Rear end of choice
05-12-18, 04:16 AM
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Rear end of choice
Hello guys I have a 1983 gsl and I just got a dyno tuned for my set up I’m boosting 9 pounds and I made 325 hp to the wheel but my rear end maxxed out at 140 mph I have a stock rear end and want to up grade it but really don’t want that 8 inch ford just want something with some longer gears and something for street thanks ......need a new rear end but a nicer upgrade. What choices do you guys recommend ... thanks
05-13-18, 11:32 AM
#2
Damn, it did start!
Finding a 84/85 GSL rear end would yield you thicker axles. Not sure if it is really a quantifiable upgrade. The 3.9:1 rear gears as about as tall or long as you can reliably find. RWD 626s had a 3.63:1 ratio. I feel this would be a massive undertaking as availability is extremely limited. I'm afraid to ask, but why do you need to travel faster than a theoretical 140mph? I would rather have a lower top end with shorter gears for punchy acceleration.
05-13-18, 11:25 PM
#3
Finding a 84/85 GSL rear end would yield you thicker axles. Not sure if it is really a quantifiable upgrade. The 3.9:1 rear gears as about as tall or long as you can reliably find. RWD 626s had a 3.63:1 ratio. I feel this would be a massive undertaking as availability is extremely limited. I'm afraid to ask, but why do you need to travel faster than a theoretical 140mph? I would rather have a lower top end with shorter gears for punchy acceleration.
Whats wrong with the ford rear? You can swap diff's on the fly. NA Miata's use the same rear IIRC, but I don't know about their gearing.
05-14-18, 01:04 AM
#4
www.AusRotary.com
With an 84-85 bigger rear, the first point of weakness is the centre itself. I have a Guru/Xtreme rotaries torsen centre, which is documented to easily handle well over 400rwhp (~450rwhp on dynojet). A lot of this is due to the inherent strengths of the Torsen design and I imagine OEM torsen swaps (eg from a Miata) will provide a similarly strong centre, provided it is assembled well. During assembly, there are little mods that can be done to strengthenthe stock centre, such as replacing the collapsible pinion spacer with a solid one, see eg this discussion: S3 rx7 diff. Stronger axles? - AusRotary
The next point of weakness is the axles, but the 26 spline axles can still handle a fair bit of power. As to how much power comes down to driving habits and the amount of traction you can get at the tyres. I know of a car that ran 26 splines axles reliably into the 10s. It was only once the switch was made to racing slicks and hard launches and low 10 sec 1/4 mile runs that the axles couldn't cope anymore and he was replacing them regularly. The safe limit for the thicker axles seems to be around 400rwhp - beyond this, you run much greater risk of failure.
The next point of weakness is the axles, but the 26 spline axles can still handle a fair bit of power. As to how much power comes down to driving habits and the amount of traction you can get at the tyres. I know of a car that ran 26 splines axles reliably into the 10s. It was only once the switch was made to racing slicks and hard launches and low 10 sec 1/4 mile runs that the axles couldn't cope anymore and he was replacing them regularly. The safe limit for the thicker axles seems to be around 400rwhp - beyond this, you run much greater risk of failure.
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