• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

A Type Overdrive "Refresh"

T

TRDejaVu

Guest
Guest
Offline
A Type Overdrive "Refresh"

I broke this away from the other current overdrive thread so as not to hijack it. Over the years I have overhauled most major components on these cars (engines, brakes, suspension etc etc.), but never a transmission. I consider this work as therapy so I am having a go at rebuilding an early TR6 O/D gearbox before replacing the existing unit in my non O/D TR4. The data plate shows that this O/D unit had been previously rebuilt.

I have it almost completely apart; the key word being "almost". As I don't have access to Mr. Churchill and his special tools I need to make up a rubber expansion tool to pull out the accumulator piston (small version without threaded insert). I am also trying to remove the 2 operating pistons but they are putting up a good fight. I have a couple of the online tip documents, but am open to all ideas; unfortunately I don't have a compressor.

When I removed the OD clutch housing I found a thrust washer broken into 8 pieces. Other than that, first impressions are that this is still in good condition. I am trying to find out what the wear limits are for the clutch material - anyone know?

100_1921.jpg
 

jjbunn

Jedi Knight
Offline
Re: A Type Overdrive "Refresh"

Is it as weird as it looks that the thrust washer broke into eight identical pieces? What's happened to do that?
 

2wrench

Luke Skywalker
Country flag
Offline
Re: A Type Overdrive "Refresh"

In my mind's eye, I seem to remember seeing, somewhere,
a washer similar in nature with "scores" in it that
could well replicate a destruction of this nature.
I just don't know where. Certainly not from the
inside of an overdrive, it seems.
Does look a little strange.
 

TheSearcherMan

Jedi Trainee
Offline
Re: A Type Overdrive "Refresh"

Clutch wear is not the only issue. They come apart probably as a result of age. It's a gamble not to replace it during a rebuild.
 

TR3driver

Great Pumpkin - R.I.P
Offline
Re: A Type Overdrive "Refresh"

Yup, it's scored like that, in an A-type OD. 4 on one side and 4 on the other, evenly spaced for 8 weak spots total. I don't recall which one offhand, maybe the one between the sprag clutch and the annulus, or the one inside the planetary gear assembly. In fact, now that I think about it, maybe there is more than one of them.

The scores are for oil circulation. Never seen one break all the way into 8 pieces, but I've seen 4 or 5. My theory is that when things get a bit loose, the clutch carrier bangs around at every shift and eventually breaks the washers.

I've never seen a clutch thickness spec, either new or wear limit. AFAIK it's like the main clutch, it's not worn out until the rivet heads are about to be exposed. And from your photo, it looks like there is plenty of material left.

I've always just grabbed the center post of the pistons with pliers or vice grips; don't recall ever having to resort to air pressure. Wiggle them around a bit, they should come out.
 
OP
D

DougF

Guest
Guest
Offline
Re: A Type Overdrive "Refresh"

Be sure to check the mating surfaces to that washer. Mine went and cut into the surface of the annulus. It will be going to Quantum for resurfacing.
 
OP
T

TRDejaVu

Guest
Guest
Offline
Re: A Type Overdrive "Refresh"

TR3driver said:
I've always just grabbed the center post of the pistons with pliers or vice grips; don't recall ever having to resort to air pressure. Wiggle them around a bit, they should come out.

The accumulator piston is now out, but the 2 operating pistons are not moving; in/out or rotating. I am going the PB Blaster route at this time.
 
OP
T

TRDejaVu

Guest
Guest
Offline
Re: A Type Overdrive "Refresh"

Well, the 2 operating pistons really didn't want to come out. I finally got to meet angelfj and we tried to coax the blighters out with his air supply (and some beer); but they weren't falling for that old trick. 2 more days of soaking (this time with Gibbs) as well as various heat/freeze combinations and then they started to move. They fought me all the way, but I finally out them out.

Looked for all the damage that must have been preventing them from moving and found nothing. There are some very minor little marks that I plan on cleaning with crocus paper and that is all.

These look like they will be a fight to get back in so I will have to make up a smaller version of a piston ring compressor and use plenty of lube. How "snug" should the piston be in the bore (without the o-ring)?
 

angelfj1

Yoda
Country flag
Offline
Re: A Type Overdrive "Refresh"

Ian: Oh, so that is the early type with the metal piston rings rather than the O-rings after all? What condition are the rings in?

Frank
 

TR3driver

Great Pumpkin - R.I.P
Offline
Re: A Type Overdrive "Refresh"

Don't know a spec for the clearance, but mine would slip easily in & out if you didn't get them cocked in the bore. Even with lube, though, it was easy to get them cocked, so it wasn't something I played with much.

A worm-type hose clamp makes an adequate (barely) ring compressor, if you do have the early version with the metal rings. The O-rings shouldn't need a compressor.

