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Rating: 4
Pre-Unit Transmission Info, Swing Arm Models
#713333 10/31/17 12:06 pm
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Rich B Offline OP
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This is not my work, I believe it was the work of Dave Kath some years ago. GStar Ron may have contributed as well. I keep a copy of this in my book with all of my pre-unit printed information. Lots of good information here. I will make it a sticky thread since questions about pre-unit gearboxes come up from time to time. grin

Through the magic of cut & paste, here are the wise words from a number of years ago:

"I frequently come across problems of the incorrect assembly of the layshaft thrust washers in the swing arm type gearbox, of the type with the needle roller layshaft.

There are four large hardened washers used in the gearbox, three on the layshaft and one behind the ratchet pinion bush and it's possible to assemble the gearbox with some of these four in the wrong position. Unfortunately the BSA spares list illustration does not show clearly the correct assembly.

Working from the clutch end of the gearbox, the washers should be assembled on the layshaft in the following positions.

42-3078 ... 1.156" OD, 0.687" ID, o.108" thick
fits between main shell and layshaft 'B' gear.

67-3203 ... 1.094" OD, 0.750" ID, 0.093" thick
fits between the 'F'
layshaft 3rd and 'H' 1st gears.

42-3079 ... 1.250" OD, 0.750" ID, 0.113" thick
fitted between the 'H' layshaft 1st and the middle 'sandwich' case.

67-3161 ... 1.162" OD, 0.750" ID, 0.075" or 0.068" thick
fitted behind the kickstart ratchet pinion bushing.

Pay particular attention to the washer p/n 67-3203, which is also used on the gearboxes fitted with bronze layshaft bushes. The bore of the washer often only has a chamfer on one side only. If this is the case, the washer must go onto the layshaft with the chamfer against the spline to give clearance for the small radius on the shaft at the start of the spline.

Be very very careful of the improperly sold repop 'T' layshafts. There are a couple of subtle dimensional differences between the STD bushing layshafts and the STD T needle roller shafts but some suppliers want to sell a 'one part fits all'.

'Bushing' Box info
The 42-3019 'bushing' lay shaft has oil grooves on the end adjacent to the clutch.
bearing surface diameters:
clutch end ... ~ 0683"
speedo drive end ... 0.7475"

'B' gear, aka 'layshaft 4th' tooth width is 0.660"

'A' gear, aka mainshaft sleeve gear, tooth width is 0.560"
note: both are narrower than the 'T' box gears.

'T' Box info
The 42-3094 Timken needle bearing lay shaft used in 'T' Gold Star boxes is almost identical to the shaft in a bushing box, but there is Never a oil groove in the bearing ends. The bearing ends are also 2.5 thou larger than the bushing shaft. Measure.
bearing surface diameters:
clutch end ... 0.686"
speedo drive end ... 0.750"

'B' gear, aka 'lay shaft 4th gear' is 0.740" wide across the teeth.
'A' gear, aka 'mainshaft sleeve gear, is 0.603" across the teeth.
note both gears are wider than the 'bushing' box gears.

'T' box thrust washer info:
42-3078 - Fitted between main shell and the layshaft fixed 'B' gear.
1.156" OD, 0'687" ID, 0.108" thick

67-3203 - Fitted between the layshaft 3rd 'F' and layshaft 1st 'H' gears.
1.094" OD, 0.750" ID, 0.093" thick

42-3079 - Fitted between the layshaft 1st 'H' gear and the middle case.
1.250" OD, 0.750" ID, 0.113" thick

67-3161 - Fitted behind the kickstart ratchet pinion bushing.
1.1625" OD, 0.750" ID, 0.075" (or 0.068") thick

Note:
67-3203 is also used in bushing boxes. If this washer has only one chamfer on the ID, fit the chamfer against the layshaft splines to give clearance for the radius.

Mainshaft Info
There were 4 different mainshafts used in these gearboxes.
RRT2 shaft 42-3131 for use with needle bearings in the 'A' sleeve gear

STD(T),RR(T),DAY(T) 67-330 shaft used in both the bushing and 'T' boxes

SC(T) shaft 67-3315 is slightly different than the STD shaft. This shaft can be used in a STD box, but not visa versa.

TRI(T), STB(T) shaft 67-3313 identical to the SC shaft except the 'G' 1st gear is made as part of the shaft vs pressed on.

There are 17 gear sets listed to make up the 7 different ratio transmissions both with and without the Timken bearings. Some gears are used in multiple applications, but some are unique to a particular box. And you can create your own ratios with a bit of 'mix and match' of the gear sets."

