71FJ40 Chevota

[71FJnick]

@Jdc1 yea this weekend his her birthday, so no cruiser work

@SuperBuickGuy thanks for the info, I suspected the front driveshaft wasn't as critical, knowing that it's common to use a standard shaft makes me feel better. I may have some space issues with the sm420 vs TC output flange with a dc shaft anyway.

Thanks!

 

[71FJnick]

Match drilled the pinion flange for the rear today.
I'm using 10mm bolts, grade 10.9 metric or 8 sae.
I think a flanged bolt will fit and have clearance for the u joints.
I used a 25/64 drill bit (9.9mm) and it seemed to work well.
I'll try to drill the parking brake hub tomorrow.

For anyone wondering, here's a shot of the 85 mini truck, stock, and IFS driveshafts at full bend.
Angles from horizontal are roughly:
Mini truck 32
Stock 27
Ifs 16
Pretty incredible, this basically makes my decision for me.
The minitruck will go in the rear (DC)
The stock in the front and I'll probably sell the ifs

 

[handcannon]

For anyone wondering, here's a shot of the 85 mini truck, stock, and IFS driveshafts at full bend.
Angles from horizontal are roughly:
Mini truck 32
Stock 27
Ifs 16
Pretty incredible, this basically makes my decision for me.
The minitruck will go in the rear (DC)
The stock in the front and I'll probably sell the ifs
View attachment 1070925

Excellent pic showing the maximum angles. Very good info.

Don

 

[71FJnick]

Tore into the front axle today.
The goal, install a pinion flange on the front diff so I can have real 4x4.

The good news is that all the seals look fresh and I found no major damage, in fact the axle looks freshly rebuilt.

The bad, my "71 fj40" is now confirmed by the frame ID and front axle to be a 67. To my surprise, I found what I assume to be ball and claw axles.

New plan is to finish assembling this axle and run it until it either breaks or I can afford to swap out to a newer axle with disk brakes and fine splines.

 

[71FJnick]

The diff was in pretty good shape so I replaced the pinion seal, installed the companion flange and torqued the bolt.
Since this has a solid sleeve for the pinion, torque is 150 ft lbs.
Painted the gears and checked the pattern, looked pretty good. And the bearing preload was good, the PO must have set it up before the flange was removed.
I reinstalled the diff and torqued it down (35 ft lbs for the diff to axle studs).

Started putting the pass side back together and broke a bolt
The bolts that hold the spindle to the knuckle seem to need LOW torque.
All refs seem to say 34ftlbs, but this bolt snapped at 20.
I pulled it all apart and will order another bolt and some safety wire.
I'll need to do more research on the torque value.

 

[71FJnick]

Did some searching and found an answer.
For ball and claw axle, spindle to knuckle bolts are 11-16 ft lbs, with safety wire, guess that answers that.
Will order parts and re-assemble next weekend.

 

[SuperBuickGuy]

oops. Just recently I learned something new (to me) about torquing - it stands to reason, but I'd never thought of it - the torque on a bolt is directly tied to its size. A friend was setting up the front differential for my H3, and started to torque the caps (he owns his own mechanic shop) and started doing what Yukon gear said was the proper spec. He stopped and said it didn't "feel" right, so then he did some more searching, got ambiguous answers, and eventually looked up what torque for a bolt size. That measurement agreed with one of the three different values (the Yukon value was 2x what it was supposed to be)... point isn't Yukon is bad, but mistakes can easily happen - even to the guys whose job it is to be right.

 

[71FJnick]

Armed with the right torque specs, blue loctite, and new bolts I went about finishing the front axle assembly today.
Started by cleaning out the knuckle and specifically the bolt threads so loctite would seal.

Packed with moly grease and re assembled the ball and claw axle.

Torqued to 13 ft lbs
Next up is to measure the driveshafts and get them to a shop.

