A new,n on Me,!!

[GT6 M]

Heres one I aint ever come across befoer
in OD and at below 2000 RPMs, foot oft pedal on cruise doon

and rev counter should read 2000 at 52 MPH
butt, its started to drop to 1200-1300 rpms as soon as throttle is off
{ rev counter is mechanical drov oft distributor, so its no electikery related,
as can happen wid electric types }

put throttle back on, revs come back up, and it drives wid oot slipping
above 2000,like 2200+, it dont doo it

cleaned oot all plugs int OD sump, clean as owt,
fresh oil, PSI reading 650 in 4th at 40 mph, or 2000 rpms

Im thinking Uni dirctional clutch, butt, may be wrong, wont be fust time

Looked every where ont tinterweb for similar symptom, but nowt there.

Any ideas befoer I pull the thingy

M

[garyf]

Could be a dodgy rev counter Marcus

Does the Rev counter react the same in direct 4th with no Overdrive engaged?  

[GT6 M]

Ello Gaz,nope its no the rev counter.
was oot last night, and it started dooing same after it got hot.

its not going oot of OD,
best way t, describe it is, wen ye put GN into neutral on a coast doon,
butt it dont go to idle,just drops 500 or so ish revs
ok in 4 th

most odd symptom,never come across this,n at all

M

[daver clasper]

Hi Marcus

O/D mechanicals a bit over my head, though had problems with my J Type not engaging sometimes/not disengaging/engaging even when disconnected.

Not cured by the simple stuff. Couldn't find anything about this online

Spoke to Dave Twigger at Overdrive Spares Rugby. Dead helpful and diagnosed the above as o rings in pressure relief valve hardeneded and not allowing movement, probably combined with solonoid gummed up.

He was spot on and a cheap though dead fiddley fix.

may be worth giving him a call

Dave  

[GT6 M]

Been oot the day, 140 mile roond trip
it starts when its well an truly hot

and, after some fart,n aboot, in gears in OD, 2,3,4
that its presure related,
as in OD 2, its happening right up at 4K revs, butt, flor it, its ok
3rd is aboot 3000 and 4th is 2000 ish

So, this I can fathom,
what I cant fathom, is why the revs drop to nearly idle
even in 2 0d, revs dropped to 1800-2000, in 4 th they go to 1200 ish

this I just cant fathom,

Will doo a PSI test when box is really hot, after a run
as it dont doo it wen cold
and I did test wen it wer cold

M

[efp]

Sorry M, still a little unclear here..  Do the revs really and audibly drop that far? Or just indicated?
Im a mechanical numpty compared too most of you, but my first thought was wear in the nylon square drive cable sockets on the dizzy or clock?  Happened to me.
Too simplistic?

[nang]

Something must be slipping...don't know what though.... Sorry. (shy)(shy)
Tony.

[GT6 M]

Moer investigatoinee,s t,day
its deffo coming oot of OD when its hot
and its slipping in /oot of OD upto 2000 ish revs in OD top
2nd od,it slips like mad
so too is 3 rd

Rev counter will drop  frae 2000 ish to 1200 is nearly right away
when its hot
Butt,speed still remains the same, this is the puzzling bit

Just had the sump off, and bunged in new O rings, ion the RH side one, looking frae the frunt
it seemed to be a wee bit looose
Oil was nice an clean, as just changed it a few weeks ago,
its no black as if the clutch bands were wearing away

went oot in it, it teks 24 ish miles for it to start its antics
and just started as I coming back into the toon

So the morrow, I,ll tek the solonoid off, see if thats at fault.

Greta GT6  { Nuala } was wid me t,day,  Maybe she chirp in, as She drov it 100 odd miles
ont the TR run t,day So second opinion on wots wot wont go amiss!!

As this is really puzzling

M

[Spider]

Marcus,
you could try putting a washer under the pressure relief valve, or remove one if there is one there already, then see if it happens at the same revs. I had a washer under the spring in one of mine and it started slipping out of o/d under acceleration and as soon as I lifted off throttle it kicked back in dropping the revs. I replaced washer to raise pressure relief point and it started behaving as it should. Might be useful as a diagnosis method to eliminate a pressure issue.
My only other idea I have (no expert on o/d) is that the holding coil on the solenoid is starting to break down, as it is nestling up against the g'box it will get quite warm and maybe having a temperature coefficient change in the resistance of the windings, especially if the insulation is old or been overheated at some point.

[RobPearce]

That was exactly the symptoms I had on my GT6's original D-type when it was knackered. Lack of oil pressure when hot meant it would slip under power or at full lift. Under power, the unidirectional clutch cuts in and provides direct drive. On lift-off, it doesn't.

When the unit had its original electrical problem, and the solenoid was rattling like a machine-gun, it would drive in direct top at 70 no problem but when you lifted off for a slip-road the engine revs would drop to idle, the oil pressure in the OD would fall off completely, the OD would then disengage properly back to direct, and the rear wheels would lose traction as they momentarily "locked" to idle speed (15mph).

[GT6 M]

I recalled yonks ago, wid a 2.5, that the thing would slip in reverse
if it had t ,shift some weight
IE, a trailer wid a car onit, up a steepish hill
butt, at the time,thought it were worn clutches int OD


Noo,moer I tink aboot it, it seems as its got sumat t,doo wid the orientatation of the teeth helix
and low pressure
as the teeth angle, is actually pulling the thing{ clutches } off wen in rev, or in my case, the rear end driving the OD
wen going forads, the angles are pushing the clutches into the brake band

so wid a low pressure, and the force oft gear teeth, the OD is going into free wheel mode
this is why its just happening below 2000 rpms, and higher in lower gears
as pump aint turning as fast

So, its maybe down to the O rings in the solly end, letting a PSI drop frae one port  { piston } to the other, { sump }

As ive checked all others, and OK

So will see wots wot when I get the solonoid off

im hoping its the O rings ont end gon hard / brittle,or damaged
failing that,its the clutch  lining thats dikee

Steeve Jackson came to similar conclusions too,
So, the Guru,s are deffo wrong on this one , that a OD cant free wheel, as others have  also found oot.

M

[Nick Jones]

D-type?  J-type?

Strange happenings for sure.

Nick

[GT6 M]

Update, efta trying diff things, easiest first, non worked
so had t, bite the bullet an pull the trans cover, that is a feat in its sell,
And me 2 piece one, the solonoid nut is well back frae the H frame,
so the lot ed t,come oot

Ont end oft solonoid, there 2 O rings, was think,n that they gon off
an letting oil escape at low pump speeds, which is = t, engine revs/gear speeds /ratios

O rings one ends looked OK,not got scuffs or crumbling,
butt, they wer flattened ont edges quite alott

an slack in their grooves, and measuresd 62 thou thickness
and slid oot the OD wid v v little resistance

bunged on some new O rings, 80  thou thick, and a good fit into OD
hoped it would cure me problemo

Oot for a test drive, should ev took me ear plugs, cos driving a GT wid the tunnel off is v v noisey, and v v drafty too

got over 20 miles,it wer ok
got to 30 miles, OK
got to 40 miles, and OD was really hot, so oil was as thin as it wer gonna get.
and,

Its working great, no dropping doon t, idle on run doon,
nee dropping oot at v v low revs,
teks 2,nd od at 1000 rpms nee bother at all

So, if any you lot suffer the same, check yer O rings, bung  some new,ns on
and a nice tight fit into OD .

M

[Dannyb]

Nice one. A good weekend then.

[GT6 M]

it were thee,s wee thingys ont end
and for good measure, ive just changed ooot the inner ,ns too
the ones ont inner pull rod

M