Starting a new project...Subaru STI Differential swap into my Z

[Hunter260Z]

Please tell us how many RPM's you turning at 40,60,80mph in 4th gear.

[Kurbycar32]

This seems like quite the victory. I think a step-by-step guide with pictures should be created for future would be swappers.

[Zedyone_kenobi]

Well before I wave the flag of victory I want to take her our for a much longer run. I want to see how she does on the long runs and on the track

But right now I am far more worried about the wheel shimmy

[Zedyone_kenobi]

I did not take that many pictures, but a step by step list would go something like this.

Put rear of car on jack stands as high as you can get them.

Remove rear tires

Disconnect half shafts from wheel hub

Disconnect half shafts from differential

Put half shafts on ground with hardware in plastic baggie

Remove Drive shaft bolts and put in plastic baggie

Remove the bolt holding the diff to the diff mount on the diff crossmember

Remove the two nuts that hold the diff to the mustache bar

(NOTE: on some occasions the studs that screw into the diff rear cover will come out with the nuts, in this happens, you will need to support the differential BEFORE removing the studs!)

The diff is now loose and should move around a little

Place jack under the differential to support its weight (IF studs were coming off with the nuts, you will already have this done)

Remove 4 bolts holding the differential cross member to the chassis

(NOTE: the exhaust may need be lowered to do this, so plan accordingly)

With the crossmember out of the way, slowly balance the diff on the jack and lower it down from the car

you will need to move it forward first to clear the mustache bar before it moves down

Place the Diff on a work surface.

Remove the yoke on the front of the differential. You may or may not need a puller to do this job

Remove the output flanges from either side of the differential (just one bolt holds them in)

Using a press or a 5 lb maul, tap or press the studs out of the flanges, you will need these to install into the wolf creek output flanges.

Thoroughly clean off the studs removed from the OEM output flanges with a wire wheel.

Using an arbor press or rubber mallet, press or tap the studs into the wolf creek output flanges

Acquire a R180 STI rear diff.

Clean diff as well as you can

Inspect the side oil seals on the STI diff for tears, or dry rot. IF questionable, replace with new seals (can be bought at SUBARU Parts and Accessories | SubaruParts.com®)

Install the front yoke from the DATSUN diff to the STI DIFF. The splines are the same and it will slide on, or it may need some convincing with an impact. I cannot speak as to how tight to make this yoke, but it should be very tight. There is no way to get a good running torque on the nut as the splines will make it very hard to get it on so any torque number will be masked by the running torque completely. So try to get a feel for how hard it is to turn the STI yoke and tighten until it feels the same.

At this point you should have the front yoke on and now you can install the wolf creek output flanges into the STI diff. You will notice the wolf creek output flanges have a groove in the splines. THis groove is for a clip that is already inside your diff, go ahead shine a light in there and you will see it. THe flanges do not have any bolts that hold them in. The clip does it all (I know kind of creepy, but the the half shaft once installed gives the output flange nowhere to go, so it will be okay)

Using a rubber mallet gently tap the wolf creek output flange into the STI diff. You will feel it go in and engage the clip

Ensure the diff has plugs in the fill and drain holes. I recommend using female style plugs versus male to make draining easier. You can buy the female plugs at MSA.

Fill the diff with 1 bottle (about 1 liter/1quart) of 75w-90 gear of your choice (80w-90 will work too, but check your FSM for temps and recommended weights)

If the studs came out of your Datsun diff cover with the nuts, Now is the time to remove the nuts. You will probably need a vice or a strong helper to hold the stud while you get the nuts off. Clean thoroughly it will make installation easier

Install the studs back onto the STI diff cover.

Remove the OEM diff mount from the Datsun DIFF and Install the OEM diff mount onto the STI diff.

Place the heavy as **** diff on the jack and jack it up into position. Have the diff cross member and hardware, (THAT YOU CLEANED!) ready to go.

carefully and slowly jack up the diff so that the studs are lined up with the mustache bar. Once they are close wiggle the diff so the studs slide into the mustache bar holes. Once you do that, you are in good shape. Hand tighten the nuts.

Now at this point you can install the diff crossmember with the 4 bolts and the diff is in. Do not forget that nut, washer and lock nut that attaches the diff mount to the diff crossmember.

NOTE: IF you are installing an RT mount, you will have had to install it BEFORE you put the DIFF in. To do that you will have to remove the diff strap hardware from the sides of the transmission tunnel. You will also need to trim the bump stop (if you went that route) about 3/4". I will let the user of these directions figure out what kind of mount they want to use with the RT mount, as there are numerous different styles.

Happy motoring!

Edited November 28, 2013 by Zedyone_kenobi

[Zedyone_kenobi]

Just to cap off this thread. I figured out what my wicket shimmy was. The car had sat a while doing this modification, and while it was sitting we had a hard spell of cold weather. When I checked my tire pressures, I only had 18 psi in the front tires. Upon airing them up, my wicked shimmy was gone. Just goes to show you. Before tackle a problem with extensive money and labor, try common sense things first.

[240260280z]

Classic engineer's eye for detail oversight....not to worry. Investigation and scientific method always wins in the end, just the order the way the problems fall out may not be the easiest path.

[Zedyone_kenobi]

Took the Z out on a few drives and I am now convinced I want to do a 5 speed swap. Keeping the rpm lower on long trips and vintage rallies (which is what I really want to do with my Z) would be a nice benefit.

Just need to go find all the 5 speed swap threads to find which one I want to go with. Probably willing to pick one that will just swap in easy versus trying to pick one that is the most performance oriented.

what I know so far is that the 5 speed is still a type B unit. so it should bolt in. I assume that means I can also use the standard 71 transmission mount. Shifter is still questionable. I may have to do some research on that. I think the Type B shifter I am using now should work. Still, the 5 speed is going to be nice.

Anybody have a good reliable source for good 5 speeds.

[er34gtt2000jp]

I got my JDM Type A 5 speed off Craigslist for $250. Just had to source the front half of the drive shaft from a Roadster guy on Ebay and I was in business. Nice thing about the Type A is no modifications needed to shifter hole or console for a 70-71 car and as long as you're running a 3.90 or higher rear it will be quite nice.

All of the L series Z trans will bolt right in using the 71 trans mount but the shifter hits the opening for a type B trans requiring trimming like 3/4" off the forward lip. I wanted to keep mine all factory so i scoured CL to find a JDM 5 speed.

[Zedyone_kenobi]

I am running a Type B 4 speed right now, so I would think the modifications would be absolutely minimal. Just wanted to be sure before I drop a decent bit of coin on a rebuilt 5 speed box.

[240260280z]

Don't forget the 240sx transmission swap. I think some 300zx's have the same unit. I got one from a 200sx turbo.

[Travel'n Man]

No matter what anybody says - once you get the 5 speed - complete a rebuild before putting that bad boy in...............make it easy on yourself...........you'll be glad you did!

[EuroDat]

Don't forget the 240sx transmission swap. I think some 300zx's have the same unit. I got one from a 200sx turbo.

Hi Blue,

Which 71C came in the 200SX turbo?

I know the early 71C (with the 16mm wide gears) came in the 300ZX N/A Z31 and the 240SX S13. The later version, with the 20mm wide gears set and synchro reverse gear, came in the 240SX S14.

Here is a link that shows the differences well. DSC04293JPGThumbnail1jpg id 266482 | Motortopia

Chas