hi am a rebuilding a 85 rx7 with a 13b series 4 turbo engine it will make resonable power with a bridgeport turbo motor running big boost but am worried about the diif and gearbox, i have a nine inch and a earlly hilux diff,and a 8.8 but would like a rough idea what numbers i can push through the diff before destroying it as im not sure withe cog box either whether to run a c4 auto or a celica turbo box or go with the mazda series 4 turbo box, any help much appreciated,

 

i think it depends. people run 10's on the stock diff, but i broke one with the stock engine.



hows that for an answer?

 

It also depends on which stock ring and pinion you have. There's a good thread on Mazspeed right now about 3.90 vs. 3.93 rearends and gear strengths.



http://www.mazspeed.com/forum/thread.php?t...id=44&styleid=1



I'm running the stock '83 GSL ring & pinion in my half-bridge and I haven't fragged it yet... but I am running 800 treadwear tires so it smokes 'em before it gets any real torque on the R&P.

 

This is a really touch and go subject. I think that J9fd3s hit it on the head. People seem to argue about this all the time.



I have heard that hard launches at about 350 will break it. I will let you know.



Z

 

yeah theres a thin and a thick one.



mine was a gsl-se 4.09, i had some wheel hop, and 235,000miles on it

 

I have heard that 84-85 gears are thinner due to noise complaints in the earlier diffs. I was putting 230whp through a stock 85 se diff, it finnally exploded due to a faulty setup. I was also on my 8th set of tires drifting a 1/2 mile oval track. talk about making your *** pucker, doing 80mph sidewalls then loose all power almost nail a wall.



Your best bet if you are going to use the stock gears is have new bearings installed, and have back lash set corretlly. I currently switched to 4.44 and have had no issues so far.

 

for the record 85 is series3 not 2

 

thanks all for your help ,it gives me an insight on what to expect, and which way to lean in the diff, i guess the cog box would be very similar then, thanks again as i thought it was a series2 but yeah is definatellly a 85year model, im just learing more about it as i just purchased it , i also own a rx4 coupe which will be done soon so this one will be a learing curve for it