Q45 REAR END SWAPS

[djessyjames]

STOCK GEARS FOR A Q45 ARE 3.538 FROM 90-96 STOCK GEARS FOR A 90-96 300ZX ARE 4.083 NON TURBO ONLY, IF YOU HAVE A Q45 MAKE THE SWAP IF YOU ALOT MORE LOW END TO MID RANGE POWER, MY STOCK Q DID THE QUARTER IN 15 FLAT WITH 93 OCT. 14.2 WITH A 4 INCH CAI PIPE NO CONVERTERS AND TRUE DUALS, 89MPH ON THE STOCK RUN AND 96 MPH ON THE SECOND, ILL HIT THE TRACK IN 3.5 WEEKS TO SEE WHAT THE NEW TIMES ARE,

[240crawler]

I would like the higher gears in my 91 240. Will the Q45 gears fit in my case, or do I have to change rears?

[nismofly]

you can run the rear end from an r32 skyline gts to get 4.36 ratio

the 240 comes stock with 4.08

[elwesso]

He wants to run the higher (lower numerically) gears in his 240...

From what I hear you can do it, however youll have to either put the different flanges on it (the 3 groups of 2 instead of 6 evenly spaced) or use the Q45 halfshafts and diff... in which case you may have to switch to Q45 wheel bearings...

I dont know how easy it is, but its certainly a lot easier to go with the j30 diff for 240 guys.

To the original poster- how did you get the 300ZX diff into your Q?

[nismofly]

wes is the Q an r200 or r230 diff?

if hes talking longer gears, the j30 has a 3.91, the s15 came with 3.69

[elwesso]

the FSM says its an R200 but i think its an R230 since the R200 (300ZX N/A) diff will not fit in the Q45 case as it is not big enough, and spacers are needed.....

The 300ZX TT and Q45 diff are almost identical, minus the companion flange. The Q has a regular 4 bolt companion flange, whereas the Z32 has that goofy coupling thing.

[240crawler]

I am also wondering if I can buy an aftermarket gearset for the 240. I would like between a 3.08 and a 3.42 for my car. Most of my driving is at higher speeds, so the cruise RPM will be lower, and I can hold each gear longer to take advantage of the engine's torque.

[nismofly]

your car will accelerate painfully slow and the difference will be minimal

were talking a few hundred rpm's lower and another 5 or 6 mph at the top of each gear

theres nothing that low available unless you did something quite custom anyway

lowest you can just swap is the s15, which is 3.69

[240crawler]

your car will accelerate painfully slow and the difference will be minimalwere talking a few hundred rpm's lower and another 5 or 6 mph at the top of each gear

Car will not be that slow, I love high gears. Plus, If I have a 4.08 and change to a 3.08, that is a 25% increase in ground speed at any give RPM. I changed my factory 3.7 to a 4.56 in my Stang, and I cried. Yes the pull was good for 1/8 mile strip, but cruise and highway were the suck. In 5th gear, the corrected ground speed was only 125 at 5700. Compare to about 150 at 4500. That was power and drag limited, of course.

lowest you can just swap is the s15, which is 3.69

How do I get a s15 rear, and what is the cost?

[nismofly]

well it already runs around 16 flat...so youd just be making it that much slower

i guess if youre just looking for lower highway rpms it wont matter though

also, using that speed calculating method, if your mustang did 150 at 4500 before, it would be at 121 at 4500 after, and youre saying it was at 125 at 5700, thats 1200 rpms for 4 mph...

anyway, if you want though, you have to source the rear end, ebay or something of that nature would be your best bet...i dont know of any shops that sell it

[hannibal]

Many of the engine/front clip importers can get the rear end for you. Or check the classifieds and Ebay. The diff is a helical LSD and I'm guessing about $500-600 for the whole diff.