Hey y'all. I just recently received my F&R pumpkins from L8 and realized they did the D1 flange in the rear. I didn't order a D1 flange or a TW upgrade to work with the 4 bolt flange so I'm wondering if its worth it to delay the install to pick up a D1 rotoflex-less driveshaft. I have a 2 inch lift on my truck so it could probably do with upgraded shafts front and rear but I also want to get the new diffs and gears installed so I can start breaking them in before a roadtrip in July. Any thoughts on just swapping the 3 bolt flange from my stock diff into the new one? How difficult is the swap / any gotchas?

 

I'd say, go for the 4 bolt flange and new prop with u joints on both ends and loose the donut.


Changing the rear diff flange ain't too bad of a thing to do.


Remove the rear prop and rubber donut.

Get a Dremel or something with a small cutting disc and cut the 3 bolt flange open to get the centering pin out easier. It can be very tight to get out without cutting some reliefs to the flange. And you wont be needing it anymore so no reason to try getting it out intact.
Red arrow shows the edge between the pin and flange.



There is a M8 thread inside the pin to attach a slidehammer or something to it.
I had my bigger one on hand as I tried to get it out intact.


Under the centering pin is one bolt, remove it and the flange is out.
Sorry, didn't take a pic of this.

I just did this on mine a few weeks ago.

 

Can the 3 bolt flange be reused after cutting it like that?

 

I wouldn't use it.
It's not strong anymore and is out of balance.

I just have no use for it anymore and used the tools to remove it that I had avail. Maybe with induction heating etc, or the right tool, You could get it out intact.

It can also be locked in with loctite.

 

Ah I figured as much. I have a D1 flange already on my new diffs but I want to install the 3 yoke one from my stock diff so I can use my stock driveshaft. Sounds like I'll just order some Tom Woods driveshafts and wait to install. That way I don't have to do the work twice to remove and replace the flanges on the new diff.

 

Oh yeah, sorry, I misread/understood.

Keep the 4 bolt and order up the new prop.
The 4 bolt don't even have the centering pin.

 

Got it! Thanks for the help! Do you think I need to go with a double cardan rear shaft? I only have a 2 inch lift but I may bump it to 3 inch later on.

 

I ended up ordering a driveshaft because it looks like I can't use the 3 bolt flange with the gearset installed. Bummer because I would have placed the order together if I had known. Whoops. For reference if anyone is doing a regear, you'll need to order a 4 bolt flange compatible shaft from Tom Woods or use FRC8387 which is the RRC SWB or D1 rear driveshaft.

 

I've got a write up on this (see my signature), but the easiest way is to run an M8 tap on thru the center of that. Then you can take an M8 bolt (fully threaded) and just run it in. That will push the piece out, no cutting or slide hammer required.

Yes, in my opinion deleting the rotoflex is worth it if for no other reason than ease of repair or maintenance.

 

I'm probably in the minority but I'm a fan of the rotoflex but given your situation I would do as you did just to minimize work and order a new shaft.