Posts: 613
San Rafael, Ca.
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I'm not a gearbox guru by any stretch of the imagination but the T916/T1065 2nd gear combination and T926 1st gear layshaft were used until early 1969, suggesting you have an early 1969 gearbox. The 57-3889/57-3890 combination you've ordered is a late 1969-70 gear set. Triumph increased the layshaft spline size in late 1969. The 57-3890 layshaft 3rd gear may not be compatible with your layshaft.

Eric


1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Gearbox guru please [Re: NickL] #683627
02/04/17 12:14 am
02/04/17 12:14 am
Joined: May 2009
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San Rafael, Ca.
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Yes, Triumph changed the gear surface finish in early 1969, necessitating a new batch of part #s. Then they changed the spline diameter a few months later and at the beginning of the model year they changed the 3rd gear ratio. That's 4 different gear sets in a few months. If you're lucky, whoever installed the 57-3858 mainshaft 3rd gear installed its 57-3860 layshaft mate and the big spline layshaft.

Eric



1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Gearbox guru please [Re: NickL] #683648
02/04/17 8:05 am
02/04/17 8:05 am
Joined: Mar 2006
Posts: 3,488
Norfolk, UK
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Originally Posted By NickL
(minutes from triumph boardroom meeting)


Minutes from the BSA Group boardroom more like.

Triumph was part of the BSA Group and therefore not completely in control of its own destiny at that time. Decisions, including the reason for various dimensional changes made to the '69 gearbox components, were often made at a higher level (see 'Bonnie' by J R Nelson).

Re: Gearbox guru please [Re: NickL] #683751
02/05/17 3:04 am
02/05/17 3:04 am
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Oh, those (B)loody (S)illy (A)uthoritarians !! Not you, Nick, the management drongos !

Last edited by Triless; 02/05/17 3:09 am. Reason: clarification
Re: Gearbox guru please [Re: NickL] #683760
02/05/17 4:59 am
02/05/17 4:59 am
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Nick, most of my Triumph gearbox work has mostly been with T140 five speeders. Having said that, though, I have had a little experience with unit 500's ( disassembly, check, reassemble, but no problems) and with 650's, mainly'66 and ' 69 ( the same ).
These gearboxes were in good condition, so everything was OK. Plus I was lucky, I guess. There was no need for shimming, selection was fine, and this was a few years back, so maybe not as worn. I have not worked on a 1970 leaf spring indexed gearbox.
In 1969, at engine number CC 15546,the dimensional changes to the gearbox shaft running diameters and gear bore diameters were introduced. These are not to be mixed with previous.
I remember reading somewhere that previously, gearbox manufacture was done "the Meridan Way (!)". Then they decided to produce the components to the drawings !!!!!!!??

Re: Gearbox guru please [Re: Triless] #683773
02/05/17 8:17 am
02/05/17 8:17 am
Joined: Jun 2002
Posts: 9,536
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Hi,

Originally Posted By Triless
Then they decided to produce the components to the drawings

I believe it was as a result of the MIL-TFD-1111 requirement.

Regards,

Re: Gearbox guru please [Re: Stuart] #683779
02/05/17 9:07 am
02/05/17 9:07 am
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Ah, so thats what they called it !
According to John Nelson in "Bonnie", the " powers that be" decided that the gears and shafts were common to the triples, the gearbox components would be manufactured at Small Heath. This resulted in parts dimensions being altered after about thirty years !
Meriden should have amended the drawings years previously to put them in line with the many years of proven and accepted practice,but it was decided that the parts manufactured at Small Heath must be finished to the original drawings !
Unbelievable, really !( Actually, I hope Nick doesn't tell those one eyed BSA twin and Norton twin blokes any of this !)

Last edited by Triless; 02/05/17 9:14 am.
Re: Gearbox guru please [Re: NickL] #683792
02/05/17 11:17 am
02/05/17 11:17 am
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BSA at this point was starting to hemorage Pounds. The gears were just one of the efforts to homolagate production between the brands. It made little sense to have production of what would be the same part at two separate facilities that had the clearances derived from two different engineering practices.

With engine production of the triple done at Small Heath it made little sense to split production of what was the same gear set. Another example of this, and the confusion it would eventually cause, was the changes made to the rocker arms that were also made at Small Heath.

