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Questions about diffs

yoshiii335
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yoshiii335 Rising Star

yoshiii335

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Hello

I found this info someone put up about different Nissan diffs.

Is this correct? http://www.nissansilvia.com/forums/index.php?showtopic=337751

I have learned from other places that having a 4.3 or 4.1 ratio diff is good to get for a rwd turbo car.  Is this a good ratio to have?

 

Edited by yoshiii335
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KiwiRS4T Grand Master

KiwiRS4T

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Posted

Have you got an R32 RB20DE? If so you will have a 4.1 diff already (4.111 non abs or 4.083 if you have abs.

There is no such thing as a good ratio. There is only fit for purpose. What do you want to do that you can't already?

yoshiii335 Rising Star

yoshiii335

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2 hours ago, KiwiRS4T said:

Have you got an R32 RB20DE? If so you will have a 4.1 diff already (4.111 non abs or 4.083 if you have abs.

There is no such thing as a good ratio. There is only fit for purpose. What do you want to do that you can't already?

No, just checking.   Learned that 4.3 is good followed by 4.1 and some people put 4.1 on their turbo cars.

If the diff ratio I have is good already, than I want change.

 

 

Piggaz Grand Master

Piggaz

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Posted

That really doesn't answer the question mate.

You've obviously sat down and thought about the potential gains of a diff ratio change. What are you hoping to gain?

For what's it's worth, put a RB25 NEO in it and enjoy life.

yoshiii335 Rising Star

yoshiii335

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2 minutes ago, Piggaz said:

That really doesn't answer the question mate.

You've obviously sat down and thought about the potential gains of a diff ratio change. What are you hoping to gain?

For what's it's worth, put a RB25 NEO in it and enjoy life.

What I learned is that cars with a 4.3 or 4.1 diffs are good. I learned that sometimes non turbo cars have those diff ratios to help it along.

I learned that 4.3 or 4.1 diffs are good to have in turbo cars.

 

I wasnt sure what mine is.   I am putting a Nismo LSD in mine.   I know my car is over 25 years old and the diff is most likely not working  correctly so I will put in the Nismo.

I change the diff oil once a year to help keep the diff working as well as it can.

GTSBoy Grand Master

GTSBoy

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Posted
17 minutes ago, yoshiii335 said:

What I learned is that cars with a 4.3 or 4.1 diffs are good. I learned that sometimes non turbo cars have those diff ratios to help it along.

I learned that 4.3 or 4.1 diffs are good to have in turbo cars.

 

 

Well......what you learnt is not true.

For drag racing, sure, go for a short diff ratio.  But turbos really like tall diff ratios so you can load the engine up in each gear and get a bigger run in each gear.

My R32 had the obligatory 4.3 diff in it.  When I did the RB25 transplant I put a 4.11 into it, and if I could have found a good way to do a 3.9 I would have.  3.7 was an option but would perhaps be a bit too tall.

 

And your diff oil does not need to be changed every year.  And you especially do not need to be putting LSD compatible oil in it (just in case you are) because your stock diff will be a viscous piece of poo and does not work like a normal LSD.

yoshiii335 Rising Star

yoshiii335

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26 minutes ago, Piggaz said:

That really doesn't answer the question mate.

You've obviously sat down and thought about the potential gains of a diff ratio change. What are you hoping to gain?

For what's it's worth, put a RB25 NEO in it and enjoy life.

I want to have everything to help me with my acceleration as much as possible, non engine parts.

 

2 minutes ago, GTSBoy said:

 

Well......what you learnt is not true.

For drag racing, sure, go for a short diff ratio.  But turbos really like tall diff ratios so you can load the engine up in each gear and get a bigger run in each gear.

My R32 had the obligatory 4.3 diff in it.  When I did the RB25 transplant I put a 4.11 into it, and if I could have found a good way to do a 3.9 I would have.  3.7 was an option but would perhaps be a bit too tall.

 

And your diff oil does not need to be changed every year.  And you especially do not need to be putting LSD compatible oil in it (just in case you are) because your stock diff will be a viscous piece of poo and does not work like a normal LSD.

Ok, little confused, you said what I learned was wrong, but you mentioned that 4.1 is what you had and you wanted to go 3.9.  Yes I understand that 3.9, etc is good.  I wasnt saying that the shorter gears are better. Just what I learned about 4.3 and 4.1.   

So you didnt like your 4.3?   Would it be worth it to put in a 4.1?  My engine later I am looking at is going to be a 25 or 26.  Why couldnt you do a 3.9?

GTSBoy Grand Master

GTSBoy

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Posted
2 hours ago, yoshiii335 said:

So you didnt like your 4.3?   Would it be worth it to put in a 4.1?  My engine later I am looking at is going to be a 25 or 26.  Why couldnt you do a 3.9?

 

4.3 is really short.  For a pissy little engine like an RB20 that's good.  For a bigger, torquier engine like an RB25, higher gears are better.  Hence going to the 4.11 that the R33/4s had.  There wasn't a readily available 3.9 gearset available when I was building my Frankendiff, so I just used the 4.11s.

I'm sure the RB25 would pull 3.7s.  It's doing nearly 3000rpm on the highway in 5th, it could certainly use longer legs.

yoshiii335 Rising Star

yoshiii335

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19 minutes ago, GTSBoy said:

 

4.3 is really short.  For a pissy little engine like an RB20 that's good.  For a bigger, torquier engine like an RB25, higher gears are better.  Hence going to the 4.11 that the R33/4s had.  There wasn't a readily available 3.9 gearset available when I was building my Frankendiff, so I just used the 4.11s.

I'm sure the RB25 would pull 3.7s.  It's doing nearly 3000rpm on the highway in 5th, it could certainly use longer legs.

Is it a pain to change to a 33/34 diff? Many things have to change?

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