Last time I looked, you could buy a pair of O-ring type pistons for about the same price as a set of metal piston rings. If the rings need to be replaced, I'd change the pistons instead.
 
OP
T

TRDejaVu

Guest
Guest
Offline
Re: A Type Overdrive "Refresh"

I may not have explained it properly, but the pistons had the single (rubber?) o-ring, not the metal rings.

As to fit, these pistons are extremely "snug". When you say easily slip in and out, do you mean that if you temporarily fitted them WITHOUT the o-ring they would fall under their own weight, or would there be resistance due to the restriction of the displaced air only being able to escape through the oil-way? I hope that question came out clear.
 

TR3driver

Great Pumpkin - R.I.P
Offline
Re: A Type Overdrive "Refresh"

What I meant was that, with the rings removed (either metal or rubber, I have both), the pistons slip into the bores with only finger pressure. But that's entirely friction between the piston & bore, I didn't try blocking off the passageway to look for air resistance. And they wouldn't fall of their own weight.

Sounds like your OD may be less worn than mine were; so I'm not sure I'd try to relieve the bores or pistons any. Maybe polish them just a bit if there are rough spots.
 
Similar threads
Thread starter Title Forum Replies Date
71TR6 TR6 Type-J Overdrive identification Triumph 4
T TR2/3/3A A type overdrive hard engagement Triumph 28
R TR6 J-Type overdrive will not disengage when warm Triumph 8
RonC TR2/3/3A J Type Overdrive in TR3A Triumph 4
H TR4/4A A-type overdrive pump Triumph 4
Got_All_4 TR6 Refurbishing gearbox with A type overdrive Triumph 7
D TR2/3/3A Type A overdrive not engaging Triumph 0
D TR2/3/3A Type A overdrive not engaging Triumph 16
M TR4/4A A type Overdrive Oil Leak Fix Triumph 3
Graham H TR2/3/3A A type overdrive Triumph 6
KVH General TR Type A Laycock Overdrive Questions Triumph 8
C TR2/3/3A A-type overdrive drain plug oring Triumph 1
J TR4/4A TR4 A Type Overdrive Part mixup Triumph 4
CJD TR2/3/3A A type Overdrive Seal Triumph 9
T Spitfire J Type overdrive Triumph 2
T TR2/3/3A Question on A-type overdrive solenoid Triumph 21
BillyB62 TR2/3/3A Type A TR3 Overdrive Wiring Triumph 13
T TR2/3/3A Question on A type overdrive spec for "clutch movement from direct to overdrive" Triumph 7
M_Pied_Lourd TR6 J Type Overdrive High Pressure Filter Cap-Major Problem Triumph 6
R A Type Overdrive reassembly question Austin Healey 3
R TR2/3/3A A-Type overdrive question Triumph 8
T TR2/3/3A My A-Type overdrive rebuild project, some questions Triumph 36
T TR2/3/3A Will Spitfire D-type overdrive work in TR3 with TR4 transmission? Triumph 3
R Overdrive [Type A] brake ring gaskets Austin Healey 1
R TR2/3/3A Overdrive [Type A] Brake Ring Gaskets Triumph 14
J General TR D Type overdrive not working need suggestions Triumph 5
Gordon_Dedrick TR2/3/3A A type overdrive installation Triumph 7
T TR2/3/3A Type A Overdrive, Physical Differences between Roadster Brands? Triumph 2
T TR2/3/3A Type-A Overdrive Handling Differences Triumph 9
A TR5/TR250 A-type overdrive questions Triumph 25
71tr TR6 Overdrive Mount / J-type on A-type frame Triumph 1
D TR6 76 TR6 J Type Overdrive Triumph 7
Gordon_Dedrick Testing an A type overdrive Triumph 20
Simmo I need help with J Type Overdrive Triumph 15
Q "A" Type Overdrive Annulus End Float!! Triumph 4
D A type overdrive question. Triumph 3
John_Mc J-Type overdrive for sale on CL Triumph 4
KVH More on A Type The Overdrive Triumph 2
Coyote1 J Type Overdrive engage problem Triumph 3
J A Type Overdrive Triumph 17
K TR6 TR6 J Type Overdrive...Link to Schematic? Triumph 3
O J Type Overdrive Conversion Triumph 19
Marvin Gruber J type overdrive unit on BCF classifieds Triumph 2
HerronScott TR4/4A TR4A A-type overdrive and Moss Europe TR2-4A cat. Triumph 2
T A-type Overdrive & Gearbox Triumph 9
TR3TR6 J-type overdrive question Triumph 5
CinneaghTR A-type Overdrive Model Number Triumph 14
71tr J-type Overdrive Pressure Port Question Triumph 2
T A-type overdrive / gearbox trouble shooting Triumph 69
R_Lyle TR6 J-Type or A-Type Overdrive for 1972 TR6 Triumph 18

Similar threads

Top