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GU III 4.8L Manual to Auto conversion.

Posted: Mon Dec 14, 2009 8:53 pm
by Mav Middy Chev
Hey guys, Just wondering if anyones done this before, and can they fill in some blanks for me.
I own a 2002 GU III 4.8l manual wagon. I want to put a factory GU auto in it.
Do I need to buy an auto out of another 4.8 petty or will another suffice? Im guessing different engines have different bell housings, Fly wheels etc.
What issues will I encounter with the computer, I understand that the one ECU controls engine and auto, Not like the old GQ which had a seperate computer just for the auto. This being the case, I get an auto ECU but does my wiring loom have the auto gearbox loom in it, or do I need to aquire/Make the extra loom for the auto ?
Does anyone know what the final drive is out of the auto compared to the manual? My manual has 4.3 diff gears and just wondered if im gunna have to look at changing them too.
Any advice would be greatly appreciated.

TB48 Auto Conversion

Posted: Wed Dec 16, 2009 7:56 am
by mooseboost
Hi Mate,

Nissan TB48 Auto's run 3.5 diff ratio standard. If you running 35" 4.3's work fine as with have a customer that we changed his diff ratios to this. You would need an auto loom and computer. You would really want to buy a complete conversion set-up of a wreckers so you get every thing you need. Check your rear diff and make sure it isn't the big diff. If it is you can't get different diff ratios. The bigger diff in a Nissan has bolts holding the center in, not studs and nuts like the smaller diffs. It will look different to the front front diff center if it is the bigger diff. Hope this helps.

Posted: Wed Dec 16, 2009 8:11 am
by weeman
like moose said check the size of your rear diff if its a big rear diff you will need to purchase a small diff to change your ratios.

However 4.3 in gu auto you will be able to use more 37 not 35 as if you leave the 4.3 and 35's it will rev to hard and if you have anything small like 33's or 31 will be reving way to hard.

my mate in is gu ute with a 4.8 and auto runs 4.1 ratios and turns 37's however 4.3 will bring his gearing back to perfect...

however in my opinion you may just be better to sell and purchase again as there are generally more autos than manuals forsale

Posted: Wed Dec 16, 2009 5:48 pm
by AFeral
The tb 48 and auto run a bus system, so you will need the engine ecu, gear box controller computer, dash and maybe the ignition key and barrel. All of these bit talk to each other so if one is missing,no go. I came to the conclution it was easyer to manualise the auto gearbox and run after market computer.
Some good info here
www.outerlimits4x4.com/ftopic188867.php&highlight=tb48

Posted: Sun Dec 20, 2009 12:52 pm
by Mav Middy Chev
Thanks Guys, Yeah I do have the big rear diff. And Ive just down graded from 7" lift and 35's to 33's and a 3" lift Cos im making it the wifes family wagon. Thats the reasoning for the auto.
It might be more work than I have thought of, Might be best to strip all my other gear off, Sell it and buy an auto.............. Or just make her drive a manual !
Thanks for your info guys.