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2017 to 2009 6MT Diff Swap - Install Notes

I've been living with a bad side bearing on my diff for about a year now. Mileage is now about 95k. Since used diffs go for about $500-600 for a

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Old 08-27-2018, 02:03 PM   #1 (permalink)
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Default 2017 to 2009 6MT Diff Swap - Install Notes

I've been living with a bad side bearing on my diff for about a year now. Mileage is now about 95k. Since used diffs go for about $500-600 for a 40k unit I decided I would let it ride and just replace the whole pumpkin. Ended up getting a 5k 2017 unit for $900 shipped. More than I wanted to spend but for being essentially brand new it seemed like a good way to go.

Since I had already pulled my diff for mount bushing replacement before, all the bolts were pretty easy and the job was quick - not the case the first time I pulled it. That **** is torqued down tight!

Everything was smooth until I realized the output shafts (stub shafts) changed in 2011. They flipped the threads from the drive shafts to the output shafts. Had to pull the unit again and swap the output shafts from my old unit. A note on the swap: The short shaft is retained by a circlip. Removal required a deadblow with a sledge and a large wood block. Long shaft did not have a retainer and was easier with just a carefully placed pry bar to free up. Another note on the sensor wires: They changed at some point, don't know the year. They now use different sized plugs left to right so that they can't be cross plugged. Swapped for my old ones and all was well.

Result of the swap was definitely good. The bearing hum/roar is gone and the clunky slop from the diff is gone. (FYI, I replaced the wheel bearings on this car because I suspected that over a diff side bearing. Very hard to tell apart since I have the urethane diff mounts.) However, I still have slack in the driveline. I plan on replacing the short shafts then going after the drive shaft and transmission for issues.

Synchro rev match seems off. Revs are about 200 rpm below a matched shift. I thought all years' manual transmission sport had the 3.69 gears. Maybe they changed ratios in '11 with the other changes?

Tools:
Most bolts are pretty large, I'd suggest:
Spray all bolts with penetrant several hours before
Large 3/8 and 1/2 breaker bar
Sockets and gear wrenches 12, 14, 15 and 17mm (from memory)
Extensions
Sledge and large wood block for output shafts
Jack with strap
Jack stands
Friend for jacking/installing diff

Removal notes:
Order is exhaust pipe rear section, v-shaped chassis brace, sway bar, drive shaft, short shafts (inside only), diff
Wheels can stay on.
Expect to shear off exhaust bolts, grind and drill studs, replace bolts
Muffler can stay in place and can be forced out of the way to remove the exhaust section.
Short shaft bolts need to be loosened with the brake set for half of them, unset brake, spin shaft 180, set brake, remove remaining.
Hang your short shafts with bungees. Don't dangle!
Drive shaft can be supported on the aluminum shield by placing a wrench across it under the shaft.
Drive shaft can be manipulated out of the way when removing the diff - may be easier to fully remove shaft.
Replace your diff mounts while it's off the car!!!! Optional: get a better LSD, change your gear ratio, swap your gear oil.

See the great DIY thread on here about replacing the mounts. Warning: It's a bitch to do the rear mount!

It think that's all the stuff I wish I had known!
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Old 08-27-2018, 07:58 PM   #2 (permalink)
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Why didn't you get different bolts, like I did?

Went from a 2017 to a 2009 pumpkin and just used the bolts required for that model year.
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Old 08-27-2018, 08:17 PM   #3 (permalink)
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I read about the different bolts but I needed to get the car reassembled for the next day. Don't have my second car anymore.

Curious about the bolts though. If both sides are threaded how do the bolts work? The shank on my bolts are larger than the diameter of the threads so the bolt stops short. Do the new bolts have a narrow shank to pass through the first set of threads?

Edit: Actually, if you went backwards in year, the pumpkin would have no threads on the output shafts. Are your short shafts threaded or not? Did you use bolts and nuts like the 350?

