1981 Pickup Rear 4 Link

[TSG]

Recently discovered some frame rot above the drivers side rear spring hanger that has caused some issues with the leaves and has got the whole back end of the truck tweaked a few inches (DS wheel base = 103" and PS wheel base = 107"). I figured it's as good a time as any to just link the rear and cut off the rot as it likely isn't confined to this one spot.

To this extent, I've been doing a bunch of reading (4 link bible, how's my numbers, etc. etc.), but would like some feedback on how best to approach the 4 link. The common theme I've been reading is "don't overthink it", but I am.

A few starter questions:
1. How to start the mock up - full droop, full compression, ride height?
2. Where to set the pinion angle? Point it at the t-case and run a double cardan or single CV drive shaft?
3. Seems like anti-squat is the big factor most folks target first. For a southeast rig (mainly slow speed crawling), is 100% anti-squat a good target? I've read some places that up to 120-130% is good for this type of wheeling.

I'm working through the 4 link calculator and will post some screen shots once I get my initial measurements figured up.

Spec's on the rig:
- Typical Toyota garage build - RUFs, dual cases, stock 22R on propane, 40" trep stickies, full hydro
- This is a southeast wheeling rig, we mainly do slow crawling, but the rain does require some wheel spinning at times.

I ordered up the RuffStuff generic double triangulated 4 link kit and really just need to find some time to start.

I'll continue in a new post with some pics because nobody reads a thread without them.

 

[TSG]

A photo chronology - it all started in 2008 with in a decent condition (although the rust was hiding)

OCD got the best of me and tore it down as a pseudo-restoration project:

Then I met some assholes and started wheeling it:

And how she sits today:

 

[Arickvan]

Recently discovered some frame rot above the drivers side rear spring hanger that has caused some issues with the leaves and has got the whole back end of the truck tweaked a few inches (DS wheel base = 103" and PS wheel base = 107"). I figured it's as good a time as any to just link the rear and cut off the rot as it likely isn't confined to this one spot.

To this extent, I've been doing a bunch of reading (4 link bible, how's my numbers, etc. etc.), but would like some feedback on how best to approach the 4 link. The common theme I've been reading is "don't overthink it", but I am.

A few starter questions:
1. How to start the mock up - full droop, full compression, ride height?
2. Where to set the pinion angle? Point it at the t-case and run a double cardan or single CV drive shaft?
3. Seems like anti-squat is the big factor most folks target first. For a southeast rig (mainly slow speed crawling), is 100% anti-squat a good target? I've read some places that up to 120-130% is good for this type of wheeling.

I'm working through the 4 link calculator and will post some screen shots once I get my initial measurements figured up.

Spec's on the rig:
- Typical Toyota garage build - RUFs, dual cases, stock 22R on propane, 40" trep stickies, full hydro
- This is a southeast wheeling rig, we mainly do slow crawling, but the rain does require some wheel spinning at times.

I ordered up the RuffStuff generic double triangulated 4 link kit and really just need to find some time to start.

I'll continue in a new post with some pics because nobody reads a thread without them.

i dont think ive ever seen these words in one sentence before - "southern low speed crawling"

i think 70% anti squat is a typical trail rig number, but thats up to you and your style of wheeling

the pinion angle is dependent on the 4link geometry

- skip to like 13 mins in and youll get an idea, but read up on the link bible again and then again

 

[TSG]

Awesome. That was a super helpful video. Hopefully can get in the garage this weekend and pull some measurements and get some preliminary calculator outputs worked up.

Unfortunately the ‘slow’ part is the most the clapped out 22R will give

 

[Snowy]

Awesome. That was a super helpful video. Hopefully can get in the garage this weekend and pull some measurements and get some preliminary calculator outputs worked up.

Unfortunately the ‘slow’ part is the most the clapped out 22R will give

I totally get the slow SE wheeling. Contrary to popular belief, there’s a fair amount of wheeling in Harlan, Windrock, etc, that doesn’t require an LS, 42’s and tons to wheel the rock trails and have fun.

 

[chaplinfj60]

as goofy as it sounds pull it in the shop and just cut the back frame off, (not till you have about 90% of the parts, like heims and stuff. then roll axle back once all the excess is out of the way. i struggled getting a clear idea of what i as doing when i had all the excess frame in the way, once i cut it off it just started to come together.

like every said, use link formula and watch a bunch of vids, and then this is where the slippery slope starts, it could be argued that since i am here why not upgrade the rear axle, maybe a fj80 axle, or something. lol

start looking at other rigs too.

 

[TSG]

I think I came to this same conclusion this weekend. Went ahead and started cutting for a flat belly to get my final driveshaft placement worked out. I’ve got all the brackets and heims so I’m about ready to just start cutting and figure it out from there


Been seriously thinking about a different rear axle but it’s not currently in the cards.

 

[Penetrode Offroad]

Nice platform!

 

[chaplinfj60]

ive beat on a IFS rear axle along time and what gave up both times was the ring and pinion. if you can solve that your golden. but i think going links will stop alot of the shock load i was putting on R P because of leafs loading and unloading.

 

[TSG]

ive beat on a IFS rear axle along time and what gave up both times was the ring and pinion. if you can solve that your golden. but i think going links will stop alot of the shock load i was putting on R P because of leafs loading and unloading.

The guys in our group are all running IFS rears (some 4 cyl and others 6 cyl diffs) on 37 - 40" stickies and we haven't had too many broken ring and pinions. The broken ones seem to be more common in the 4.10 ratio and welded. I'm running 4.88 and broke the pin in my lunch box locker the last trip out, but the R&P was fine minus a couple of small chips on the pinion. I'm switching to a full carrier (Grizzly) locker to hopefully help prevent breakage.

 

[Aisin]

A properly set up 3rd member will break shafts before the ring and pinion.

 

[Alex123456]

A properly set up 3rd member will break shafts before the ring and pinion.

This has been my experience also. I've pulled a couple of pairs of rear shafts with twisted splines but never broke a r&p

 

[chaplinfj60]

and mine were both welded 410s

:))

 

[TSG]

Got all the old rear suspension pulled out today and started pulling the tape measure. I posted over in the "hows my numbers" thread previously to get some feedback but didn't want to clutter that one up with a bunch of iterations.

Here is the output based upon how everything seems to layout the easiest. In an ideal world, my lower links would be flatter, but I'm trying to put them in a place where they won't hang up on everything.

I would appreciate some feedback.