SOA supension problem. Front shaft keeps pulling out. (1 Viewer)

[HAMBURGLAR11]

I have an 78 fj40 soa front and rear. I used old man emu springs flipped with a couple of leaves pulled to keep em flat and keep me low. I do have a shackle reversal on the front. i am running 40 inch tires . I have been running this setup for 10 years. Without issue.
Recently the front shaft has been pulling out of its splines on up hill vertical ledges . Even ordered a Tom woods driveshaft with 6” of splines. Witnesses state that the pinion is dropping when I hit the skinny pedal to climb up .

any thoughts? Should I put another spring in? Remove the shakle reversal? Any ideas would be great. Thanks in advance

 

[BMValentine]

Sounds like your springs are wearing out and causing some axle wrap. you could add an anti-wrap traction bar.

 

[too tall]

You could add a suck down point and use your front winch to keep the front diff from pulling away from the truck. You'd maybe be surprised at how much it will help you climb obstacles better. I do have a very long travel front shaft though. 6" isn't very long IMHO.

 

[GLTHFJ60]

Long slip front driveshaft. Need one with a shackle reversal.

 

[cruisermatt]

Sounds like you need to measure for your driveshaft length more correctly. I have a 8” shackle with a shackle reversal and 60 springs, a lot of travel with a stock Toyota slip yoke and have not had a issue, and I wheel more frequently then most. Probably almost 50 full days of wheeling on my current setup over three years.

have you actually fully maxed out your suspension each direction and measured the compressed and extended lengths that the DS needs to be?

 

[HAMBURGLAR11]

On level ground there is only an inch of splines allowing for up travel. On the shaft

 

[HAMBURGLAR11]

You could add a suck down point and use your front winch to keep the front diff from pulling away from the truck. You'd maybe be surprised at how much it will help you climb obstacles better. I do have a very long travel front shaft though. 6" isn't very long IMHO.

I think 6” is plenty

 

[gnob]

Your DL obviously begs to differ.....

I think 6” is plenty

 

[cruisermatt]

What are the distances between the pinion and t-cases flanges with suspension fully extended and compressed? I seriously doubt there’s more then a 6” change with your setup.

 

[peesalot]

My 40 is SOA, shackle reversed, 20 year old Alcans, no leafs removed, front shaft shows 1.75 inch used during uptravel, it has 4.25 inches of uptravel, has never pulled the splines on the shaft and when climbing it will show maybe 3" if passenger front is fully dropped out, like carry the tire , I agree that your springs may be clapped out allowing more droop and allowing the diff to roll a bit, if the bushings are gone and shackles are loose then I could see your problem occuring, check bushings, check for cracked leafs, jack the driver side until front end is air born and see how close the slines are to separating. If the pinion is rotating I would check the u bolts as well, you may have a broken center pin too.

 

[B y r o n]

Have you bothered to measure for drive shaft length at full suspension extension? Sounds like the drive shaft itself is to short.

 

[HAMBURGLAR11]

My driveshaft length on level ground is 28.75 . I will flex it on and see what it does at full droop. I also doubt it will be more than 6 inches. I will Check all mentioned components and report back.

 

[too tall]

What tends to happen with that setup is when you are on a steep climb or "catwalk"while on the obstacle with your tires still spinning, when your tires get close to the ground they will drive the axle away from the chassis. What you might think is full drop can be exaggerated by this situation. With a shackle reversal the front driveshaft will extend further than it would the other way as the hinge point is at the front. As I said above, the best way to control this is to use your winch or rig up some limit straps of some sort.

 

[HAMBURGLAR11]

Checked the bushings they’re fine. i pulled the shaft and am goin to add 1.5 inches to it. as it is an inch shorter than the old one. What do yall think about putting 6* shims in? To help with the axle wrap.

 

[DangerNoodle]

Shims won't help with axle wrap. You really need an anti-wrap bar.

 

[HAMBURGLAR11]

Will do. thanks for the advice