Third member ???

[AR15doctor]

I am working on a 77 FJ40. The yahoo that owned it before me put two different ratio third members in it! The front is a 3.70 and the rear is a 4.10. I want to run 3.70's front and rear to bring my cruising rpm's down. My question is will a 3.70 third member from an 85 FJ60 swap into my housing? Are the third members the same front/rear? Thanks

 

[71FJ40]

The 3rd's are the same but IIRC you may need to swap the flange or get an adapter

 

[dgangle]

yes and you will need a new pinion flange. Marlin Crawler as well as other vendors have them. Order and install a new MC HD pinion seal while you are at it.

Changing out the front third is considerably more involved than the rear so you got that and the fact that the 3.73:1's are not very desirable (read cheap $$) to most both going in your favor.

I have done this and think it is one of my top 3 mods right behind disc brakes and a more comfortable/rearward positioned seats. Plus it is a relatively inexpensive mod.

 

[Mace]

Just "swapping" the flange on a crush sleeve Diff is not the best idea in the world..

 

[dgangle]

Does his donor '85 fj60 uses a crush sleeve?

 

[Mace]

yes...

 

[dgangle]

ahhh....never had anything that new, in FJ's at least.

 

[Josie'sLandCruiser]

Hi All:

So what else is necessary "Mace?"

Installing a new crush sleeve and setting the pinion torque when swapping flanges on this era of third members? Or am I missing something??

Thanks for the advice.

Regards,

Alan

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Just "swapping" the flange on a crush sleeve Diff is not the best idea in the world..

 

[Mace]

Hi All:

So what else is necessary "Mace?"

Installing a new crush sleeve and setting the pinion torque when swapping flanges on this era of third members? Or am I missing something??

Thanks for the advice.

Regards,

Alan

----------------------------------------------------------------------

Yep..

 

[Mr. Toad]

Hi All:

So what else is necessary "Mace?"

Installing a new crush sleeve and setting the pinion torque when swapping flanges on this era of third members? Or am I missing something??

Thanks for the advice.

Regards,

Alan

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Yep..

Nahh, don't mess with the crush sleeve or replacing the flange. The '85 should have a big fat meaty round flange if I'm not mistaken. Put your drive shaft flange up to it and mark a new pattern on that big flange. Then drill it out. No worry about the crush sleeve.

 

[AR15doctor]

I read somewhere that the FJ60 uses a double cardon rear shaft which helps with driveline angle after a lift. I have the CCOT 4" HFS lift on orde so maybe I will just grab the rear shaft from the FJ60 at the same time. That way I know I wont have any mismatch issues with the rear flange. Thanks guys!

 

[Mace]

Early FJ60's had a DC front shaft, not rear shaft.

 

[dgangle]

....and they are getting hard to come and approaching $100/ea in my IME.