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RB30 Series I and II differences, and 4EN71B Auto trannies


LuciferDarklord

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Whats the difference between series 1 and series 2 RB30? How can you tell the difference? I have 2 in my junk pile up the back of my block that I got given for free from wrecks, just wanna see if they are series 1 or 2 and if there is much difference. Does anyone outside of oceania modify the Jatco 4EN71B auto tranny? They are similar to 3N71B but with a overdrive attachment on the output shaft, so in theory you could make a dual range 3 speed gearbox out of one. I know some of the VL Commodore turbo boys use them in high power drag setups. The overdrive allows you to run a real high ratio diff and spool up early with the short first gear ratio resulting from that combo. Redline in overdrive thru the traps. I'm just curious if they are only released in the Aussie GM Holden version of the RB30. The R31 Skyline here also ran an RB30 and 4EN71B combo until '88 I believe, then they swapped over to another auto, RE4 or something? By that stage the VL Commodore had been replaced by the VN with the boat anchor buick 90 degree V6. The 3N and 4EN71B are loosely based on a ford C3 I think? They have lots of torrington bearings where a C3 only has thrust washers

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i had a turbo jatco box built by a guy into the drag racing scene in WA

he is a whizz with C4's and reckons the jatco has similar strength parts available(used a few parts out of a nissan patrol auto,extra clutches,different overdrive setup,etc) ,and as you mentioned,much better bearings

the overdrive is the weak link,doesn't recommend shifting into it on full boost if you want the box to last

he can't figure out why guys bother messing with the trimatics(traumatics as he calls them)in preference to the jatco

if you don't want the overdrive he reckons stick with the jatco 3 speed out of earlier nissans

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Does anyone outside of oceania modify the Jatco 4EN71B auto tranny? They are similar to 3N71B but with a overdrive attachment on the output shaft, so in theory you could make a dual range 3 speed gearbox out of one.

The trans is actualy a 4n71b and the overdrive is fitted to the front of the trans between the bell housing and the "main" trans case!

 

 

OD.jpg

The 4n71b showing the added O/Drive section

 

 

 

 

 

 

trans3.jpg

This is the 3n71b

 

The big HP RB30's use the 3n71b and do a good job, the "4 speed" 4n71b is good for street use, where good fuel mileage is required. as the O/Drive is 0.686 or over 30% rpm reduction if I remember correctly

 

Check out KEAS Trans here http://www.keas.com.au/

 

 

And the 71 series Jatco transmissions look more like a BW35 in my opinion.

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  • 2 years later...

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