AC Lightweight Gearbox

[AEX726]

A question for the masses.  I have an AC engined Aceca that I would like to fit with an overdrive gearbox.  My car came with the Moss box and I have given consideration to obtaining one with overdrive and fitting to my car with the necessary modifications.  An issue I have with this is the problem with worn syncros typical in the Moss box and the inability to replace them.  Being aware that AC offered a "lightweight" gearbox that has been described as TR gears in AC's own casting I am wondering if anyone has attempted to use a TR overdrive gearbox.  The only picture I have seen of one is the cutaway in the owners handbook that looks to me very much like a TR box with the bell housing machined off and a different one bolted on.  Has anyone explored doing this using the AC / Moss bellhousing and a modified TR gearbox (I realize that the input shaft would need to be machined for a female pilot bearing, amongst other modifications).  I am beginning to prefer this option given better parts availability for the Triumph box as well as the remote gear shift position, etc.  I am not interested in any modern 5 speed conversions so I really have these two options.  Your experiences would be appreciated!

[Robin A Woolmer]

Hi
   There are two companies who can fix your Moss Box with new parts to restore the syncro! It is also possable to have the box rebuilt with a completely new set of gears which could offer better ratio's.
   I believe also that close ratio gears may be fitted for performance, i believe this is approx £3,000, but to fit a new first syncro & new bearings & seals is about £600, but you best get a quote from the following.  ' sales@rw-racing.com ' or 'info@jb-engineering.co.uk '
   A company called SC Parts can supply spares ' enquiries@scparts.co.uk '
   
   Robin

[AEX726]

Thank you Robin, have have enquired to both firms.

[Robin A Woolmer]

AEX726
   Would you be good enough to let me know how you get on & what job they do.
   regards
   
   Robin

[Roy Davies]

AEX726.  My 57 Ace has an AC Lightweight Gearbox without an overdrive.  As you probably know, only a handful of these gearboxes (six or seven)were made and have TR internals.  I too intend to fit an overdrive unit and I believe there is an ACE owner out there that has done just that.  That owner should not be too difficult to trace.  You also must bear in mind that the gearbox tunnel is a lot different to that of a Moss box car.

[Robin A Woolmer]

Just Looked on Ebay & you can purchase a Triumph TR gearbox complete with overdrive for less than £500, you might be able to adapt an AC bell housing to fit & i believe the splines on the input shaft are similar to AC. Ypu could purchase an AC bell housing & try it so you do not destroy your existing set up. Not shure how this will go down with purists though!
   
   Robin

[jellison]

TR box should more than handle it - we have two Close ratio one's with special valving for lightning OD changes in our two TR4 and 6 racers.

[AEX726]

Roy - point taken on the tunnel - from the photos I have seen it won't be too difficult to replicate in fiberglass.  If you fit the overdrive to your box please remember that you will need the third motion shaft and the adapter plate as well as the overdrive.  Knowing if the casing is TR with the bellhousing machined off would shed light on whether a TR adapter plate will work on your lightweight box.
   
   Robin - your comments on the cost of a TR box are well taken and another reason I find this option worth investigating when compared with the price of a Moss OD box.  I really think the key is whether an AC bellhousing would work on a machined TR box.  The splines are not going to be a problem but you will need to machine the input shaft and fit a pilot bushing in it as the AC has the bushing in the input shaft as opposed to the TR where it is in the end of the crankshaft.  The big question in my mind is the depth of the AC bellhousing relative to the length of the input shaft of the TR box.  I may do some investigating at the local shop I used to work at who has both TR and Moss boxes that are out of their respective cars.  (Can't check on mine since the car is together).  I'll keep you posted.  Not too worried about the purists since this is pretty much to what AC offered (ie not a 5 speed conversion or somthing of that kind).

[Kiwi 2Litre]

Hi, How have you got on with your gearbox and O/D? I work for a company which does modern five speed conversions but it would not be difficult to cast a bellhousing to adapt the Triumph box to the AC engine. I have a block and bellhousing and the company has Triumph casings and bits for developement purposes. I thought I had read somewhere that AC had made their own gearbox casing to suit the Triumph gears but that would be a lot more work. Have a look at www.conversioncomp.com if you want to contact us. Cheers, Ian.

[1744]

quote:Originally posted by AEX726
   
A question for the masses.  I have an AC engined Aceca that I would like to fit with an overdrive gearbox.  My car came with the Moss box and I have given consideration to obtaining one with overdrive and fitting to my car with the necessary modifications.  An issue I have with this is the problem with worn syncros typical in the Moss box and the inability to replace them.  Being aware that AC offered a "lightweight" gearbox that has been described as TR gears in AC's own casting I am wondering if anyone has attempted to use a TR overdrive gearbox.  The only picture I have seen of one is the cutaway in the owners handbook that looks to me very much like a TR box with the bell housing machined off and a different one bolted on.  Has anyone explored doing this using the AC / Moss bellhousing and a modified TR gearbox (I realize that the input shaft would need to be machined for a female pilot bearing, amongst other modifications).  I am beginning to prefer this option given better parts availability for the Triumph box as well as the remote gear shift position, etc.  I am not interested in any modern 5 speed conversions so I really have these two options.  Your experiences would be appreciated!
   

[1744]

quote:Originally posted by Robin A Woolmer
   
Hi
   There are two companies who can fix your Moss Box with new parts to restore the syncro! It is also possable to have the box rebuilt with a completely new set of gears which could offer better ratio's.
   I believe also that close ratio gears may be fitted for performance, i believe this is approx £3,000, but to fit a new first syncro & new bearings & seals is about £600, but you best get a quote from the following.  ' sales@rw-racing.com ' or 'info@jb-engineering.co.uk '
   A company called SC Parts can supply spares ' enquiries@scparts.co.uk '
   
   Robin
   

[1744]

I converted (1993) my light weight gearbox to accept the Laycock A Type OD.It was a bolt on situation but did require a TR 6 Main shaft shaft (short) modified by boring front of shaft per original AC shaft.All other internals in the light weight box remained as originally supplied by AC,ie TR 3.The bell housing rear mount and rear mount remained again,as supplied by AC
   
   Jonathan Parker
   
   AEX 1194

[Robin A Woolmer]

It is interesting that the AC Engine crank has the unusual feature of supporting the gearbox driven shaft needing the driven shaft to be bored to take a bronze bush, this makes conversions more difficult.The reason for this is due to the crank being in two parts.
   My new crank design is adopting the more convensional approach as most replacements cranks are from solid billet, so it is possable to fit a bush in the crank boss or the flywheel (if renewed). This has the option of continuing with the AC approach by fitting a dummy shaft or fitting a different gearbox of a later variety.Therefore a greater gearbox choice may be made, but it does depend on economic grounds, but if a new crank is being considered it's worth some consideration.
   
   Regards
   Robin

[Roy Davies]

Jonathan Parker.  Could we have a chat about how you fitted an OD unit to your Lightweight gearbox.  I would like to do the same.  Thanks.  Roy

[1744]

quote:Originally posted by Roy Davies
   
Jonathan Parker.  Could we have a chat about how you fitted an OD unit to your Lightweight gearbox.  I would like to do the same.  Thanks.  Roy