AP A-series autobox rebuild/strengthen

[OneCarefulOwner]

I asked this a while back on t' old board, but the answers have been lost from my mind so I'm asking again

My S1 Allegro Walter has a lovely sweet-running 1275cc A-series connected to a mostly-reliable AP autobox, but occasionally it seems like there's a bit of slip changing from 2nd to 3rd, especially when cold. As my commute involves climbing a hill immediately (both ways, honestly!), this can lead to "hilarious" over-revving as I try to keep up with traffic. I'm not sure, but I think it may be related to the one time the engine stalled from overheating & I got so flustered that I changed into gear then floored it before the gears had properly engaged... Cue nasty graunching noises! I can't be sure though because I didn't really pay as much attention, but if it was there before it's worse now so it still needs dealing with.

Is rebuilding one of these 'boxes a viable job for a hobbyist with access to cool tools but only his own enthusiasm to guide him? Is it also possible to uprate them in any way, as I'd like to try and squeeze a bit more power out of the engine if I can... Or even just free up what's already available by lengthening the final drive? My 998cc A+ Allegro manual will exceed the legal limit & happily sit there for miles, but I have trouble getting past 60 in the auto.

[JPB]

I fail to see why an epicyclic transmission would make "graunching" noises since the "gears" are all in constant engagement, the fluid path being the only thing that changes as you move the shifter, could the actual problem be something bizarre but that happens occasionally such as a loose or worn drive flange?

[bnicho]

Hi,

My Moke is powered by an ex-Metro 1275 A+ with an AP Auto. It's bee trouble-free for around 20,000miles of occasional use now. I even off-road it and a tow small trailers with it.

I haven't had any first hand experience rebuilding the boxes, but two mates have sucessfully rebuilt them at home.

The symptoms you describe is called "flaring" and can happen due to dirt lodging in the valve body, or it can be a slipping band (less likely).

What oil are you using in the box and how often are you changing it? Using a syntheic oil can cause massive problems with the gearbox, as can leaving it too long between changes.

There is a forum for the AP auto here. I'd suggest having a read and possibly joining.

http://autominiregister.proboards.com/index.cgi

Cheers,

[OneCarefulOwner]

I fail to see why an epicyclic transmission would make "graunching" noises since the "gears" are all in constant engagement, the fluid path being the only thing that changes as you move the shifter, could the actual problem be something bizarre but that happens occasionally such as a loose or worn drive flange?

I dare you to rev the engine past 3k then shift into gear; you'll hear the noise yourself then! Something has to give in those situations, and as I was completely static I failed to achieve wheelspin, ergo something inside went "graunch"!

When I got the car (last August) it had been undriven for 4 years. I considered having the oil flushed but was advised against it for fear of damaging the gearbox, so we just drained & replaced with 15W40 non-synthetic. Doesn't mean there isn't schmutz in there though, which could have worked around the oilways since being returned to service. I've not kept close tabs on the mileage but I doubt it's done more than 1k, it's only left London once & it shares commuting duties with many other cars! Still, considering it's gone from ignored to commuter I'm planning for it to receive some more intensive recommissioning at some point… Assuming I don't do other more unspeakable things to it instead

[harvey]

IIRC (and the info came via a thread that JPB found) the upgrade involved machining down the pressure plate and steel plates in the clutch pack to enable one extra friction plate to be added. I know there are special tools to do an overhaul on them, but I can't remember if those tools are absolutley necessary or the job can be done without using them. I did a few years back, with varying degrees of success (probably not surprising as I was only about 16 at the time) but later I worked at an Austin/Morris dealer and have been friends since then with one of the blokes who was working there at the time, and any that needed doing since then he's done.

[Mrotwoman]

There is a forum for a gearbox ?

Some folk need to get out more

[JPB]

There's also a forum for people who collect Biro refills, but anyone on there with a similar user name to the one I have on here is there purely by coincidence.

I remember that thread, Harvey. Weren't later examples of the AP transmission modified in a similar way for production and didn't the idea come from the version found in the cars (Lancia Betas, etc.) that used the AP unit - running in ATF - for applications that saw it attached to the end of an engine rather than swimming about in the filth of its sump?

[OneCarefulOwner]

There is a forum for a gearbox ?

Some folk need to get out more

In fairness, the AP gearboxes for the A and E series are/were epic, and massively advanced at the time of release.

Harvey, does this guy do commissioned work, or just jobs-for-friends? Enthusiastic as I am, I don't wanna **** a decent engine if there's a cheaper option - but I can't afford for a major gearbox shop to have a look, especially as I doubt they'll know much more than I do about the 45 year old tech in my 35 year old 'box!

[harvey]

There is a forum for a gearbox ?

Some folk need to get out more

I keep telling myself that.....

[bnicho]

The reason for the development of a forum for this gearbox is simple.

People like me were sick and tired of the misinformation about this gearbox.

If you metion an auto problem on most of the mainstream Mini forums, you are told "It's unreliable, throw it away and put a manual in". Hence the people with the knowledge to help stop posting. The result is knowledge lost.

The Auto Mini Forum was started by a member of the old PC forum with an Auto Mini. This lady was unable to drive a manual due to a disability. She did not want to give up her Mini when the Auto box died due to a mechanic putting synthetic oil in it. I am a mod on that forum too, so be nice!

As for the graunch noise, I have achieved that a few times, through impatience. Just yesterday I jammed it in drive and put my foot down to get into a gap in the traffic before the gearbox had engaged fully.

Ywes, teh later boxes (like my 1990 unit) had the triple friction plates from the factory, which makes it stronger.

There is a lot of debate on the Auto Mini Forum about oils. Some say 10W-40 non-synthetic is fine in the Auto, others say it causes problems. I've always stuck with 20W-50 personally.

I would suggest changing to a mineral 20W-50 oil (eg: old-school Castrol GTX or equivalent) in your Allegro now, then changing it again in another 1000 miles. That may give it enough of a flush out to clear the problem.

Cheers,