4wd long travel advice

ryan_towry

Member
Posts
17
Reaction
0
so i am trying to build my first go fast offroad build and being me i cant just bolt on a TC kit and want to build it myself, and i am cheap so i am trying to redneck as much as i can from off the shelf (kinda) parts.

so far i have gotten a free stripped 90's toyota to build on (thanks josh), a ford 9" rear out of a 67 f-100 cheap for the rear so now my parts collection goes to the front. i found a 8.8" irs diff from a 04 explorer i think i can get for around 200. after searching i found the drive shaft shop will make stubs for it to mate up a inner 930 and then use the 97-03 ford outer as pointed out by partbarge in the "steering with 934.5" thread with the dodge unit bearing to keep the 5x5.5 bolt pattern already on the 9".

so i got two big questions right now:
1) do you think the 8.8/930 inner/ford outer/dodge unit bearing will hold up to a mild 300-350 HP 327and turbo350 in a 4k pound truck with 37's? how about with 35's? i would hate to design the front around these parts just to find they break all the time and piss me off and have to start over.

2) i have noticed most trucks on here (besides the pro4 trucks) have the a arms set to angle slightly down at ride height giving a roughly 60% up/40% down travel. seeing that in the 4wd design the biglimiter is the CV angle ( i am planning to keep it to about 25-30 on the inner) should i try and adjust this to be more 50/50 for more droop and keep the CG low or is it smarter to have more up than down? i am just trying to use as much of the 25 degree up and down and need to set how much i want up and down to set the diff height based on where that puts the tire in full compression.


sorry if this is basic to you guys but i am still designing and learning and any help is much appreciated. i really just want to learn as much as i can, the challenge of the design is what i love so much.

thanks in advance,

Ryan
 

ryan_towry

Member
Posts
17
Reaction
0
ok so i crunched some rough, rough numbers and if i can get the 8.8 from flange to flange to be roughly 12" and use a 22" a arm and a 3.5" bearing offset and 3" upright offset it, assuming a 60 degree overall travel for 30 each way shows as about 23" of travel (like i said this is really hypothetical)

if i plan for a 10 degree down angle at ride height that leaves me with 40 degrees up and 20 down, meaning that 22" travel turns into 15.33 up and only 7.66 down, this semms a little low on the down travle side right? would it be better to keep it lower and try for a 50/50 distribution? i have only done slow speed design for rock crawlers and wheelers that use more of a 25% up/75% down idea to keep them low but i kow this is a totally dieeerent beast.


has anyone setup a 4wd front that had the aa arms angled down at ride heoght and the drive axle flate to increase the ground clearance without sacraficing the 50/50 distribution and keeping the front axle as close to strait while inder power to make it the strongest? i think you could compensate for the axle plunge with camber adjustment right?
 

scottm

Well-Known Member
Posts
1,864
Reaction
509
That's a lot of questions.. Try searching the shop section with keywords like camber and ride height.
 

ryan_towry

Member
Posts
17
Reaction
0
Yeah I have been searching and reading alot recently, like 4 hours a day for the last week and a half since I have been home alone and have already learned alot and am continuing to learn I just thought I would add some more specific questions and try and gain the knowledge on both routes. I figured as soon as I start dimensioning and designing I could post up in here too cause I think there are a could others pondering similar builds. From what I have seen.

I have read through Mosebuilt's Toyota based buggy thread and looked through the steering with 934.5's thead and the TLT Tacoma and a couple others. Any others that come to mind that I can search for?
 

Ryan B

Well-Known Member
Posts
356
Reaction
9
you could spend years building a front end that will most likely not be strong enough to hold up to offroad abuse, and won't handle 1/2 as good as a chaos setup. 23" of a-arm 4wd travel will require huge $$$ to build, and maintain.

best advise http://chaosfab.com/
 

ryan_towry

Member
Posts
17
Reaction
0
but where is the learning curve there? i have as much fun building it and testing as driving.

i know it will not be cheaper to build or easier, but i really want to design and build it myself even if it takes longer. maybe that is the engineer in me.
 

partybarge_pilot

Well-Known Member
Posts
6,541
Reaction
1,366
As the suspension angle increases the required turning angle decreases.

Here is an Excel file to help you figure out the combined angles that I got from someone (I forget who).......
 

Attachments

partybarge_pilot

Well-Known Member
Posts
6,541
Reaction
1,366
And, 930's should hold up with 35's if your running an open front diff.

The JD fab F150 kits have the option to go to a 934 inner as 37's on a heavy truck tend to blow up 930's. Stick with factory Ford outers, the Empi replacement units have smaller balls and have a much lower torque rating.
 

ryan_towry

Member
Posts
17
Reaction
0
thanks for the info and the spread sheet. i will have to add that into my final design.

it keeps coming up as much as i would love to run 37's, 35's keep sounding better and better.

when you say 930's we are talking stock, raceprepped or with the cromo cages and upgrades?
 

partybarge_pilot

Well-Known Member
Posts
6,541
Reaction
1,366
Race prept wit Chromo cages. Either GKN or Lobro, non of that Chinese crap. Also, the F150 outers have enough angle to them that the inner 930 will be the limitng factor on travel even with steering figured in.
 

ryan_towry

Member
Posts
17
Reaction
0
good to know about which brand is strongest, i had heard some talk about how the german ones were better from my boss who races a 930 in autocross but i did not know which ones those were.

hopefully i can sratch up the coin to get a new PC since my last one took a dump and my wifes mac that i am using now wont run solidworks. once i get that i will try and throw together some dimensions on what i am planning for a visual.

I also think i found a 04 explorer rear diff for 150 i can hopefully pick up monday.
 
Top