Should the third member be dropped to replace the pinion seal on an 8.4” rear diff? (1 Viewer)

[SaturnAscends]

This might not qualify as “hardcore,” but the Tacoma section didn’t seem to be very active.

I was at a local off road fab shop the other day, and the guy commented on how much gear oil was getting slung around by the pinion seal on my rear diff. He said this would actually be a major undertaking to the tune of $1400 or so since the supposedly "right" way of doing it involves dropping the third member, installing new bearings, setting pre-load, etc., so the crush washer doesn't mess it up when retorquing the pinion nut. At this point, you might as well install an Eaton e-locker, so that price doubles.

However, the FSM says to check and adjust pre-load with the 3rd still in the vehicle. What gives?

 

[bigredmachine]

you can do it either way. you can replace the seal with the third in the axle but you have to be careful with making sure that you dont over torque the pinion nut causing excessive preload on the pinion. if there are other issues with the third i would pull it and take care of whatever issues there may be

 

[WildernessRimFab]

However, the FSM says to check and adjust pre-load with the 3rd still in the vehicle. What gives

Ive replaced a pinion seal with the 3rd attached. I think the issue with leaving the 3rd installed is that your preload may get messed up from turning the axle shafts incl wheel bearings and rubbing the races on wheel bearing seals. Any minor brake drag would also affect your preload.

If the 3rd seems ok, you can replace the seal on the truck and save your pennies for a full rebuild and locker at a later date. If you are slightly off with your preload when replacing the seal you wont grenade anything that wouldnt be replaced when you rebuild.

You'll also want to get a new pinion locknut.

 

[gnob]

most times you have a leaky pinion seal is because you have bearing issues anyway.

the shop is right, that is the "correct" way to deal with the problem.

 

[WildernessRimFab]

I agree with @gnob on the "correct" way
However...I am guilty of installing a new pinion seal just to limp along for a couple months (years?) until I eventually did a full diff rebuild.
You dont need any special tools outside of a torque wrench and some flat steel bar with a holes drilled in it to hold the pinion flange.

My homebrew tool is below, its nothing special. Holes need to be appropriately sized and located and you'll need to clearance a bit to allow room for the pinion nut socket.

Side note, expect this thread to get booted or shamed out of the hardcore section very soon.