Last edited by Rich B; 10/31/17 12:08 pm.

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Re: Pre-Unit Transmission Info, Swing Arm Models
Rich B #713684 11/03/17 2:53 am
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For anyone getting ready to rebuild a complete T-type gearbox (STDT, SCT, etc.), it will cost a minimum of ~$25 if everything inside is in good shape. Which, of course, it won't be. If the gears are in reasonable condition but all the bearings and bushes need replacing the rebuild cost could be as much as $250. Although a few parts are different, the cost to rebuild a bushing gearbox or an RRT2/SCT2 will be about the same.

Before you open your gearbox you might arrange to have the first set of items below on hand because even if you find nothing broken or worn inside you will need these to put it back together. You also should have $150 in your bank account and a further $100 line of credit in order to be ready for the worst case eventuality. The numbers come from Plate 3 (Gearbox) of the DBD parts manual.

Every rebuild definitely will require:

No.__Part No.__ Description
2____67-3067__ Gearbox sprocket oil seal
46___67-3346__Gearbox inner cover joint washer
53___24-8504__Gearbox casing plug washer
59___29-3449__Gearbox inspection cover washer
105__67-3354__Gearbox outer cover joint washer
116__64-3106__Inspection cover joint washer
Yamabond 4 or your favorite equivalent gasket sealant
approx. total $25

Your rebuild also may or may not need some or all of the following bearings:

3___24-4065__Constant mesh gear ball bearing
14__24-4217__Mainshaft bearing
72__42-3074__Layshaft needle roller bearing
75__42-3075__Layshaft needle roller bearing (cover end)
approx. total $75

Repeating some of the information from a different thread, a caged needle bearing will have only ~20% the lifetime of a full complement uncaged bearing of the same quality so it is well worthwhile to use the latter.

You also may need some or all of the bushes:

4____67-3073__Constant mesh gear bush
6____67-3080__Constant mesh gear bush (drilled)
17___67-3169__Kickstart ratchet pinion bush
101__67-3093__Layshaft gear bush
approx. total $80

You only will need the following if they missing from your gearbox or excessively worn:

16___67-3161__Kickstarter ratchet pinion sleeve washer
73___42-3078__Layshaft thrust washer (clutch end)
74___42-3079__Layshaft thrust washer (cover end)
99___ 67-3203 (replaced by 57-1962)__Layshaft thrust washer
approx. $70

Re: Pre-Unit Transmission Info, Swing Arm Models
Rich B #759311 12/14/18 8:13 pm
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I am not sure who maintains this thread but, I thought the information in the attachments may be helpful in identifying transmission codes.[img]http://[/img]

Attached Files BSA Bulletin 93 1.jpgBSA Bulletin 93 2.jpg

1951 ZB GS
1953 BB GS
1953 Super Flash
1954 Vincent BS
1963 RGS
1956 Triumph T110

Re: Pre-Unit Transmission Info, Swing Arm Models
Rich B #777058 06/22/19 8:37 pm
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WOW! Lots of good information. I suppose I should add some to the information about this particular B31. The guy who had it built (I can't remember his name) was the guy who ran a business called Brit Tech. He did things with British cars. He had this built four of five years ago. It is a Gold Star replica. There has been some magic applied to the bottom end. It has a 500cc barrel, and a DBD34 head and cams. It has an AMAL Mk II carb. The bike runs very well. After reading a bit about these transmissions, the problem might be a broken detent spring, but don't assume I know anything.


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Re: Pre-Unit Transmission Info, Swing Arm Models
Rich B #810256 05/25/20 6:03 pm
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I need an I.D. on the following:
1st gear - layshaft "H"
26T

I came across this while sorting my gear inventory. No 26 tooth shows up on the BSA gearbox chart or any parts catalogs(1952 to 1960). The G/B chart shows only 24T, 25T, 27T and 29T.
Whatever it is, I've got six of them.

[img]http://[/img]

Attached Files 100_6576.JPG

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Re: Pre-Unit Transmission Info, Swing Arm Models
BritTwit #810261 05/25/20 6:30 pm
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Originally Posted by BritTwit
1st gear - layshaft "H"
26T
Hmm, although in at least one case BSA got away with a 1T difference from maintaining a constant sum, all the listed H and G pairs sum to 43T. This means that normally your 26T gear H would require a 17T mating gear G. However, the listed ones are 14T, 16T, and 18T, so your 26T gears represent a double puzzle.

