auto boxes!
I have an issue with the auto box on my black pick up, when i took it out for a drive today the auto box wont shift above 3rd, the box was rebuilt about five years ago and at the time it done about 200miles, was in the workshop for the last four years, done about 50 miles last week was shifting into fourth ok, but then today wont??
any ideas where to look first? as you can tell i dont have much experience with auto boxes!
Hi Mick check the oil level hot (ATF) with engine running selector in "park" if early 460 G' box dipstick level should be half way between high and low mark...DO NOT overfill. also any vacuum leak will cause the valve on the side of the G'box with the vacuum pipe attached to fluctuate the shifting pattern / sequence..the feed to that valve comes from the throttle position so must be accurate rigging and no leaks...
Mick
Check the adjustment on the gearbox control cable , if it is too tight it may not drop into topgear . The vacuum operated device on the side of the g/box is the "modulating pressure valve" , this alters the gearbox mod pressure depending on engine load and helps to smooth the gearchange during heavy throttle use, but if my memory serves me it does not affect change points. If the diaphragm goes in the mod valve it has the nasty habit of sucking all the ATF out of your gearbox and into the inlet manifold resulting in a pure white James Bond style smoke screen. :o
HTH
Steve
Edited to say .... the above well meant comments only applied to those vehicles with a control cable ........... i really have been out of the game toooooooooo long. :oops: :lol:
Hi Mick Steve is correct regarding the modulation valve but the 460 series auto G'box does not have a control cable as on the G463/W124 G'box.....
Dohhh ! :oops: :oops: :oops:
Still in my defence it is 25 years since i last worked on a G. Is this the W4A018 box ?
Could be a sticking governor or one of those pesky little ball bearings in the valve body assembly , I would try a drain and refill with a fresh filter before any radical intervention.
Steve
hi mick, i don't know the g autobox at all but what you describe is something similar to what i had on a GM autobox only last year. if you're gear isn't changing when it heating up, check if the thermostat for the oil cooler (i'm assuming the 460 has one - yes?) is working. as mentioned, i had something similar last year and it was a sticky thermostat switch to the oil cooler. after a new one was fitted (and of course a change of the fluid and filter in case it lost its properties when it was overheated) no problems since. like i said, hope that is of help for what its worth/ph
Not sure there is a thermostat for the oil cooler, certainly it's not obvious. As far as gearbox control cable is concerned mine has a control rod which adjusts the shift points. It runs to the right side of the box (looking from the back), and is adjusted where it meets the throttle linkage at the back of the engine.
Hi it is a very basic mechanical G'box! the only thing electric is the park and neutral starter interface switch on the selector arm....very prone to erratic behavour if the filter is restricted..oil is old...vacuum is wrong....too much oil will blow the front seal and fill the bellhousing with ATF....and if the fording bung is in you only know when the starter stops working...
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hi guys, thanks for all the replies, was racing an irish championship enduro the weekend so didnt get a chance to look at it over the weekend.
had a quick look this evening after work, all the vacuum lines are connected and no leaks, it will change into 4th when cold, but as soon as it heats up (few minutes driving) it wont change to 4th, the oil level is a bit low, so will pick up some atf tomorrow and top it up.
which type of atf should i get? dextron 2,3,4?