78 FJ40 Rear Dif Seals

MudBoy2 · 03-14-2008, 01:37 PM

Hello All,

I have a 1978 FJ40 and noticed that I have a leak in the front (close to the drive shaft u-joint) of my rear differential. I did some research to see what it would take to replace the seal since the gears seem tight and only have 75K original miles on them. I would like to avoid a complete rebuild if possible. From what I can tell, I have to remove the rear dif housing, pull both axles, remove the third member, then replace the front seal and re-assemble. Is this correct? Seems like quite a process to me. I would then have to replace both axle seals and the rear dif cover seal if I'm not mistaken. Does anyone know of any short cuts to this process? Would I be better off having a local transmission shop do the work (rough quote was $100-150)?

Any thought or instruction would be great.

Thanks

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FlyingLow · 03-15-2008, 01:13 AM

Ya, leave all that crap installed and buy a new nut and seal from Toyota. Remove the drive shaft, remove the pinion nut (a bit of a pita, grind the staking out if you need to), and the d/s flange. You may have to put the truck in 4 low with the parking brake on to hold it to break the nut free. Use a screw driver, small prybar or channel lock pliers (my favorite) to remove the old seal. If the pinion falls in a little just push the truck BACKWARDS a little bit and it will push it out. Drive the new seal in and reassemble in reverse order. Make sure there is no grove on the flange where the seal rides, if there is you could either install a speedi sleeve or just don't seat the seal in as far. Leave it out 1/16 or so the seal rides on a different position. MAKE SURE YOU TORQUE AND STAKE THE NEW NUT! If you try to reuse the old nut you won't get true torque. I think torque is 110 ft pounds but get the propper torque from a manual and use the minimum because you probably have a crush sleeve in there that could crush more if you torque more than was originally applied. That would change your gear mesh patern. That is for another thread though. Its pretty simple once you get into it. Good luck and let us know how it goes.

MudBoy2 · 03-17-2008, 01:44 PM

Thanks for th info. Sounds doable. I checked the fluid levels and cleaned off the bottom of the dif just so that I could keep an eye on it until I knew how to fix it. I was surprised to find that the dif was full and now it shows no signs of leaking. Is it possible for the seal to have re-sealed its self?

Thanks again.

FlyingLow · 03-17-2008, 03:42 PM

Sometimes they leak through the splines and when you remove the d/s from the flange a teaspoon will leak out. This is not really fixed with the seal replacement. It will have to leak a lot to change the oil level significantly. A little oil goes a long way when it comes to making a mess though. Won't hurt to clean it up though and monitor it.

03-15-2008, 01:13 AM	#2 (permalink)
FlyingLow Registered User Join Date: Jul 2007 Location: Van Island BC Posts: 93	Ya, leave all that crap installed and buy a new nut and seal from Toyota. Remove the drive shaft, remove the pinion nut (a bit of a pita, grind the staking out if you need to), and the d/s flange. You may have to put the truck in 4 low with the parking brake on to hold it to break the nut free. Use a screw driver, small prybar or channel lock pliers (my favorite) to remove the old seal. If the pinion falls in a little just push the truck BACKWARDS a little bit and it will push it out. Drive the new seal in and reassemble in reverse order. Make sure there is no grove on the flange where the seal rides, if there is you could either install a speedi sleeve or just don't seat the seal in as far. Leave it out 1/16 or so the seal rides on a different position. MAKE SURE YOU TORQUE AND STAKE THE NEW NUT! If you try to reuse the old nut you won't get true torque. I think torque is 110 ft pounds but get the propper torque from a manual and use the minimum because you probably have a crush sleeve in there that could crush more if you torque more than was originally applied. That would change your gear mesh patern. That is for another thread though. Its pretty simple once you get into it. Good luck and let us know how it goes. __________________ 77 FJ40 36 TSLs, 45 springs in rear, 8274, ARB rear, TBI 2F 97 4 Runner Ltd TLCA# 9203 Last edited by FlyingLow; 03-15-2008 at 01:15 AM.

03-17-2008, 01:44 PM	#3 (permalink)
MudBoy2 Registered User Join Date: Mar 2008 Posts: 8	Thanks for th info. Sounds doable. I checked the fluid levels and cleaned off the bottom of the dif just so that I could keep an eye on it until I knew how to fix it. I was surprised to find that the dif was full and now it shows no signs of leaking. Is it possible for the seal to have re-sealed its self? Thanks again. Last edited by MudBoy2; 03-17-2008 at 01:45 PM.

03-17-2008, 03:42 PM	#4 (permalink)
FlyingLow Registered User Join Date: Jul 2007 Location: Van Island BC Posts: 93	Sometimes they leak through the splines and when you remove the d/s from the flange a teaspoon will leak out. This is not really fixed with the seal replacement. It will have to leak a lot to change the oil level significantly. A little oil goes a long way when it comes to making a mess though. Won't hurt to clean it up though and monitor it. __________________ 77 FJ40 36 TSLs, 45 springs in rear, 8274, ARB rear, TBI 2F 97 4 Runner Ltd TLCA# 9203

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