Re: Pre-Unit Transmission Info, Swing Arm Models
BritTwit #810332 05/26/20 8:13 am
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Originally Posted by BritTwit
I need an I.D. on the following:
1st gear - layshaft "H"
26T

I came across this while sorting my gear inventory. No 26 tooth shows up on the BSA gearbox chart or any parts catalogs(1952 to 1960). The G/B chart shows only 24T, 25T, 27T and 29T.
Whatever it is, I've got six of them.

[img]http://[/img]
Missed it by that much.

According to MCE 575-2 (1949 - '53 parts book), 65-3441 is "Layshaft gear (26T) with bush" for the rigid/plunger Gold Star Clubmans
It mates with 65-3436 "Mainsheet gear (23T and 19T)"
The other layshaft gear for that set is 66-3266 "Layshaft gear (22T with bush)"

It appears that the earlier gearbox pinion pairs added up to 45T instead of the later 43.

The BSA CD set is handy for wasting lots of time.

Re: Pre-Unit Transmission Info, Swing Arm Models
Shane in Oz #811672 06/06/20 3:53 pm
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Shane
A belated thank you for looking into this. Unfortunately, we still have a mystery. I had a plunger gear cluster on the shelf and the 26T lay shaft gear (65-3441) has entirely different engagement dogs. The 65-3441 has nine raised dogs. The mystery gear has six drilled slots (see above).

The only other explanation I have, is the source of these gears. They came from a large BSA inventory from a BSA tuner in SoCal. There were a lot of other strange gears as well as a set of NOS Magnesium gear box shells. There were other gears that had hard to read tags with notes on Daytona ratio combinations. So, this may allude to special gears from the BSA race shop or something made up on the west coast.
The final question, what the hell am I going to do with six of these?


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Re: Pre-Unit Transmission Info, Swing Arm Models
BritTwit #811696 06/06/20 7:43 pm
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Dan, I also found one in my gear junk pile. It is for a plunger frame Goldie 49-52, extra close ratio part number 65-3441, 26 teeth gear 'F' on the chart. Wow, you are sitting on a gold mine! Lloyd

Main shaft- 'A' gear 26 teeth, 'B' gear 25 teeth, 'C' gear 19x23 teeth
Lay shaft- 'D' gear 19x20, 'E' gear 22 teeth, 'F' gear 26 teeth

Last edited by bsalloyd; 06/06/20 7:56 pm. Reason: added information

1951 ZB GS
1953 BB GS
1953 Super Flash
1954 Vincent BS
1963 RGS
1956 Triumph T110

Re: Pre-Unit Transmission Info, Swing Arm Models
bsalloyd #811701 06/06/20 8:24 pm
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[img]http://[/img][img]http:
this is the 65-3441

//www.britbike.com/forums/ubbthreads.php/ubb/download/Number/8709/filename/100_6576.JPG[/img]

Attached Files 65-3441.jpg

Coming to terms with your delusions, is the first step to sanity
Re: Pre-Unit Transmission Info, Swing Arm Models
BritTwit #811710 06/06/20 9:34 pm
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Okay, back to the drawing board!


1951 ZB GS
1953 BB GS
1953 Super Flash
1954 Vincent BS
1963 RGS
1956 Triumph T110

Re: Pre-Unit Transmission Info, Swing Arm Models
Rich B #811717 06/06/20 10:53 pm
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Hi
Is it from an A65?
A65 1st gear pairs have been used to lower 1st gear on RRT2 gearboxes
I have an A65 pair somewhere ?

John

Re: Pre-Unit Transmission Info, Swing Arm Models
Rich B #811732 06/07/20 4:20 am
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and speaking of BSA trannies... Some years ago I bought a Triumph 4 speed box with the plan to fit a 5 speed Triumph gear cluster for one of my Goldies. BTW, my friend Ken Lighthouse built one of these for his Goldie racer with good success. Not having any luck finding the Triumph 5 speed pieces, I took an easier route and purchased a Nova 5 speed gear set.
Anyhow I would like to send the complete Tri 4 speed to a 'good home' at a reasonable price. The box is disassembled and all of the pieces look okay. Offers?


Dave - NV
Re: Pre-Unit Transmission Info, Swing Arm Models
chaterlea25 #811803 06/08/20 1:00 am
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Originally Posted by chaterlea25
Hi
Is it from an A65?
A65 1st gear pairs have been used to lower 1st gear on RRT2 gearboxes
I have an A65 pair somewhere ?

John
I think John may be the winner. My 1967 A65 parts manual shows a 26 tooth lay shaft gear part number 68-3151.


1951 ZB GS
1953 BB GS
1953 Super Flash
1954 Vincent BS
1963 RGS
1956 Triumph T110


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