92 Full Float Rear Axle Swap Sanity Check (1 Viewer)

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Jan 17, 2019
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Hey guys,

My '92 FJ80 is currently in the shop getting a FF rear along with other goodies. I thought I had researched it enough before dropping it off, but I thought of a couple of possible issues I'd like to be reassured on.

First is the rear drive shaft. From my research, I thought the shorter FJ80 drive shaft did not need to be changed (bolt in as its called). Is this correct? This thread has CDan saying I do need the longer shaft.

Second is the master cylinder. The fronts are being upgraded to FZJ brakes, and the FF has discs as well. Do I need to change the brake master cylinder? My understanding was that the higher pressure the drums required would not adversly affect a disc/disc system. This thread has cruiseroutfit saying I need the disc/disc MC.

I know about the parking brake cable and the 16 inch rims.
 
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Magna, UT
Your factory rear driveshaft will be fine. The different lengths are for different transfer cases, so as long as you're keeping the same Tcase you can keep the same driveshaft.

I would trust @cruiseroutfit recommending a master cylinder replacement to match your new axles.
 
Joined
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Messages
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Southwest
Your factory rear driveshaft will be fine. The different lengths are for different transfer cases, so as long as you're keeping the same Tcase you can keep the same driveshaft.
Thank you for resolving that.

You will want to replace the master cylinder and lspv.
Why the LSPV as well? Is there a difference between an FJ80 and FZJ80 LSPV? And wouldn't it be possible to use the LSPV to compensate for the disc/drum master cylinder?

Not trying to be stubborn, I would like to understand this at depth.
 
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Thank you for resolving that.


Why the LSPV as well? Is there a difference between an FJ80 and FZJ80 LSPV? And wouldn't it be possible to use the LSPV to compensate for the disc/drum master cylinder?

Not trying to be stubborn, I would like to understand this at depth.
It's been some time since I've researched it but I believe disc n drum lspv are different part numbers. It may be the disc lspv ramps up/down pressure at different rates.
 

SUMMIT CRUISERS Jr

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Mar 17, 2013
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Norman, OK
 
I swapped a FF axle into my ‘92. I had already done the FZJ front brake upgrade, and I didn’t touch the LSPV. I’ve never heard of them being different so that’s interesting, but the truck stops great and as it should.
 
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Howzit desertcruiser80. I didn’t change my master cylinder, nor did I touch the LSPV. I had a 94 rolled LC that my friends sister drove and I bought the whole truck for $500. I bought it mainly for the stock LC rims and found out later that I could use a lot of parts to swap on my truck. There was not much support at the time of me doing the swap, so I was taking a chance. The swap is pretty straight forward. The lift that I had was Comp 4” in the front and 863J in the rear. All OME coils. Shocks were also OME. Have fun and be safe. Aloha from Washington State

1st: Jack truck up and put BIG jack stands
2nd: Take tires off
3rd: disassemble axle then remove
4th: install axle first then the coils
5th: install brakeline and shocks
6th: bleed brakes
7th: install rims and tires (torque to spec)
8th: remove jack stands
 

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