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Need a taller final drive

K

kcpaz

Member
Joined
May 3, 2016
Need to figure out the easiest way to change the final drive in my 242GT. Just finished an engine swap with a BMW M54B25 mated to a ZF 5 speed which has a 1:1 5th gear ratio. This doesn’t jive well with the 3.91:1 final drive in my 1030 axle. From the research I’ve done, the tallest axle assembly that would simply bolt-in would have a 3.31:1 final drive, which would be a big improvement, but sourcing a complete axle assembly that isn’t rusted to crap, in the state where the car is (SD), will be next to impossible. As an easier, cheaper alternative, is it possible to just buy a standard rotation gear set for a Dana 30 and install that? This R&P from Yukon with its 3.08:1 ratio would be almost a perfect match to what BMW put behind this ZF 5 speed.

DANA 30 CJ/ZJ GEARS

DANA 30 CJ/ZJ RING AND PINIONS GEARS FOR YOUR JEEP
eastcoastgearsupply.com
 
OttoB said:
You need different carrier. The offset is different.
Click to expand...
So will the <3.54 R&P with a matching <3.54 carrier work in the Volvo’s housing correctly?


… now that I’m looking at Eaton’s site, it appears that wouldn’t work because the axle diameter is slightly different? Or maybe it’s just a typo? (1.15” for the Volvo and 1.16” for the Jeep application). 🤨
 
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3.08 might be a little tall if you want performance driving. I had an M50B25/ZF car with 3.15s and it was pleasant for a daily, I know the M52B28 cars were 2.93 or so but the US M3s were 3.23:1.
 
OVERDRIVE said:
3.08 might be a little tall if you want performance driving. I had an M50B25/ZF car with 3.15s and it was pleasant for a daily, I know the M52B28 cars were 2.93 or so but the US M3s were 3.23:1.
Click to expand...
It’s mostly going to just be a daily driver/cruiser. I think a 3.15 would be good too (what the 1995 US M3 came with) but the closest thing I can find for the Dana 30 is a 3.08
 
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mikep said:
Get a 3.31 in an axle from a non-rusty state, and you can upgrade to a 1031.
Click to expand...
I will if I can find one, but at a certain point, time is money, and if I can just buy new parts and install them into my current axle, that will probably be cheaper, plus, have the added benefit of upgrading to an LSD.
 
kcpaz said:
I will if I can find one, but at a certain point, time is money, and if I can just buy new parts and install them into my current axle, that will probably be cheaper, plus, have the added benefit of upgrading to an LSD.
Click to expand...
Time is money if you spend it not making money.
Waiting for the right deal is time well spent.
 
Car-part.com has them in CA for $350-400. Everywhere else $200-300.
It’s odd that 3/4 of the states don’t list them.
Find the semi-local yards and call for an 88-up manual trans axle. Or see if the cali yards will ship. Or take a drive.
 
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