q45 diff install

[Meoff Jack]

hello everyone

I am planning to do a high horsepower build and am researching how to do a 90-96 q45 diff.

I read that I can do a Q45 diff with a q45 driverside axle and a 300zx TT driverside axle and that I would need a Q45 5 lug swap in order for this to work.

My question is, Can I buy aftermarket 5 lug swap hubs and it will work or DO I HAVE TO BUY Q45 HUBS in order for it to work?

Iv searched a ton.......If anyone knows and you could tell me that would be great

Thanks everyone for your time

[waxdnuggz]

You have to use q45 tt 300zx hubs. The axle diameter on the splines are thicker then stock size. And you have the axles right. Let me ask this why q45? Are you drag racing the car? What motor trans will you use? What kind of power are you looking at? A z32 diff might be all you need. Z32 non turbo. Its the stock 4.08 gear with vlsd

[Meoff Jack]

Im planning an ls1 t56 swap just stock for a while but eventually turbo. I just dont like the tiny gear ratios. I dont like vlsd cuz I drift for extended periods of time (I run welded) and I want more top end as well with the swap.....not just more acceleration as I like to race high speeds. The corvette ratios are 3.73(i think....just off the top of my head but I know its around there) and the camaro's is like 3.4 or 3.2. So I figured with 3.55 I wouldnt be too far off..... but im new to swaps so what do I know.

hmm I havent considered z32.....but if i did I would go with the turbo

However, I have been looking into it and I was never sure if it was possible but then I stumbled onto a post that showed a guy swapping an exterra Ring and Pinion into a q45 diff. I might be wrong but the q45 and 240sx diff housings are Both R200 correct??? Im really hoping I can swap the Ring and Pinion only and not the differential itself into my 240sx diff housing Keeping the 240sx Diff with q45 ring and Pinion.

heres the thread I saw ---SEARCH--- 4.6 HG46 Pathfinder R200A R&P swap into Q45 R200 VLSD

[waxdnuggz]

Q45 diff is r200 but the axles are thicker and splined different if this is going to never see the street and only a track I would stick with stock near stock gearing. I assume youll never see 170+ mph like the 3.55 will allow. A 4.08 stock gear would render 1st gear useless but make your other gears all power gears. Kinda like most cars have that gear usually 3rd that just pulls harder then the rest. A stock size would do that for 3-5th gear 6 would still be streetable to cruise with tho. And a q45 is an lsd....

[waxdnuggz]

Rear gear calclations

1st 2.66:1
2nd 1.78:1
3rd 1.30:1
4th 1.00:1
5th 0.74:1
6th 0.50:1



Used 25in tall tire (18in rim)+2(3.5in sidewall)=25in tire

*all 98-02 fbody t56 6th gears are .500 after market t56 is .620 which i dont think your using.

(S)=stock rear gear 4.08
(Q)=Q45 rear gear ~3.55

80mph (average spirited driving highway cruising rate)

(S)=80mph @ 2193RPM
(Q)=80mph @ 1908RPM


(S)=150mph @ 4113RPM
(Q)=150mph @ 3578RPM


High rev power would seem as if you wanted a higher gear similar to drag racing. There power bands are upper range because thats where they are staying at (like drifting) your staying in the upper rpms in any type of racing. So why would you take mechanical leverage (larger rear gear) away from your motor?

Just some food for thought.

I explained in another post of mine. Rear gear ratios can be thought of as a mountain bike.

The 1st gear is biggest which is alot easier to turn then the 5th speed on the bike.
the 5th speed is alot harder to turn but takes alot less rotations to achieve the higher speed there for leaving more rpms for higher speed. However with a bigger rear gear its easier to turn which means it takes less time to get to said speed.

[Meoff Jack]

wow actually 2193 rpm @ 80 mph doesnt sound bad at all. I would only be using 17s though. I would drive at events but also on the street as well and was also thinking about gas mileage. My 240 gets terrible gas mileage on the highway. On average of city and hwy driving (btw I drive on the highway around 53-58 mph at 2500-3000rpm) i get 17 mpg...... and I though.......ls1??? hell no.

but in light of that i just might keep the 4.08

I would just really really like to get the kind of gas mileage iv heard about from the ls1

But being a street car as well.....would it be a really bad idea to have the 4.08 gears?

[waxdnuggz]

If your getting 17 mpg highway you have a problem a big one. Leaky injectors, low compression, timing is too retarded, fouled plugs, ect. Give your car a tune up including air filter and fuel filter. Do you have a cold air intake. Ive never liked thosr unless its a real one with the bay blockoff plate that keeps the filter from heat soak.

That was just a guess on wheel size if its a little smaller itll be a little higher but not by too much 100 rpms or so.

With a sound ls1 you can expect 18-27/28 mpg depending on mods and driving style stock you can even expect 30/32 highway.

Think about the j30 diff its 3.9ish not much less then stock but not a wimpy 3.55

Keep us updated. Decide whats best for you not best for others