"Peter Frost" <peterfrost@cph-metronet.dk> skrev i en meddelelse
news:452224dd$0$49198$14726298@news.sunsite.dk...
> Hej gruppe...
>
> Jeg har en Volvo 850 10/93 94 model, med smalle forlygter osv. Gear'et
> hedder AW 50-42 LE. På min årsmodel er denne gearkasse med lock-up på 2.,
> 3. og 4. gear. Bilen har kørt 203.000 km.
>
> Symtomerne er følgende. Når bilen har stået natten over, har den en
> tendens til at skifte lidt hårdt de første 100 meter. En enkel morgen
> lavede den samme som de "normale" symtomer som vil blive beskrevet ned
> for, uden at jeg havde kørt, dvs jeg startede motoren, satte gearvælgeren
> i R, for at bakke lidt tilbage, for at kunne komme ud af min p-plads. Her
> begyndte bilen at ryste, og motoren hævede omdrejninger, for ikke at blive
> kvalt af gear'et. Præcis som hvis man i en manuelgear bil, bremser uden at
> trykke koblingen ned. Disse fortsatte også ved kørsel, efter 1 km ca,
> kunne jeg i et lyskryds sætte gear-vælgeren i P og slukke motoren, da jeg
> startede igen, og satte gear-vægleren i D, virkede alt som det plejer.
>
> Næste fejl jeg har oplevet er hvis man kort efter start accelere godt, og
> så bremser ned for rødt, "kobler" den igen ikke ud, bilen ryster meget, og
> motor øger omdr. Her sætter jeg gear-vælgeren i N, og ved grønt i D, her
> hakker den lidt indtil den skifter til 2. gear, og så oplever jeg intet
> forkert før næste gang.
>
> En enkelt gang har jeg kunne aflæse fejlen : Lock-up, Slips or Disengages.
> Men ellers giver disse fejl ikke fejlkoder i diagnose computeren.
>
> For mig virker det som om gearkassen ikke "kobler ud" og fejlende sker
> altid ved kold gear olie. Olie standen er i følge oliepinden fin, måde ved
> kold og varm. Målingen er som instruktionsbogen dikteret, målt med motoren
> i tomgang.
>
> Jeg talte med AutomatGear Centeret i Gilleje der mente det nok vikke koste
> en renovering, som han rundregnet maks skulle ha 20.000 kr for. Pengende
> har jeg så sat på en konto, og vil helst ikke røre dem, men kan det gøres
> billigere kan jeg få råd til nyt objektiv til kamera'et.
>
> Mine spørgsmål er til dem der kender lidt til automatgear, hvad kan der
> være galt, og hvad vil det koste at få lavet, og er en renovering nok,
> eller er det muligvis "bare" magnetventiler i styreboksen, og olie-skift
> der skal til her ?
>
> Envidere er der nogle der har erfaringer med det ville kunne betale sig at
> køre til Volvo-land, Sveige, og få det lavet ?
>
> Håber virkelig på lidt hjælp her, for alle jeg snakker med der ved noget,
> føler jeg bare vil sælge mig en masse, jeg reelt set ikke har behov for.
>
> På forhånd tak !
Sådan virker en automatkasse, her specifikt Jaguar B&W. Det virker som om
funktionen af ventilerne afgør om skidtet virker:
Series 3 XJ6, Transmission, Trans Theory
This bit on trans theory was sent to me by a true tranmission repair
specialist. It was originally a reply to a question on Borg Warner troubles.
Dear Mike: This is going to be a long story. Not being there to road test
and check the car out, the next best thing is to explain how it is supposed
to work and see if you can decide what the problem is. You're there; I'm
not. Sit back, read, and check this out: There are 3 basic principles that
come into play and their relationship to each other is critical for
long-term durability of the transmission. For teaching purposes I will use
round, estimated figures; not the actual pressures in a BW. PRINCIPLE ONE:
Governor pressure is approximately 1 PSI for each MPH of road speed. 10 PSI
governor = 10 MPH. 30 PSI = 30 MPH. 0 PSI means you are standing still.