Last edited by ecoplunge; 08-27-2018 at 08:20 PM. Reason: Added additional question
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Old 08-27-2018, 08:29 PM   #4 (permalink)
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Both sides are not intended to be threaded.

The early 370 had threads in the drive axle hole and a through hole in the side flange. Bolts are installed from the pumpkin side, which is a PITA. This was reversed in later models, where the side flanges were threaded and the through holes where in the axles. I belive this change was made to improve tooling and reduce assembly cost at the vehicle assembly plant.
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Old 08-27-2018, 08:41 PM   #5 (permalink)
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So following up on my original post about the synchro rev match and gearing. I believe I bought a Nismo diff. It was marked as Nismo but I thought it was an error since it didn't have the finned cover. Was the finned cover removed at some year? Was it always optional?

Pretty sure I'm at 3.91 now based on another thread about revs at 70mph.

Quote:
With the stock gear ratio, you are at 2,600 RPM in 6th gear at 70 MPH.

With the 4.08 ratio you are a hair under 2,900 RPM in 6th gear at 70 MPH.
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Old 08-27-2018, 08:48 PM   #6 (permalink)
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Quote:
Originally Posted by SG4247 View Post
Both sides are not threaded.

The early 370 had threads in the drive axle hole and a through hole in the side flange. Bolts are installed from the pumpkin side, which is a PITA. This was reversed in later models, where the side flanges were threaded and the through holes where in the axles. I belive this change was made to improve tooling and reduce assembly cost at the vehicle assembly plant.
The pic you posted is the original setup on mine (2009). With the swap of the 2017 pumpkin on first install I had threads on the short shafts (original) and threads on the output shafts (new). This obviously wouldn't work as I couldn't torque down the bolts with double threading. So I had to swap the output shafts.
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Old 08-27-2018, 09:44 PM   #7 (permalink)
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Quote:
Originally Posted by ecoplunge View Post
The pic you posted is the original setup on mine (2009). With the swap of the 2017 pumpkin on first install I had threads on the short shafts (original) and threads on the output shafts (new). This obviously wouldn't work as I couldn't torque down the bolts with double threading. So I had to swap the output shafts.
Exactly,, My swap was a 2016 VLSD into a 2010 model. I just had the threads drilled out of the 2016 side flanges by a machine shop to the original diameter as my 2010 diff flanges. Perfect! Bolted right up, as shown in my pic with the original 2010 bolts. Machine shop said they were easy to drill out. I didnt want to harvest the flanges from my 2010 diff since it was low miles, and I didnt want to cannabilize it.

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Old 08-27-2018, 11:38 PM   #8 (permalink)
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Quote:
Originally Posted by ecoplunge View Post
So following up on my original post about the synchro rev match and gearing. I believe I bought a Nismo diff. It was marked as Nismo but I thought it was an error since it didn't have the finned cover. Was the finned cover removed at some year? Was it always optional?

Pretty sure I'm at 3.91 now based on another thread about revs at 70mph.



Nismo's do not come with a finned cover. It's the same cover as on all models. Nissan Motorsports makes a Nismo cover that is finned. You have to install it yourself. The newer Nismo's come with lower gears now.
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Old 08-28-2018, 11:22 AM   #9 (permalink)
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Quote:
Originally Posted by Rusty View Post
Nismo's do not come with a finned cover. It's the same cover as on all models. Nissan Motorsports makes a Nismo cover that is finned. You have to install it yourself. The newer Nismo's come with lower gears now.
Excellent info. Didn't realize I had incorrectly thought the cover was factory installed. And thanks for the gearing info too. I had a feeling they changed that for the Nismo at some point but couldn't find anything written. Do you know what year it changed?
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Old 09-02-2018, 12:27 PM   #10 (permalink)
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I can fix the synchro rev error for you by updating the differential specifications using ecutek, pm me if you’re interested in having that issue resolved.
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