3rd member swap advice

[demon322]

it's probably just my paranoia speaking, but the bottom cap bolt in the last pic looks like it's not tightened all the way, because the parting line looks too wide. It could just be an optical illusion, maybe check it with a torque wrench, or check it with some really small feeler gauges.

Ha. Good eye. It definitely isn't loose but I didn't put a torque wrench on it yet until I can confirm the spec. I believe it's 90ft lbs but not positive. Will definetly confirm before the install

 

[demon322]

In all likely hood, the thrust buttons are still in the suregrip. You are lucky and have the clutch type so they can be removed easily. Look through the axle splines where the axles go in and see if the buttons are in there.

If so, they are simply held together with a pin that is flared on the ends. They need to be knocked out.

So I don't need the thrust buttons because my axles have the green bearings installed, correct? I didn't see anything but again am not positive what I'm looking for. Here's pictures of both sides.

 

[demon322]

if the u joints are not the same, the conversion u joint will be fine unless your making some power....just make sure you get the right one for your yoke,
inside clips or outside locating tabs

Thanks. Hopefully I'll get lucky and they will be the same. If not good to know the conversion joint is an option.

 

[demon322]

If you have stock adjustable tapered wheel bearings on your axles you need to have the thrust plug (button) installed in the middle of the diff. If you have aftermarket sealed ball type axle bearings (commonly referred to as green bearings, non adjustable) you do not. There is much debate on whether greens are OK to run on the street. My personal opinion is that factory style tapered rollers are superior. If you have tapered rollers you will need to read up on axle adjustments.

If the u joint is a different size you will need to order a "conversion" joint. They are commonly available. Do not intermix the u joint retaining straps between the small (7260) and large (7290) joints. They appear very similar and can be confused but are dimensionally different.

Checking backlash and pattern can be done now, however if the used gearset has been run for any length of time with a bad pattern and backlash it will be worn and will always be noisy even if you try to correct it. If the backlash is ballpark you should just leave the adjustments alone. Do check that the pinion nut is tight.

This is a prime time to check the sure grip clutches. They could be worn out and it may act as an open differential. They can be replaced. Also prime time to service the rear brakes and axle seals.

Your speedo will read all wrong with the new gears. If it bothers you the drive gear in the transmission will need to be changed.

There is also some debate on if you need to run a gasket between the third member and housing. Again my opinion is that it should be there as it spaces the third member slightly forward for proper axle alignment.

All of the above procedures are in the FSM. Dr. Diff is a good source of parts and info.

Good luck and have fun. The difference with 3:91s will blow your mind.

My new axles had the green bearings already installed, so hopefully they will be ok on the street. Sounds like I just need to make sure the thrust button isn't there.

Not really concerned about the speedo as it has been off since I went to these tires. I checked it with my phone gps and know where safe cruising speed is. I'll be switching to autometer speedo with gps when I get to that part of the build so no worries there.

The other suggestions are very helpful. I just need to get my laptop back from being repaired so I can study my FSM which is on a disc and go over these procedures you mentioned to check backlash and sure grip clutches.

Thanks for the kind words. I can't wait to feel the difference between this open 3:23 set and the new 3:91 sure grip setup. Should be a fun project for sure.

 

[rustycowll69]

So I don't need the thrust buttons because my axles have the green bearings installed, correct? I didn't see anything but again am not positive what I'm looking for. Here's pictures of both sides.

View attachment 1715041281

View attachment 1715041282

yeah. the button is missing. it looks kinda like two metal mushrooms connected by thin metal pin that works like a tiny axle. like what was already said green brgs don't require the buttons

 

[Richard McLaughlin]

I ordered today, a new parts 3.91 sure grip 3rd member from "Webby" who is a well respct member here.
Was $1,250
Looking forward to it!