Sheared Differential Input Shaft?

[Toxarch]

Disclaimer: I'm not a gear head, but will wrench on almost anything at least once.

So there is an '77 FJ40 for sale for a good price. The owner said, "This unit is ready for any trail except it needs a new rear end. Current rear axle has a locker but input shaft has been sheared. Will probably require new rear axle." The rear is a full time locker.

Is it better to just replaced the damaged parts? Or would it be better to buy the whole differential and replace the whole thing? What kind of ballpark cost would I be looking at?

 

[amaurer]

Differential input shaft = pinion?

If yes, I'd just get a new third member, setting up the new gears seems like a PITA to me.

 

[inkpot]

Howdy! If it is that great of a rig, and that easy to fix, he would fix it himself and sell it for a whole lot more. Probably a busted pinion, which means a new ring and pinion, plus bearings and setup labor. Or swap in a new third member with the right gear ratio. You can't evaluate the damage without opening it up. There could be more damage. How/why did it break? Too much power, cheesy suspension, lousy driver, etc??? John

 

[craptabulous]

Differential input shaft = pinion?

If yes, I'd just get a new third member, setting up the new gears seems like a PITA to me.

a removable 3rd is probably the easiest differential to set up , try that dana crap .

if you can just find a new third its probably the best choice , i'm guessing he snapped the pinion due to axle wrap .

 

[Toxarch]

Might have been too much power. It's got a 350 in it and it's used as a trail truck.

The '77 had a 4.11 rear end, right? Shouldn't be too hard to find. Would you recommend going to a 3.73 front and rear for better highway speed or is there no need with a 350 engine?

 

[inkpot]

Howdy! Is this rig a SOA setup? Easy to snap the pinion without an anti-wrap bar. BTDT. What size tires does it have, and what transmission? Those all make a difference on gearing applications. Also, are you going to drive it like the seller? John

 

[Toxarch]

Newb here so I don't know what BTDT stands for. It does not have a SOA. It has Rancho RS5000 shocks, 2" body lift, and BFG MT 33x12.5x15 tires. He says the transmission and the transfer case are original.

I plan to make it an occasional driver when I don't need my truck and for hunting in the winter. It won't see a lot of trail riding unless I start heading out with some of the guys on the forum or with a couple of friends with Heeps, but they don't do anything serious. Some of the trails when hunting can get pretty steep and very rocky. But that's only for 4 months out of the year.

 

[rusty_tlc]

Newb here so I don't know what BTDT stands for. It does not have a SOA. It has Rancho RS5000 shocks, 2" body lift, and BFG MT 33x12.5x15 tires. He says the transmission and the transfer case are original.

I plan to make it an occasional driver when I don't need my truck and for hunting in the winter. It won't see a lot of trail riding unless I start heading out with some of the guys on the forum or with a couple of friends with Heeps, but they don't do anything serious. Some of the trails when hunting can get pretty steep and very rocky. But that's only for 4 months out of the year.

If the price is right find a used third and swap it in then wheel the h-e-double hockey sticks out of it. Just make sure you match the gear ratios to the front diff. when you buy your third.

BTW BTDT stands for "Been there done that"

Oh yeah BTW stands for "By the way"


And I'm sure the guys here will be happy to help you find other ways to throw money at it. We're good at that.

 

[inkpot]

Howdy! Been There, Done That. When mine snapped, it trashed my driveshaft by throwing over a cliff, and the pinion gear wedged between the ring gear and the third member housing, effectively putting it in PARK! You might wan to stay with the 4.11's which is better for the trial, unless it will see a lot of highway time. Cost half as much to do, also. Maybe the seller just forgot that even with a 350 in it, it is still a farm tractor, not a Camero. John

 

[Toxarch]

This one still drives so maybe it's not that bad. Most everywhere I go is some highway since I am out of the city. But in an FJ, I wouldn't be in too much hurry to get anywhere.

 

[amaurer]

This one still drives so maybe it's not that bad. Most everywhere I go is some highway since I am out of the city. But in an FJ, I wouldn't be in too much hurry to get anywhere.

How can it drive with a sheared anything-shaft? Its hard to imagine a sheared shaft that is honestly "not that bad" - you can limp it any number of ways, but replacement needs to be done, and always means the same thing.

 

[inkpot]

How can it drive with a sheared anything-shaft? Its hard to imagine a sheared shaft that is honestly "not that bad" - you can limp it any number of ways, but replacement needs to be done, and always means the same thing.

Yea, that is a bit curious. I wonder if it is still in front wheel drive. Maybe the pinoin flange is getting pretty loose, and he thinks it is busted. Just lost it's load. Does it just need a rebuild/reset? John

 

[65swb45]

Yea, that is a bit curious. I wonder if it is still in front wheel drive. Maybe the pinoin flange is getting pretty loose, and he thinks it is busted. Just lost it's load. Does it just need a rebuild/reset? John

Or, it's got a Lockright in it that's banging so hard it sounds like a busted pinion!

 

[Toxarch]

The rear end is NOT locked. It has a locker whick turns the rear axle into positraction, the vehicle is being driven by the fron axel.

Never heard of a positrac locker before. And that answers how it's still driven.

 

[cmiller114]

Buy it, bring it home (on a trailer), break out the wrenches and camera and join the rest of us who are trying to figure out WTF the previous owner/s did!