87 Hilux auto won't shift into OD when "cold"

[bluemountains]

Hi Luxers,

I have a 1987 YN58 Hilux XCab which I bought last December, in peak summer. As the weather has cooled off, it has refused to shift into OD (or 4th if you like) until it's been driven 6km. Very repeatable. Otherwise behaves normally. Once warmed up, OD lockout switch on the shift lever behaves normally. The temp gauge indicates in the middle of the range after about 1-2km.

My mecho tells me this behaviour is normal. Says it is to ensure cat converter comes up to operating temp quickly to reduce emissions. Plausible. However, the owner's manual contains no mention of OD being unavailable until the engine/trans are up to a certain temperature.

I've installed an LPG fuel system on this Hilux, so the cat converter really doesn't have much to do. I live up in the Blue Mountains and my morning drive is all downhill, so I kinda miss OD for those first 6km. 3000RPM at 80km/h is a bit annoying.

Transmission is Aisin Warner 03-71, which I understand does have a connection to sense engine coolant temperature.

IF this is normal behaviour, and IF 03-71 has a coolant temp sensor connection, I ought to be able to 'fake out' the transmission so it thinks the engine coolant is up to operating temp.

Can anyone help me with which wire to this trans tells it about engine temp and what the state on that wire is at when engine is at operating temp?

Thanksabunch!

-Brian

Edited June 7, 2013 by bluemountains

[CONROD]

There is nothing wrong with it!!!!

Be patient untill it warms up.

Its also there to prevent the COLD engine from pulling a too higher gear whilst cold.

Toyota is not the only ones to do this.By playing around with it and by-passing/altering certain features you will create more problems than its worth,especially having a COLD transmission in overdrive and trying to get it to pull,let it do what it is designed to do.

Edited June 7, 2013 by CONROD

[bluemountains]

Thanks for that. I would hate to stuff up this Hilux, it's a pretty tidy example. Only 172,000km when I got it- last owner was an 85 yr old bloke who had used it only a couple times a year for his Rotary Club stuff. He'd only put 20,000 km on it in the last 20 yrs. I had to replace the master cylinder & radiator due to corrosion caused by the thing not being used enough.

I guess I'll just have to be annoyed for 6km every day until the weather warms up!

Thanks. :)

[bluemountains]

Did a lot of sniffing around- seems that there's no temp control which prevents the Aisin-Warner 03-71 automatic from selecting OD when cold. If it won't shift into OD, the problem is the OD lockout solenoid valve. If it won't shift into OD when cold, the solenoid valve is sticking & frees up when warm.

The solenoid valve & cable assy is detailed in this dwg & labelled 85420B

The actual Toyota part number is 85420-20050.

The problem on my Hilux continued to get worse- at first, it was only sticking shut for the first 7km after a cold start. It got progressively worse until I had to drive it 30+ km before it would select OD.

A replacement OD lockout solenoid is horrifically expensive. Upwards of $350 at a Toyota dealer. Found one for as low as $134 from this mob.

However, I really have no use for the OD lockout function. Really annoyed me to have to part with even $134 to restore the feature.

I did more sniffing around. So it happens, the AW 03-71 was used on some Volvo 700 series sedans in the late 1980s. The OD lockout solenoid fails on those Volvos, too. A Volvo club in the UK details the problem here.

If you really want the OD lockout feature restored, you can buy a new solenoid. If, like me, you don't give a crap, you can buy a solenoid eliminator blockoff plate from these guys for $US40 plus shipping.

If you're even more like me (read: cheaper than dirt), you can discard the inner O-ring seal & cut a slot between the fluid inlet & outlet with your Dremel & a thin grinding wheel:

Just cut off the wire on the top of the solenoid & bin it.

NOTES:

a) Clean the gack & goo from around the solenoid before removing it- it's on an upward facing surface & there will be a lot of dirt & gunk around it. You don't want 25 years of mung to drop into the fluid circuits in the slushbox when you remove the solenoid valve!

B) There's very little clearance for a spanner to get at the bolts which hold the solenoid valve on. You may have to release the transmission support crossmember & drop the tailshaft housing down a couple inches to get access. With some WD40 and a few hammer taps on the spanner, I managed to get the bolts on mine out without dropping the crossmember but very nearly rounded off the bolt head on the forward of the two bolts. They're 12mm hex heads- and are much tighter than they ever should be. May have to do with steel bolts in aluminum threads & 25 years worth of no doing much.

The slushbox now selects OD by itself, even when cold. However, the OD lockout switch on the gear selector (naturally) now no longer works. And not a single crap was given!

Cheers

-Brian

Edited August 28, 2013 by bluemountains