SpringDon

Well-Known Member

• Mar 11, 2012

• #1

Rebuilding the a series 3 gearbox and replaced first gear (genuine part used).
On reassembly the gearbox would lock up whenever a gear was selected.

I found this was caused by the rear syncro cone jamming on first gear so it was like first was permanently selected. If I push the cone onto the gear with my thumb (gear off the mains half) it needs to be levered off.
I'm loath to reassemble the box in this state. Is it normal for a new gear and cone to be sticky on the bench and would you expect it to be fine when the engine's running and the shaft spinning?

Been ****ing about with it for days now and wonder whether I 'd be better off putting the old gear back in as the cone is a loose fit on that.

 

jamesmartin

Well-Known Member

• Mar 11, 2012

• #2

to check them you hold both and screw/'twist baulk ring on to cone, if it is rocky or jams buy another baulk ring when held on there needs to be 25 thou gap between baulkring and gear dog teeth check with feeler guage,i build them regular so if your worried about something just ask dont forget 3rd/4th synchro unit has recess in splines on inner they go over snap ring holding 3rd gear

 

SpringDon

Well-Known Member

• Mar 11, 2012

• #3

I've tried 2 (bearmach) rings both of which jam on the new gear but not on the old gear. I'll measure the gap tomorrow.

Everything else eems fine so I'm thinking the gear is no good.
Thanks

 

Last edited: Mar 11, 2012

jamesmartin

Well-Known Member

• Mar 11, 2012

• #4

new gears arent as well made as all new parts for them,i struggle sometimes with parts,try it lightly oiled

 

SpringDon

Well-Known Member

• Mar 12, 2012

• #5

Measured the gap at 50 thou on the old gear and about the same on the new gear.
After pressing in the main shaft, I can free off the cone using hooks and mirror then it all shifts and turns ok.
If I do that and reassemble to box, is it just a matter of time before it sticks or would that not happen with a running engine( and I assume more torque twisting the gear and cone apart than I can manage on the bench)

 

jamesmartin

Well-Known Member

• Mar 12, 2012

• #6

its hard for me to say as i cant feel from here ,one way would be to loosely assemble main shaft and try engaging gears fully by pulling synchro hub sleeve over and then back to neutral 50 thou is too much it make me think baulk ring wasnt good

 

SpringDon

Well-Known Member

• Mar 12, 2012

• #7

I can select first on the loosely assembled main shaft as long as the cone doesn't stick. The old gear is less prone to sticking but is slightly worn, but I guess better a worn gear than a stuck cone.

These cones are the second set I bought as the first Britpart pair looked so bad that I didn't even bother trying to fit them.

 

jamesmartin

Well-Known Member

• Mar 12, 2012

• #8

SpringDon said:

I can select first on the loosely assembled main shaft as long as the cone doesn't stick. The old gear is less prone to sticking but is slightly worn, but I guess better a worn gear than a stuck cone.

These cones are the second set I bought as the first Britpart pair looked so bad that I didn't even bother trying to fit them.

Click to expand...

id have tried to fit them ive used them before,old gear slightly worn on dog teeth front edge or pitting on gear teeth,either gear is poor or baulk rings ,allmakes usually arent bad with that kind of part

 

SpringDon

Well-Known Member

• Mar 14, 2012

• #9

I spoke to a very nice man at R.Whitehouse & Sons (gearbox rebuilders) who said that 50 thou was at the top end of acceptability. He also said that if you look down the side of the 3 lugs that engage the syncro hub, the dog teeth should line up with the side, I.e. You shouldn't see part of the tooth.

The bear mach rings were ok, the cheapest Britpart ones were not. He also said the hardest part of the job was finding good parts as most new ones were crap.

Just going to put it back together now and hope for the best. Thanks for your advice again.

 

jamesmartin

Well-Known Member

• Mar 14, 2012

• #10

it is true parts are often poor even genuine which is unlikely for series isnt going to be made here, poland or worse,you have to make decsions which is hard if some one wants a guarenteed perfect box first time as things are now ,often they are fine or run in ,