SOA rear driveshaft setup

[White Stripe]

I did a soa on my fj40. I have a fj80 rear axle with a orion tcase. The fj80 axle doesn't quite line up with the tcase output. The pinion is probably about 3 or 4 inches to the side of the tcase output. I used a toyota pickup rear driveshaft that is shortened because the u joints have a lot more flex in them than the fj40 ones. I do not have a double cardan joint. The drive shaft has a compressed length of 19" from flange to flange, at ride height it is probably about 22" long or so. The operating angle of the shaft is 22 degrees at ride height. I get a fairly bad vibration during the transition of going from acceleration to deceleration/engine braking at around 50 or 60mph. Im fairly certain its coming from the driveshaft. If did it b4 the orion was installed, the sm465 is freshly rebuilt. If I change to stock shackles it will lower the truck about 3/4 of an inch and give me probably a degree less operating angle-not much. I have heard of driveshaft harmonic balancers or insulators on shafts. I have seen lots of insulators on cv axles. I could put a dc joint on but I have heard thats not a good idea with a offset differential. Would appreciate any input.

 

[Chris Wilcox]

The way I understand to do it and how I did mine is you point the pinion up at the transfer case. Use a double cardan mini truck or some fj60 had them i think driveshaft at the TC and run the single u-joint at the axle with a minimal angle. Just enough for it to have some movement. Since you have side offset you'd have the angle regardless. On typical driveshafts U-Joints need to be installed in pairs and there are rules for the angles into and out of the drive shaft. Google that and compare to your setup. One other thing, the u-joints have to be phased correctly. Maybe this is stuff you already know, if so hopefully someone else will have better info.

 

[pandathrust]

If your rear pinion is pointed straight at the output from the transfercase like shown in the attached picture, then use a double cardan as this is the correct geometry for a double cardan drive shaft. Also, given that the pinion isn't exactly inline with the TC output the double cardan should help too. My brother's SOA'd fj62 has a 80 series FF in the rear and has the same issue as you're explaining with the TC output and rear pinion flange not perfectly lined up. We set his up with double cardans on both front and rear drive shafts and he has no vibrations at all. here's a link to his the SOA part of his thread, he probably has info or pics in there that might be worth looking at if your interested My first Toyota.

 

[White Stripe]

How long is your brothers drive shaft? Mine is only about 20 inches long, so if his driveshaft is much longer than their could be a fair difference between my setup and his.

If your rear pinion is pointed straight at the output from the transfercase like shown in the attached picture, then use a double cardan as this is the correct geometry for a double cardan drive shaft. Also, given that the pinion isn't exactly inline with the TC output the double cardan should help too. My brother's SOA'd fj62 has a 80 series FF in the rear and has the same issue as you're explaining with the TC output and rear pinion flange not perfectly lined up. We set his up with double cardans on both front and rear drive shafts and he has no vibrations at all. here's a link to his the SOA part of his thread, he probably has info or pics in there that might be worth looking at if your interested My first Toyota.

 

[pandathrust]

How long is your brothers drive shaft? Mine is only about 20 inches long, so if his driveshaft is much longer than their could be a fair difference between my setup and his.

thats very true. If i remember correctly his was somewhere around 30" so the setup for the DS will probably be different as well. You might want to contact tom wood's driveshafts or some place similar to see what they would recommend you to do given the situation.

 

[White Stripe]

thats very true. If i remember correctly his was somewhere around 30" so the setup for the DS will probably be different as well. You might want to contact tom wood's driveshafts or some place similar to see what they would recommend you to do given the situation.

Good idea, I will make a call and see what they say.

 

[Stumpalama]

If it were me, I would bite the bullet now and tear it down and reset the spring perches to line up correctly with the t-case, point the pinion up and get a dc shaft.
I think you will be ahead in the long run and much happier, rather than chasing your tail for a long time and eventually coming back to just going back to square one anyway.
I'm no expert, but I'm pretty sure that using a non dc shaft with a short wheelbase SOA will cause ds binding and broken ujoints/flanges.

 

[rusty_tlc]

Stupid question, maybe, but did you check to make sure the phasing is correct between the u-joints?

 

[cruisedeisel]

Just line the grease nipples up on each u-joint. The ears will line up.

 

[White Stripe]

Stupid question, maybe, but did you check to make sure the phasing is correct between the u-joints?

Haha well it turns out the drive shaft was one tooth off out of phase. Shaft is back in, it still vibrates during that decel transition, but much less. It's barely discernable now.

 

[rusty_tlc]

Even a blind dog finds a bone once in a while.