Pretty simple concept, huh? PRINCIPLE TWO: Throttle pressure (or shifting
pressure as the Britts may call it) is just like governor pressure, but it
is proportional to the amount of throttle the engine is given. No throttle
pressure = no throttle. 50% throttle = 50% throttle pressure (say, 50 PSI).
100% throttle = 100% throttle pressure, or 100 PSI. BRIEF INTERMISSION: Now
this is where it gets hairy. It is important to understand a balanced valve.
It goes by many names, but the principle is the same. Balanced, or
regulating valves do just that; regulate a pressure to a pressure that keeps
the valve balanced. Just like the oil pump pressure regulator valve set up
in an engine. If the oil pump volume is more than needed, excess pressure is
exhausted. Conversely, if the oil pump speed, or volume, drops; then the
valve that was partially open exhausting oil, now closes off the exhaust to
maintain pressure. At any given steady volume, or any given spring tension
that "balances" the valve; the valve will always seek a state of
equilibrium. Change the spring tension or the amount of oil being supplied
to the valve, the balance is upset and the valve will open or close the oil
supply, depending on the system's needs. This is why you either put a
stronger spring in, or shim the current spring in an engine's oil pump to
increase oil presssure sometimes. You are changing the balance. Conversely,
if you cut a coil or two off of that same spring, you would run lower oil
pressure. If you can feature this principle, the rest is downhill from here.
Here's the revelation: The governor and the throttle valve are both balanced
valves. The governor has a variable spring called centrifugal force. As
output shaft speed increases, so does the "tension" on the force that
balances that valve. So pressure rises and falls with output shaft RPM. The
throttle valve has a real spring with a fixed tension. The trick here is
they make the spring seat move with throttle opening by way of the infamous
throttle cable that goes down to the trans. This cable works a cam-like
device that mashes in on the throttle valve spring to increase the spring
tension. When you let off the throttle, the throttle valve (TV from now on)
lets off the spring and the TV pressure drops. I hope I have not been too
simplistic so far. A lot of this may be common knowledge to you, but I am
trying to make sure you and I are on the same page because the next part is
where most techs screw up. If you have access to the oil schematics of any
automatic transmission (especially a BW 65 or 66) find the 2-3 shift valve.
It has a spring under this valve that takes 25 PSI of governor pressure to
depress the 2-3 shift valve down to the 3rd gear position. If this was all
that we had to worry about, life would be wonderful and Clinton would not
have been elected. But life is not that simple. This brings me to: PRINCIPLE
THREE: All of the clutches and bands are hydraulically applied by an oil
pressure called mainline, or, control pressure. I prefer to call it
mainline. The more torque the engine is producing, the more mainline
pressure you need to keep the clutches and bands engaged solidly and not
slip under torque. At light throttle, or when your grandmother is driving,
you only need minimal mainline pressure to do the same job. If the mainline
pressure was to remain high during Grandma's trip to the store, the
excessively high mainline pressure would slam each band and clutch on hard
enough for her to add a tube of Denture Cream to her shopping list. It
didn't take long for the God of transmission engineering to figure out that
mainline pressure should somehow be proportional to the amount of torque
flowing through the transmission. This is why light throttle shifts are
softer than heavy throttle shifts. He decided that us knowing how a balanced
valve worked was too easy. He had a brainstorm one day and said
"Hey.......let's really confuse the hell out of them and have the pressure
off of a balance valve control ANOTHER balanced valve." So with that thought
in mind, look at any automatic transmission oil circuit schematics
(including B/W) and you will see the yellow (TV) pressure also goes to the
spring end of the main pressure regulating valve. When TV pressure goes up,
so does mainline. If TV pressure goes down, so does mainline. TV pressure
actually "boosts" the tension of the main pressure regulating spring. As is