BSA didn't run over a financial cliff in 1972! It was more like tumbling down a gentle grade that started years earlier. All of these efforts were akin to "putting a finger in the dike". All blame doesn't rest on the shoulders of BSA management. US management in the name of the late Peter Thornton's two year attack on the AMA's national number one racing plate went a long way to finish BSA off. No "stone was left unturned" and no dollar left unspent.
John


Re: Gearbox guru please [Re: NickL] #683850
02/05/17 8:10 pm
02/05/17 8:10 pm
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desco Online content
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NickL,
No need to be horses a**. I lot of people do like to hear the history of these old turds. I am one of them. Especially when it explains some of the mystery and mystic of otherwise senseless changes.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: Gearbox guru please [Re: NickL] #683864
02/05/17 10:08 pm
02/05/17 10:08 pm
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Nick, my four speed experience was in conjunction with engine builds for other people, and as I said, the boxes were in generally good condition. I would say clearances were generous, and in line with advice I had recieved, I checked for the usual things, such as bluing on selector forks and tracks in gears, worn selector plate slots, and fork guide pin rollers ( the last two would cause lost movement),and, obviously, worn and rounded dogs .Much in line with what Bruce has previously said.
Wear in the third gear dogs wouldn't be helped with generous clearances and the attrition of age.
Simply put, I never have needed to shim. But an instance I heard about a hard ridden 650 with the problem you are experiencing was due to worn dogs, but being a couple of years earlier than yours , replacement wasn't a drama ! And as far as I know, that fixed the problem.

Re: Gearbox guru please [Re: NickL] #683939
02/06/17 1:31 pm
02/06/17 1:31 pm
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OK after typing all this in the post disappeared for no apparent reason after a half hour of typing. I will give it one more go as I am ignoring customers to do this.
I promised my self that I would not get caught up in this as the answer is not straight forward.

Transmissions of this era have several conditions:

Shaved and non-shaved gears.
Stepped and non-stepped shafts.
Gears in two conditions to fit the stepped and non-stepped shafts.

The non-stepped lay shaft has a major shaft diameter of 1.123" to 1.1225".
The stepped lay shaft has a major diameter of 1.123" to 1.1225" and a minor shaft diameter of 1.1190" to 1.1185"

The non stepped main shaft has a major diameter of 0.9985" to 0.9980".
The stepped main shaft has a major diameter of 0.9985" to 0.9980" and a minor shaft diameter of 0.9945" to 0.9940"

Non-splined gears bore diameter are the same for both conditions.
Splined gear's bores vary to be compatible with their respective stepped or non-stepped shafts.

The T916 main shaft 2nd small bore (stepped shaft) used up to early 1969.
The 57-3858 is an alternative for T917 replaced by the 57-3858 up to early 1969. It was used with 57-3860 (22T) lay shaft 3rd for the stepped shaft.
The 57-3858 (24t) can be replaced with 57-3889 (23T) main shaft 3rd + 57-4155 non-stepped lay shaft + 57-3890 lay shaft 3rd (22t). These three must be used as a set when replacing the 57-3858.

It is obvious that you cannot fit a splined gear for a stepped shaft on a non-stepped shaft. Less obvious is fitting a splined gear for a non-stepped shaft on a stepped shaft. This is going to cause all sorts of shifting problems.

The gears you listed are all for a non-stepped condition (up to early 1969) so fitting non-stepped gears could cause you problems.

Classic black socks is my guess...


Last edited by John Healy; 02/06/17 1:48 pm.

Re: Gearbox guru please [Re: John Healy] #683967
02/06/17 5:00 pm
02/06/17 5:00 pm
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Triless Online content
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Thanks for this, JH. Its going into my permanent files for sure.

Re: Gearbox guru please [Re: NickL] #683982
02/06/17 8:07 pm
02/06/17 8:07 pm
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Nick, I don't think its the fault of the gearbox as such in this case, but more lack of communication between two group factories at that time.
The thing that most annoyed me with the unit four speeds was the " first gear crunch ".
I believe the first time the unit five hundreds were raced in America there were problems with gearboxes, but mostly the 650 gearboxes were OK. Maybe didn't shift as sweet as the AMC.

Re: Gearbox guru please [Re: NickL] #683986
02/06/17 8:20 pm
02/06/17 8:20 pm
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San Rafael, Ca.
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Originally Posted By NickL

So it appears i've just wasted a load of money on gears i can't use (unless i buy a layshaft as well) 57-4155. Is the old heap worth it, i ask myself? OR, as i've achieved good results with the shimming etc i've done do i just box it back up again, another layshaft means top gear with it i suppose so another 3-400 dollars on top of the 400+ so far. These Triumphs are an expensive toy.


Not necessarily. As John says:

Originally Posted By John Healy

The 57-3858 is an alternative for T917 replaced by the 57-3858 up to early 1969. It was used with 57-3860 (22T) lay shaft 3rd for the stepped shaft.


The 57-3860 layshaft 3rd is for a non stepped layshaft. There's a chance whoever installed the 57-3858 mainshaft 3rd upgraded to the 57-3860 layshaft 3rd and a non steeped layshaft. If that's the case, the gears you ordered should fit.




1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Gearbox guru please [Re: NickL] #685046
02/16/17 3:31 am
02/16/17 3:31 am
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Triless Online content
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Good on you, Nick. Your actions re shimming are duly noted.
I'll give you the drum, for a transported pom, you're not a bad sort of drongo !
Now, about your book ..............


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