I need to layout options for the axles and suspension if this one breaks or I want to upgrade to disks, whichever is first.
I've considered going back sua with 4" lift springs and 35s, or keep it soa with newer axles. Hopefully I can drive it a bit and see how I like the soa before I need to make a decision.
We'll see how the brakes work

 

[SuperBuickGuy]

yikes, I started out "just replace the front differential" and now have 3 link/4 link and one tons....

 

[71FJnick]

Yea I'm scared of the depths of this addiction... the old I can fix that or make that better.... Just crazy... And a little fun.

 

[SuperBuickGuy]

that said, if you need stock parts, I still have quite a pile of them

 

[71FJnick]

Thanks @SBG PM inbound
<edit> looks like you block PMs, which I understand. Anyway, if you're looking to part with the stock axles from your '71, PM me, I may be interested.

I've read and seen a lot of SOA vs SUA on here
Both seem to function pretty well and deliver results.

Right now I have:
S/R with SOA axles
no drive shafts (measuring this week)
my springs need bushings (I think)
I may need to re-position the hangers for shackle angle
I want to re-weld my front spring hangers as they were "clearanced" for the siganaw box

My End Goal is:
35"+ tires with "mild" offroading
I'm a novice wheeler so I don't know how far I will take the hobby
I like the go anywhere-do anything functioning of these trucks, but really think 4" SUA on 35s or SOA on 35s or 37s will be plenty for what I'm doing.

Editorial comment: 37s SOA look awesome! But looks doesn't mean it's durable or capable.

My concerns are these:
4" SUA
Need front and rear axles and driveshafts
Do i need to do a C&T - I've heard NO but I suppose the C&T depends on shackle length a little
Probably don't need an anti - wrap bar
Rough ride and poor flex - concern but may not matter for my use
Pro- Bolt n go suspension lifts with mostly stock components, or at least components I can purchase

SOA -
Need front axle (maybe rear?) C&T and perches welded
Still need driveshafts (but those are ready to measure today)
Need bushings in the springs
SOA is a bit tall and tippy, I may want to "lower" it
Anti wrap bar needed in rear, maybe in front
Pro- Lots of work has been done, though quality is questionable

So my basic question is this: Should i
a) Continue to repair/fix the POs SOA to make this truck reliable or
b) Convert to SUA, then buy a lift (future), then continue to repair or
c) Get this running and driving SOA, then sell it and buy a different '40 (hate giving up on a project )

 

[SuperBuickGuy]

box is checked, PMs should be good to go...

 

[handcannon]

My opinion--- Get it running safely and drive it. By driving it you will soon know if the current configuration is what you really want. Then you can make decisions based on reality. And, in the meantime you will be enjoying your 40.

Don

 

[71FJnick]

Don- thanks, that's pretty much what I've decided, I'm pretty close (I think) to having something I can drive around the block so that should help with determining what I do or don't like about the set up

@SBG I still can't start a conversation with you... Don't know if the issue is on my end or not, but will keep checking

 

[SuperBuickGuy]

interesting, it worked from my end.

 

[71FJnick]

Man I am on the struggle bus with this PM thing.
Got yours, then clicked "leave conversation" instead of back and lost your email

 

[SuperBuickGuy]

I'll resend

 

[71FJnick]

Killed some time today waiting for the Vet to call.

Mocked up the drive shafts.
'85 minitruck in the rear
I pulled the parking brake drum, knocked out the old studs, rotated the DS by 45deg and drilled for M10x 1.50 studs from Summit
Dorman # 610-308 from Summit Racing
Drilled with 25/64 bit to create .004"-.008" interference with the knurl, they seemed to seat nicely in the drum
I'll need to lengthen the DS as I'm almost a full extension installed. Length looks like 27"

Stock DS up front - no drilling needed
Again I'm at full extension so I need to lengthen to 29"
One problem is that I'm also at full flex on the U joint that attaches to the Transfer Case

I'll do some more investigating, but I may just have to go Double cardan up front as well. This will require some more grinding on the fin of the SM420 transmission, but that shouldn't be too bad.

 

[71FJnick]

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