if this is not confusing enough, remember earlier when I said the 2-3 shift
valve had a calibrated spring to take 25 PSI of governor pressure to move
the valve to the 3rd gear position? Well........TV pressure also is routed
to the spring end of both the 1-2 and 2-3 shift valve. What this means is
this: With absolutely no TV pressure 1-2 occurs about 10 MPH and the 2-3
shift occurs at 25 MPH. As you give the vehicle more throttle, TV pressure
rises to provide TWO (count them, 2) functions. Function 1 is to raise
mainline pressure to keep the clutches and bands from slipping and giving an
acceptable shift feel. Function 2 is to delay the shifts by this technique:
With more throttle, the governor pressure now has to overcome the 25 PSI
spring under the 2-3 shift valve AND....AND...AND...whatever amount of TV
pressure that is assisting the 2-3 shift valve spring holding the 2-3 shift
valve in the second gear position! So if there is 15 PSI of TV, plus the 25
PSI calibrated shift valve spring, keeping the 2-3 shift valve in the 2nd
gear position; it would now take 40 PSI (25+15=40) of governor pressure to
move the 2-3 shift valve to the 3rd gear position. That means the car would
have to be doing 40 MPH, or faster for a 2-3 shift to occur. If you are
doing just 38 MPH and wondering "Why the heck hasn't this thing shifted
yet?", by letting off the throttle you just dropped TV pressure so that the
current governor pressure is high enough to overcome the 2-3 shift valve
spring and what little (if any) TV pressure under the 2-3 shift valve.
Starting to make sense? Now that you have read my novel, let me get to the
meat of the matter. It's important to know why, because then you can know
how. The valves (all of them) in this transmission are very prone to
"sticking". The most active valves will be the most likely to stick (TV,
governor, mainline pressure regulator), although the most common is the
governor valve. Symptoms of a sticking governor valve are: Late shifts.
Stacked shifts. 2nd or 3rd gear starts from a stand still. In general,
erratic shifting that is often transmission temperature related. Here's the
real comedy of errors: You come to a stop and Governor pressure is zero,
like it's supposed to be. You take off and the governor pressure curve goes
flat at some point because the valve just hung-no upshift-you back off the
throttle and it upshifts. You back off the TV cable adjustment to get an
earlier shift and it is of little, if any, help. You back it off all the way
to get the earliest possible shifts and it barely acceptable. You (or the
tranny shop) ships the vehicle out. BIG MISTAKE. REALLY BIG. In an effort to
get shifts on time, you just dropped mainline and mainline boost oil
pressure down to where there is not enough mainline to hold the clutches and
bands engaged at higher throttle openings. The unit slips and it eventually
comes back burned up from the low mainline pressure. Everybody is pissed.
The customer, transmission guy, and you. Finger pointing and reputation
bashing in it's finest hour. I could go on for pages and pages on this
scenario and about half a dozen other ones that commonly happen to the BW in
Jags. Have you had any of them lose reverse yet? That's another novel in of
itself. By now you are probably saying "Well, Larry, that's all neat; thanks
for explaining how transmission oil circuitry works and why they shift late,
but how the heck do I fix it?" Hey, Mike; governors wear out like many other
parts on a car. Buy cheap insurance and put a BRAND NEW governor on every
rebuild. Sell it to the customer. I have even sold brand new valve bodies.
If they don't buy it up front, you'll get hung with either buying it for
them under warranty, or having one hot customer. Burned up clutches and
bands in a BW is the resultant of a hydraulic malfunction condition. Usually
low mainline pressure, or wrong-gear starts. A rebuild only puts the
transmission in the same condition it was in before it failed. Not
correcting the hydraulic problem is the same as putting new pads and shoes
on a vehicle that has leaked all of the brake fluid out, or putting air in a
tire with a nail in it. Drive the car around and you decide. Hint: The TV
cable is set right when full throttle coincides with the TV cable pulled all
the way out and you can get a 2-1 downshift when you floorboard the throttle
after a minimum throttle 1-2 upshift. Let me know if I can be of any more
help. Larry Bloodworth