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R180 gear swap?


BadDog

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I'm looking at putting an '83 ZX (NA) 5-speed into my '73. If I could get hold of a 3.7 or 3.9 ring and pinion set for the R180 diff, could I just swap those parts to change the diff ratio, or is it more involved than that? I'm trying to avoid the added expense of an R200 swap to get a 3.9 diff, and/or having an entire diff shipped to me...

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You are correct in your assumption however, I,m not so sure of the availability of those ratios for the R180. I'm quessing that Blake likely knows the answer to that question.......Blake!!!

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An alternative - if the ratio is acceptable - is to use a R180 diff from an automatic 240Z, which I believe has a 3.54 ratio. Shipping a diff isn't that expensive if you do it through Greyhound. You have to pick it up at the bus terminal, but its the cheapest way I know to send something big.

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I'm trying to avoid the added expense of an R200 swap to get a 3.9 diff, and/or having an entire diff shipped to me...
Properly setting up a ring and pinion is fussy work, and takes specialized skills and knowledge. If you lack those skills, paying someone to do that for you will easily cost more than the R200 swap.
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I passed up an 3.9:1 R200 this winter because of the negative comments I read in these threads:

http://www.classiczcars.com/forums/showthread.php?t=24759&highlight=R200

http://www.classiczcars.com/forums/showthread.php?t=28286&highlight=R200

I knew that my R180 3.36:1 is in good shape, and after spending the money to have my half shafts rebuilt I am not interested in anything that might tear them up...

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Thanks guys! exploring my options, basically... I posed this question because I found a few ring and pinion gear sets for sale and one was a 3.7 set for a Maxima R180. But then I found at that the "early" R180 a different internal size than that "later" R180. I checked my '73 FSM but couldn't find that spec :-\ I've seen statements that "early" R180s are up to 76-78 era, but others that say it's only 71 and earlier...

Either way, I have a line on a 4x4 3.9 diff, and an '84 Maxima 3.7 diff. The guy helping me out with the whole swap is an ex-racer who did most of his own work (and he has several R200 3.9's lying around) and he seemed pretty comfortable with the idea of a ring and pinion swap if I could find the parts.

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The guy helping me out with the whole swap is an ex-racer who did most of his own work (and he has several R200 3.9's lying around) and he seemed pretty comfortable with the idea of a ring and pinion swap if I could find the parts.

That may be the exception to the rule, but the general rule is that it is far easier to swap in a diff that already has the correct ratio than to install a ring and pinion. The FSM shows special tools and complicated procedures for setting pinion depth.

As with any diff it can be done just by looking at the wipe pattern of the gears, but adjusting things will require shims that probably aren't on the shelf of your local dealer. It may be possible to use shims from a different vehicle, but it does take some skill to get things set up correctly so that the diff doesn't whine. This gear installation manual has some pretty good wipe pattern do's and dont's at the end and may be helpful: http://www.ringpinion.com/Content/HowTo/TechnicalInstructions/Yukon_Installation_Kit.pdf

I'd suggest the 3.9 diff, or a 4.11. I was autocrossing and daily driving my Z for years with the ZX trans and 3.7 diff, and I felt that the 3.7 was a bit tall when I ran that combination.

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I'd suggest the 3.9 diff, or a 4.11. I was autocrossing and daily driving my Z for years with the ZX trans and 3.7 diff, and I felt that the 3.7 was a bit tall when I ran that combination.

Really? I was thinking 3.7 would be a good compromise for highway cruising where I (have to) do a lot of my daily Z driving, yet still not be a dog off the line like the original 3.3x or even the automatic 3.5x might be...

Thanks for the other info too, I had come across ringpinion.com before in my research but hadn't checked out that .pdf yet :)

The ideal situation for me would be to get a used R180 with the desired gear set, as that would require fewer "donor" parts and save some weight over an R200 for my poor L24 to lug around ;-)

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I used to sell parts for Randy's and have been through that .pdf booklet many many times.

I've driven the 3.36 with ZX trans and it is painfully slow off the line and 5th is useless for anything but flat ground in my opinion. The 3.7 is better for sure, but a 3.9 is what was used from the factory on the ZXs with the 5 speeds and a 4.11 would be a small step up from there.

Have you used the transmission calculator? You can input your tire size and figure out your revs at a given speed. Might help your decision: http://www.geocities.com/z_design_studio/

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If you use a newer R180 the axles don't bolt in. There are several workarounds for that. You can buy modified stubs from www.betamotorsports.com or you can disassemble the carrier and install the threaded "button" that the stub axles bolt to. Obviously the modified stubs is the easier way to go, but the other really isn't difficult and I'm sure your racer friend could do that with his eyes closed. More details on that procedure here (where the pictures start): http://forums.hybridz.org/showthread.php?t=114798

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I used to sell parts for Randy's and have been through that .pdf booklet many many times.

I've driven the 3.36 with ZX trans and it is painfully slow off the line and 5th is useless for anything but flat ground in my opinion. The 3.7 is better for sure, but a 3.9 is what was used from the factory on the ZXs with the 5 speeds and a 4.11 would be a small step up from there.

Have you used the transmission calculator? You can input your tire size and figure out your revs at a given speed. Might help your decision: http://www.geocities.com/z_design_studio/

Yeah, my friend was saying his car has the 3.9 and gets a little buzzy on long highway drives - but then again, I've put sound deadening in my car. And yes, I've used that calculator, its great! Funny thing is, even with a 4.11, my car would still be turning 300 fewer revs than it does now at 75 mph with that '83 tranny. A 3.9 would knock it down to 2974, which would save a lot of gas on the highway for me - I like to drive ~75, but tend to keep my Z under 70 i.e. around 3000 RPM or else gas milage drops way down.

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