I have an L28D in my '67 Benz S Class. ENgine is fine but auto box is stuck in 1st and secod ratio. it revs hard and then lurches into second then won't change again. mechanic checked the vaccum and said fine ( thanks howler ) So any other ideas what could be a miss?
Could it be electrical.
They have bought a new box thats coming tomorrow and I am hoping to god that it solves to problem but I would like to know what the problem might be.
we tried changing the plates in the box but the symptoms were the same.
vacum modulator-screwed in to far into box.
the pin comes in different lengths,normally set when box was assembled.
if the valve body was removed to service it may have moved to towards the modulator.
fix add a washer and road test.
check that you got a diesel vac modulator.
normally a deisel type fitted to a gas engine causes this problem.
Now, is the Electric kick down in the actual gearbox unit itself (ie the bit my mechanic has just ordered from BKK) or is it some separate black box somewhere in the car?
And you beleive that if the kickdown unit was blown or damaged in someway then it would not change up through the box?
I am concerned that I am gonna shell out 600 bucks for a gearbox and the problem is somewhere else.
You see, first he tried changeing the clutch plates saying they were worn due to lack of fluid. I was willing to accept that. But when test driving that fix the symptoms were unchanged, I was more convinced that it was electrical. I don't know if the "black boxes" are in the gearbox itself but if they are not, I have a horrible feeling that I don't need a new gearbox but do need an auto electrician...
THe worst part, this dude is a referal from a good friend. How do you proceed from here...?
If the mechanic doesn't know where the modulator or the kick-down is, maybe you should talk to another mechanic? Maybe good to check what Dave mentioned before swapping the box - could be cheaper.
so are you saying those to items are not in the main 'box housing?
I'm spending most of my time in hospital or between there and home these days due to an unrelated accident so I can't chop and change mechanic as easily as when I am healthy and mobile.
So with that in mind, can someone please tell me, are all the bits that could go wrong in that main 'box so what ever it is it is likley to be resolved by a swap out. Or are there many ancciliary parts that also come into the equation with these symptoms?
kick down.solinoid.side of transmision.
2 wires only works when electricity in applied.pushes a rod into the trans.
unpluged it should retract.
vac tests for dumies without a gauge.
no vac-disconect hose-hard shift and wont go in to 3rd gear untill its near full speed.[on jack stands].50-70 mph
full vac.hose direct conected from alterator to mudulator.
very soft shift.shifts into 3rd gear.20-40 mph
governor test.
it might have stuff in the the valves.this spins with the rear drive shaft.
normally if the gov is stuck it wont up shift.SOME HAVE A STRAINER.
how trans work
several important pressures.
modulator pressure.[trottle-load].this changes the line or pump pressure to cope with added loads.
govenor pressure.a flyweight on the drive shaft opens a valve to allow line pressure into the gov circuit.at a set point the gov equals line pressure,might be 100 mph.this is normally found when the trans shifts into top gear with full throttle and kick down as a saftey.
valve chest-spool valves. think of cotton real.
on one end of the spool is line pressure
the other is govenor.
the spools have different surface area and springs.there are many inside.some are timing valves to give soft changes up and down.etc etc.
as gov pressure increases the spools move at the right pressure points to give shift points.
on the side of the box is several pressure plugs for test pressure gauges.GOV-LINE-ETC
worn clutches they normall slip under load or lock up.if tested on a stands with no load they normall will go as normal just slow to engage.
worn/loose 2nd gear brake band will keep the car in first untill 3rd gear is selected.this band is adjusted and easy to test.too tight it will engage 2 gears and lock the box.this band is used in reverse.
also a locked 1st gear overrun clutch can also give 2 gears at same time.
to test drive in drive 1st gear and lift of throttle car will coast in a neutral.
you need full vac on the modulator[air vent blocked] or the electric kick down aplied to do this.
held first gear is different,an extra clutch is used.
same deal with 4th gear in overdrive models.it will run in up to 3rd gear and slip badly in top.
WCJR31 Skyline.3.0 manual.wagon
R31 SKYLINE/Passage GT/PINTARA
LPG Ford Falcon 99-06 93 Disco
Local Shire Southern Zone Mechanic.
Thanks a million! Have a virtual pint of amber nectare on me. That is lots to think about and IF I get there tonight and it's not sorted, I will have some good questions to ask.
Also sounds like the problem areas are ALL in the box itself so swapping would be a logical cure even if it means we don't know the exact problem.
I just want my car back usable agian. After leaving it at the garage I went home and blew myself up in the garden after 4 days in hospital I have to drive to have my dressings changed twice daily. in a broad seated comfy auto, that is less of an ordeal than in a 1976 corona manual.
) So any other ideas what could be a miss?
