4.083 Advice
03-10-2017, 07:57 AM
#1
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4.083 Advice
Sometime in the next 4 to 6 weeks, I'll be having my mechanic swap out the original rear diff gear & pinion for 4.083 gears. I've been planning on this for a number of years now, and finally this is the mod I've scheduled for 2017. It's coming. 
Anyway, he's asked that I find if there are any common tips or specific advice for the install. He's been a street/pro mechanic for 20 years, and I've been going to him for the last 10. I've a great deal of faith in this guy, he's honest and fair, and he has no qualms about doing this job. However, he's not done a rear gear swap on this particular car before, so it was a prudent ask, and could only help.
So... anyone?
As part of this work, he'll also be swapping in Whiteline rear diff bushings. That's a pretty straight-forward project for him, but if you've specific shop advice here, I'd welcome that too.
Thanks, gearheads!
Anyway, he's asked that I find if there are any common tips or specific advice for the install. He's been a street/pro mechanic for 20 years, and I've been going to him for the last 10. I've a great deal of faith in this guy, he's honest and fair, and he has no qualms about doing this job. However, he's not done a rear gear swap on this particular car before, so it was a prudent ask, and could only help.
So... anyone?
As part of this work, he'll also be swapping in Whiteline rear diff bushings. That's a pretty straight-forward project for him, but if you've specific shop advice here, I'd welcome that too.
Thanks, gearheads!
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socketz67 (03-14-2017)
03-10-2017, 08:56 AM
#2
There are a couple different ways the one bushing can be assembled that affects sound/vibration.
Update:
I just got back from Fast Intentions (New Exhaust), took a 35 mile drive. With the window open!!!!!
Exhaust sounded great, something was not feeling just right.
There was a phasing feel/sound in the car.
Further investigation, revealed the exhaust pulses were out of sync against a driveline vibration.
I never felt that before!!!
Long story short:
I decided to alter the position of my differential bushings, with and without the "top hat" washer.
Bottom line:
I ended up with the thicker bushing on top, thin bushing on bottom using the large washer, with no top hat washer above the top bushing.
With the old exhaust, I though I just had a little NVH.
I just got back from Fast Intentions (New Exhaust), took a 35 mile drive. With the window open!!!!!
Exhaust sounded great, something was not feeling just right.
There was a phasing feel/sound in the car.
Further investigation, revealed the exhaust pulses were out of sync against a driveline vibration.
I never felt that before!!!
Long story short:
I decided to alter the position of my differential bushings, with and without the "top hat" washer.
Bottom line:
I ended up with the thicker bushing on top, thin bushing on bottom using the large washer, with no top hat washer above the top bushing.
With the old exhaust, I though I just had a little NVH.
From this thread: https://www.myg37.com/forums/d-i-y-i...ushings-6.html
Whatever way mine was put on definitely increased sound/vibration, but I have a relatively quite exhaust, so it isn't bothersome.
IDK the "right" way for your setup, but be advised.
Good luck
03-10-2017, 09:51 AM
#3
Has your mechanic assembled differentials before?
There is a specific procedure to make sure the pinion is not too close or too far to the ring gear. https://www.ringpinion.com/Content/B...h-Patterns.pdf
Have you thought about buying a used diff and swap in the gears? Then you can easily go back to stock and sell the modded diff just incase you don't like shifting more often, noise, fuel economy or anything else.
Anyways, I look forward to your review.
There is a specific procedure to make sure the pinion is not too close or too far to the ring gear. https://www.ringpinion.com/Content/B...h-Patterns.pdf
Have you thought about buying a used diff and swap in the gears? Then you can easily go back to stock and sell the modded diff just incase you don't like shifting more often, noise, fuel economy or anything else.
Anyways, I look forward to your review.
03-10-2017, 10:16 AM
#4
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Has your mechanic assembled differentials before?
There is a specific procedure to make sure the pinion is not too close or too far to the ring gear. https://www.ringpinion.com/Content/B...h-Patterns.pdf
Have you thought about buying a used diff and swap in the gears? Then you can easily go back to stock and sell the modded diff just incase you don't like shifting more often, noise, fuel economy or anything else.
Anyways, I look forward to your review.
There is a specific procedure to make sure the pinion is not too close or too far to the ring gear. https://www.ringpinion.com/Content/B...h-Patterns.pdf
Have you thought about buying a used diff and swap in the gears? Then you can easily go back to stock and sell the modded diff just incase you don't like shifting more often, noise, fuel economy or anything else.
Anyways, I look forward to your review.
Thanks for the link... reading now.
Not buying a used diff for this project. Like many mods, it's a leap of faith based on research and planning.
NVH is already ever-present because of the exhaust, intake, and particularly because of the transmission mount. Not worried about that.
Mileage issues are a highway thing, and I only drive the car less than 5k miles per year, so not worried about that either.
Constant shifting is a joy... because of the short-throw shifter and the RJM pedal, so that's not a concern either.
03-11-2017, 05:49 AM
#6
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Say, is it best practice to flush & fill gear oil again after the swap? Do you know what the reccomendation is for this? That question has been floating around in my head for a while.
Last edited by Rochester; 03-11-2017 at 07:19 AM.
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Rochester (03-23-2017)
04-10-2017, 12:23 PM
#9
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Stopped by to talk with my mechanic this morning, to get on his schedule for the gear swap. We're tentatively planning on next week. So... 10 days.
IIRC, these gears originated on the Nissan Frontier, right? My mechanic asked if the differential housing is the same on the Frontier as the one in my car. Anybody know the answer to that?
IIRC, these gears originated on the Nissan Frontier, right? My mechanic asked if the differential housing is the same on the Frontier as the one in my car. Anybody know the answer to that?
Last edited by Rochester; 04-10-2017 at 02:47 PM.
05-07-2017, 10:06 AM
#10
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Diff bushings are installed. New gear & pinion are installed, along with all the bearings and bushings in the rebuild kit. All told, it was a 10 hour job, of which the main diff bushing chewed up many hours. Very messy job. The diff work went off without a hitch, although it's certainly a project needing skills, experience, proper shop & tools, and patience.
End result? Holy crap, my low end has come alive! There is so much torque rowing from 1st to 2nd to 3rd... it's kind of breathtaking. And yet, throughout it all, the car is totally driveable. In fact, there's a good argument to be made why the car is actually more driveable than before.
Amazing mod. So freaking happy. Here's the thread:
https://www.myg37.com/forums/g37-sed...6mt-sedan.html
End result? Holy crap, my low end has come alive! There is so much torque rowing from 1st to 2nd to 3rd... it's kind of breathtaking. And yet, throughout it all, the car is totally driveable. In fact, there's a good argument to be made why the car is actually more driveable than before.
Amazing mod. So freaking happy.
Here's the thread:https://www.myg37.com/forums/g37-sed...6mt-sedan.html
Last edited by Rochester; 06-02-2017 at 07:29 PM.
05-07-2017, 03:52 PM
#11
I know they are very similar. The standard frontier rearend (C200) is likely just a solid version of the IRS diff (R200) in our cars. I'm almost certain I've read that the ring gears freely swap between them.
