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The Automatic Transmission Thread


twisty
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I killed my old auto (RE4R03) recently and have eventually ended up with a Wholesale Autos Extreme AT, Nomad valve body and HD bronzed TC. I’ve learnt a bit about my auto gearbox recently and thought I’d share what I learnt.

They are better than manuals.

Heat will kill automatic transmission quickly (as will water).

I’ve had many autos and prefer them to manuals on the road and at the farm. For me the gear changes were sluggish in the old AT and it was a disappointment from the very start. Although the new AT is excellent, half the problem is the auto's TCU (Transmission Control Unit) and I still find myself shifting down to second for a hill if the ecu hasn’t shifted yet. Or for complete control in the city, select “Hold” and “drive it like a manual”.

The AT Power switch (next to the gear selector) has three positions. Centre is “Auto” (economy), forward is “Power” (sport) and back is “Hold”. Hold, from the owner’s manual, is used for standing starts in slippery conditions. For me, around town I always drive in “Power” mode and O/D off. Sometimes I’ll knock it back to 2nd for a hill if the ecu hasn’t shifted. Highway O/D is on. In the bush “Hold” and drive it like a manual.

Most recommend fully synthetic oil such as Castrol Transmax Z. Service kit from repco included mesh filter in housing and pan gasket $50. 8 litres of castrol transmax z $120 from castrol (and they sell it in 20l drums @ $299.50). Transmax z is a honey colour (not green or red). Apparently they changed the colour because it was being confused with radiator coolant.

Yeah ... beef up the cooling. Davies Craig make a few oil coolers. The cooler is mounted with plastic "spikes" and spacers through the radiator. Additional hydraulic lines are run so the new cooler and radiator oil cooler flow in series. You can also bypass the radiator oil cooler. Beware if you live in a cold climate (snow) the AT uses the radiator to help heat the ATF to operating temp so O/D can be selected.

Problems

Anyone with a factory tow pack has a vehicle that’s probably done a bit of towing. They’re a good box, but like everything, they wear. A good service will cost about $3-500 (if you get a flush as well). Aftermarket oil cooler about $150. If your tired auto doesn’t respond to this then it gets expensive. The bits that wear are the clutches and valves. The valves operate the clutches that engage the gears. If you replace the valve body with a shiny new one it will only put more pressure on already worn clutches.

My stupid plastic radiator sprung an internal leak in the transmission cooler section, pressurised the ATF system and mixed water with the ATF, then the AT died (took about two months). On the GU the breathers are mounted inside the LH guard and can't been seen. Eventually I had a "mud" like liquid throughout the LH wheel arch that smelt and felt of oil but no obvious cause (till now).

Solutions

Replace the stupid plastic radiator with the biggest, toughest, Australian made copper radiator you can ($1K). Why copper, well, it can be soldered (repaired) in the bush. Aluminium needs a tig welder. WHO TAKES THAT CAMPING?

Ignore the initial problem and drive till the AT dies. $5K and ... tada ... new box with all the shiny bits. A standard rebuild will be more than $3K. Oh ... and you still have a stupid plastic radiator.

Hope this helps.

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Edited by twisty
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  • 2 weeks later...

If you have you tranny rebuilt, ensure you have the radiator serviced.

Guy at work had two trannys fail before they reliased that the radiator had a intermittant blockages that resulted in the tranny cooking. He was lucky as he had taken the truck in to a tranny repair in bendigo and told them to fix it - they didnt check on the radator oor arranged for him to have it serviced- they reparied the trannys under warranty.

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Good article. I had a look at my cooler and it's completely different to that in your photo. It's at least three times taller and around the same width. Nissan must have done a lot of changes when they designed the CRD, as so many things are different.

Cheers

Ray

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