Drive problem

[Bathafarn]

A week ago my wife noticed the KZN130 was changing gears a little later than usual. I checked the fluid and it was a bit burnt looking so I drained what I could out of the system by removing the plug and was surprised to get 5L out of it, as most posts tell me to expect only 2.5L. Anyway, the used oil went straight into the fuel tank and I refilled using the recommended Comma ATM mineral oil. I put 5L in as that is what had come out and the level seemed to be just right.
Drove it for a couple of days but it was still revving higher than previously before changing up. Yesterday it lost drive in 2WD mode and will only move very slowly - zimmer frame pace - and at high revs when in 4WD.
I don't know if it would be the auto gearbox, the transfer box, the differential or a simple electrical problem. The engine is mint, I've had it for 4 years and apart from a cylinder head replacement 2 years ago that I did myself successfully, it has been no problem and has 11 months MOT on it too! As I am out of work I can't pay big money for a garage diagnosis and replacement at a cost of more than the vehicle is worth so if anyone could give some pointers as to likely issues I will try to self assess and if I am able, do the job at home.

[BUSHWHACKER]

Sounds to me like you drained the engine oil not the transmission fluid.

and this bit sounds worrying too, "...the used oil went straight into the fuel tank....." ??????

Where exactly did you drain the oil from? And where/how exactly did you re-fill?

[Bathafarn]

Definately not the engine oil that was drained. I've changed that typically every 6 months or so for the last 4 years. Similarly the auto oil - which I know should be a red colour - I had changed a year ago as part of a service and has been periodically checked over the years at cold and at hot temperatures with the engine running after cycling through he gearbox.
What I meant was it was not red but a burnt blackish colour, but was the expected viscosity. I filled via the automatic transmission dipstick at the back of the engine bay and not the engine oil dipstick which is yellow and more towards the front of the car. The oil now in there is a nice colour and there appears to be no ingress of coolant or any other fluids. It just doesn't go.

[Bathafarn]

Forgot to mention about the oil added to the fuel tank which you asked about. I have always added any engine oil or transmission oil from any of my vehicles straight into the Hilux tank after running through an old sock. It actually has seen very little diesel in the last 4 years and with 20 litres of vegetable oil available at Costco for £18.45 it makes the miles cheaper!

[BUSHWHACKER]

Wel something doesn't seem right.
If you had the ATF changed only 12 months ago, then it should still be red and clean, unless you've done over 100k miles in that time.
If you managed to drain approximately five litres out of the transmission's drain hole and the fluid was burnt, it seems the transmission was overfilled and has caused some internal damage possibly to the fluid pump.

Did you check the fluid level with the engine idling?

[Bathafarn]

Yes, the engine was running and I had cycled through the gears whilst depressing the footbrake and with the handbrake active.

[BUSHWHACKER]

It's possible that the torque converter has gone bad if there's no drive and the fluid level is correct. Either way the transmission will need to come off.

[Bathafarn]

I was hoping there might be an easier and cheaper solution but I guess you are right. I think before I go ahead I would like to explore a full AT oil replacement as I understand only a 1/4 to a 1/3 of the fluid comes out from the drain plug. I am probably clutching at straws, but they are at lot more available and at a much better price than replacement gearboxes!

No other possibilities?

[Bathafarn]

Anyone else have any suggestions before I empty the autobox sump again?

[Albannach]

Mine did what you describe last year, the box had to be re-built.

[TonyN]

You get at least 1/2 the oil out when draining sump.

I'd go for a working used box and torque converter, its the cheapest option.

[Kpauto]

might run like shit ifyou put any old crap in the fuel tank!

[Bathafarn]

The engine never misses a beat. Transmission oil - like sunflower, vegetable, peanut, walnut etc. has virtually the same calorific value as diesel so burns just fine. Diesel is the name of the man who invented the diesel engine and there was of course no derv available at theis time.

[Bathafarn]

Drained the autobox again and despite the 4.5 litres of fresh oil that went in just a few days ago the 5 litres that came out looked really dirty. Decided to remove the sump and inspect the filter but could not get it out after usdoing all the bolts due to the exhaust being inconviently in the way. Having no ramp or pit to work from I was fed up and a bit dizzy so I reseated the sump and topped up with yet more new mineral oil. It did move - without too much enthusiasm - after this but it got dark so I packed it in and was hoping for some input from our Antipidean friends before dawn. The question is this:

If I now have a small amount of 2WD where before I had none after adding fresh oil, should I persist with removing the sump and changing/cleaning the filter and possibly doing a total oil renew using the 2 buckets method I have read up on on this site?

Any and all help welcomed.

As a P.S. If I did manage to get hold of a replacement transmission, how much is it likely to cost to perform a changeover? Looks too heavy a job to do on my own without knowledge and a ramp, although I would be willing to help/do a Hilux head in return for help in doing mine. If Nothing comes of this there will soon be an excellent 3.0TD engine available in the North Wales area for anyone interested!

[BUSHWHACKER]

I'd love to know how you manage to get 4.5 litres of fluid out via the drain plug hole.