21 replies to this topic

[pistin broke]

hi
been offered a 3 synchro box sc its had a full recon he wants about
£200 for it . im building a 1330 .is it worth having .its an a series early remote with
no drop gears.And whats the differance between 3 and 4 synchro ..thanks

[Grayedout]

Basic difference is a 3 synchro has no synchromesh on 1st gear. What this means for driving is you will not be able to select 1st gear until the car is absolutely stationary!

No reversing from your drive, dipping the clutch and selecting 1st while still moving backwards etc !

[Guess-Works.com]

Also the improvements which were built into the A+ design will not be there...

There was a 3 synchro ST SC gearset which went on ebay for 70 quid just a few days ago...

They are realy a specialist item, and although I would say not bad, compared to a later A+ box fitted with 4 synchro SC gears and uprated shafts, is no comparison.

[m1n1]

why you would have to stop to select first gear? The double de-clutch method should be used.

[icklemini]

Have done a few 3sync boxes but these have been for restoration jobbies..

unless you have a specific need for it to be 3-sync, then IMHO i wouldnt bother with it and go for a later style box. Spares are getting hard for these now. laygear and 1st gear get a hammering due to no synchromesh.. 1st motion bearing is different and NLA too. (though i do have a stash!)

TTFN,
Dave

[mini1071s]

Also the improvements which were built into the A+ design will not be there...

There was a 3 synchro ST SC gearset which went on ebay for 70 quid just a few days ago...

They are realy a specialist item, and although I would say not bad, compared to a later A+ box fitted with 4 synchro SC gears and uprated shafts, is no comparison.

Ooops, er, the A box was made out of better materials. The A+ box was made out of lesser materials and the engineers upgraded the sizes of parts to compensate. There are no real differences in the resulting strength.

You don't need to stop, as icklemini said, just double declutch. Easy when you know how to.

A 3 synchro box is a PITA though.

[Guess-Works.com]

Also the improvements which were built into the A+ design will not be there...

There was a 3 synchro ST SC gearset which went on ebay for 70 quid just a few days ago...

They are realy a specialist item, and although I would say not bad, compared to a later A+ box fitted with 4 synchro SC gears and uprated shafts, is no comparison.

Ooops, er, the A box was made out of better materials. The A+ box was made out of lesser materials and the engineers upgraded the sizes of parts to compensate. There are no real differences in the resulting strength.

You don't need to stop, as icklemini said, just double declutch. Easy when you know how to.

A 3 synchro box is a PITA though.

I disagree, the main benefit of the later A+ box is the removal of one of the holes in the third motion bearing retaining web, also the larger 3rd motion shaft, and the improved Idler bearing size..

I use to run A series boxes on my 1330, and was getting fed up rebuilding them because of that weakness.. I now use late A+ boxes for all higher performance gearbox requirements.

[Dan]

Also remember that early 3 syncro boxes have two different casing sizes, one for small bore engines and one for large bore. You can't fit any 3 syncro box to any engine as you can with 4 syncro boxes. If the box you were offered was built for an 850 it won't fit your 1330.

Can we please sort out what terminology we use for gearboxes. I've said before that we shouldn't refer to them as A+ or not as there's a lot more change points for gearboxes than for engines. Above Mini1071S talks about A boxes, I think of an A box as being the very first 3 syncro box with the type A gear set. The rubbish one! Maybe it's just me that thinks differently to everyone else on this.

Edited by Dan, 08 February 2006 - 12:46 PM.

[icklemini]

You don't need to stop, as icklemini said

No i didnt!!

[dklawson]

As one of the guys driving a 3-synchro box....

You'd be a fool to select first by double de-clutching. Yes... it can be done. BUT it puts unnecessary wear and tear on components (that as were mentioned above) are NLA. Coming to a complete stop for first isn't as awkward as you think. Midget, Minor, MGB, and early Mini drivers have been doing it for years. by the way, when you have a 3-synchro box it's also customary at a stop to push in the clutch, then pull the gear lever back into second BEFORE moving it forward into first. Failing to do this you'll usually get a "clunk" when going into first.

Given the added fact that the 200 GBP box mentioned above is straight cut... I'd pass on it. The 3-synchro box is an acquired taste generally reserved for period correct restorations. Putting it under a modern A or A+ block for a street machine doesn't make sense to me, particularly with noisy straight cut gears.

[mini1071s]

Also the improvements which were built into the A+ design will not be there...

There was a 3 synchro ST SC gearset which went on ebay for 70 quid just a few days ago...

They are realy a specialist item, and although I would say not bad, compared to a later A+ box fitted with 4 synchro SC gears and uprated shafts, is no comparison.

Ooops, er, the A box was made out of better materials. The A+ box was made out of lesser materials and the engineers upgraded the sizes of parts to compensate. There are no real differences in the resulting strength.

You don't need to stop, as icklemini said, just double declutch. Easy when you know how to.

A 3 synchro box is a PITA though.

I disagree, the main benefit of the later A+ box is the removal of one of the holes in the third motion bearing retaining web, also the larger 3rd motion shaft, and the improved Idler bearing size..

I use to run A series boxes on my 1330, and was getting fed up rebuilding them because of that weakness.. I now use late A+ boxes for all higher performance gearbox requirements.

The shaft were increased in size due to the reduction in material quality.

You saying you had so much power from your engine you were cracking the third motion bearing retaing web? Or that the bearings are weaker?

A+ boxes are commone and much easier to get parts for, that's about it.

[mini1071s]

You don't need to stop, as icklemini said

No i didnt!!

Oops, I meant m1n1

[Jammy]

LOL! Nope, wrong again, Greydout said you had to be stationary!

[mini1071s]

LOL! Nope, wrong again, Greydout said you had to be stationary!

Er, confused now, I said as iklemini said, you dont' have to stop, just double declutch, not that ikclemini said you have to stop, and its more confused as it was m1n1 who said...ah who cares!

You know what I mean.

Our 67 has a non synchro first and you can engage it without any probs, you get used to matching speeds of the gears in the box, but as Guessworks said, (looks up to check he did say it), better off with a later box anyway.

[Guess-Works.com]

As you can see from the photo, the web has a weak spot... At that time, I was probably only putting 80/90 odd HP into the box.....