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Differential Gear Swapping


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Does anyone know if the ring & pinion in an R180 are universal to all r180s? I've dug around but don't see this specific topic covered anywhere; not in this forum, not in the internet generally.

What I mean is, can you use the gears from a Nissan r180 in a Subaru r180 and vice versa? I know that the case inside the differential housing often has model specific attributes, which is why you need the special half-shaft adapters to use a Subaru differential in a Z car, but are the ring and pinion gears universal from one to the next?

Even more specifically, are the pinions all the same throughout these differentials and the ring (or crown) gear is what is changing the gear ratio? Is the bolt pattern on every ring gear for an r180 the same?

The reason I am wondering is I want to understand if you can just go get the ring gear from any r180 that has the number of teeth you want and bolt it into your differential. That would make life a LOT easier when it comes to getting the ideal final drive for your needs.

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16 hours ago, Matthew Abate said:

get the ring gear from any r180 that has the number of teeth you want and bolt it into your differential.

Never had a subaru, so don't know.. i only can say that if you want another ratio or gear, you always have to change 2 ! gears.. not 1.. 

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I understand that the gears come as a set and that the gear teeth have their own face profiles from one manufacturer to the next, but what I’m really looking to know is if r180 is a standard of some sort that allows for interchangeability. Can one put a gear set for a WRX on a Nissan or vice versa. There are many more intermediate ratios available to us if so.

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Maybe you can find out if the manufacturer for nissan is the same for subaru (and many more car brands..) i really don't know. Offcourse that's no guarantee that it will fit. Why not change to a complete R180 from a subaru? (With LSD) Just gears are very difficult to find i think..

(Also: I would be very careful with LSD type diff's because most will/can be wornout..)

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On 9/19/2022 at 11:11 AM, Matthew Abate said:

Does anyone know if the ring & pinion in an R180 are universal to all r180s? I've dug around but don't see this specific topic covered anywhere; not in this forum, not in the internet generally.

What I mean is, can you use the gears from a Nissan r180 in a Subaru r180 and vice versa? I know that the case inside the differential housing often has model specific attributes, which is why you need the special half-shaft adapters to use a Subaru differential in a Z car, but are the ring and pinion gears universal from one to the next?

Even more specifically, are the pinions all the same throughout these differentials and the ring (or crown) gear is what is changing the gear ratio? Is the bolt pattern on every ring gear for an r180 the same?

The reason I am wondering is I want to understand if you can just go get the ring gear from any r180 that has the number of teeth you want and bolt it into your differential. That would make life a LOT easier when it comes to getting the ideal final drive for your needs.

You won’t be able to change gear ratios by simply changing the ring gear only. The ring and pinion gears are always matched. It doesn’t matter what make or brand of differential. A gear set is machined to work together as a set. 
 

So if you have a 4:11 gear set, and a 3:90 gear set, the ring gear from one will not mesh with the pinion on the other. 
 

If you want to change gear ratios, the ring and pinion both have to change.

 

Will a ring and pinion from a Subaru R180 fit in a Datsun R180 case?

Maybe.

But why take them out of a case and put them in another? It takes special tools to set up the pinion bearing preload, as well as training and skills rebuilding differentials, getting the bearings set and the gear wipe pattern correct.

If you want an R180 with a given ratio, buy it and swap the whole unit out.

 

Edited by Racer X
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Because I have access to parts as well as technicians, and one does not learn without trying.

in other news, I stumbled upon this list of part numbers for ring & pinion gears, which I have not yet verified:

38100-U3000.... 3.364
38100-U3100.... 3.545
38100-U3200.... 3.70
38100-U3300.... 3.889
38100-U3400.... 4.11.... used on front of '83- 720 and rears of CA20E S12s.
38100-U3500.... 4.375
38100-U3600.... 4.625

Edited by Matthew Abate
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8 hours ago, Matthew Abate said:

Because I have access to parts as well as technicians

Very good reason then but, it raises also the question: do those technicians not know if that what you want to do is possible?

 

8 hours ago, Matthew Abate said:

and one does not learn without trying.

RIGHT !!   I've learned A LOT by trail and error, as many here will have..  i think..😉

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Not here to debate whether or not someone should do these things. I’m here to understand IF it can be done because this information is not findable on the internet and there is a lot of bad info out there.

For example, I didn’t know that the R in r180 stands for “Rear,” that there is an f180 that was used as the front differential in trucks, and that f180 gears are cut in the opposite direction, meaning you can’t use an f180 as an r180.

I also didn’t know that the ring gear inside diameter changed from 110mm to 115mm at some point in the evolution of the r180 family. Pinning down when that happened would be worthwhile, as would when they switched from 100mm bolts to 12mm bolts and finding out if 9-bolt rings are standard or if there are others.

I would also like to know if any manufacturers other than Subaru and Nissan used r180 differentials with the same case, as that would open up parts availability and swapping potential.

While I appreciate that the complexity of messing with a differential may or may not necessitate caution, wether or not one use the full assembly or chooses to fine tune their differential with internal parts is up to them.

Part numbers, years, models, measurements, and side by side comparisons would be very useful.

 

(edit: the first question these technicians asked when I asked about putting 240z R&P in a Subaru r180 was what I asked in my first post. They are not parts experts across manufacturers, but people working in Subaru service stations. They know how to do it but know whether parts will swap.)

Edited by Matthew Abate
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Here is a comprehensive write up on the R160 through the R200 differentials:

https://www.diyauto.com/manufacturers/nissan/generations/240z/diys/differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount-faq-by-jmortensen

Interesting to note that the Rxxx refers to the diameter of the ring gear, I.e. an R180 has a 180mm ring gear, the R200 has a 200mm ring gear.

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That answered the question! Thanks @Racer X

“Early R180's measure 110mm inside the ring gear. 77 and later model year R180s measure 115mm inside the ring gear. This minor change means that the ring and pinions won't swap between the early and later models. If you have an early diff you must use an early carrier, and if you have the later diff you must use a later carrier. It is possible to use a early carrier on a later ring gear with a spacer…”

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