i'm going to make this a basic list that will cover chevy and ford mid and fullsize. anything chevy specific will be denoted by C and ford will be denoted by F. all the ford specs are for I-beam IFS front ends only.
- Straight axle -
- (C fullsize - mostly leaf sprung.. can use dodge front axles as well) (C midsize - leaf sprung jeep front axle or 66-77 bronco coil sprung front axle)
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- (F - F150/Bronco/ranger are coil sprung with radius arms, F250 and larger are leaf sprung)
- C mid and fullsize & F f250 and up - (leaf sprung axle) leaf springs, shackles and frame mounting brackets
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- C midsize and F f150/bronco/ranger - (coil sprung axle) coil spring frame buckets, shock towers, and radius arm brackets
- C&F all - (only a recomendation) most guys who run bigger than 38's recommend running a crossover steering setup. the stock steering setup tends to jerk the steering wheel back and forth. i would recommend this as well. my F150 with the 39.5's shook the wheel with a dual steering stabilizer. when building your own crossover steering for a fullsize chevy, you must use a tie rod end from a 92-94 Jeep Grand Cherokee. a CJ7 arm MAY work as well.
- C all - Transfer case with fixed yoke and matching driveshafts. the IFS tranfer cases have a yoke that locks in with a snap ring and the driveshaft doesn't have a very long split yoke on the shaft itself (front). the rear shafts are slip yoke as well, so it either needs to be cut and made to work with your application (roughly $100) or pick up a shaft from the same body type truck (4x4 version) whether you have std cab/shortbed, std cab long bed, ext cad/shortbed, etc etc. 2wd trucks will need a new transmission (4x4) or run a divorced transfercase which is more complicated.
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- F fullsize - with fords I-beam IFS, you may use your stock transfer case and driveshafts. i recommend upgrading any slip yoke cases to fixed yoke (NP205, 208, 1356). if you have a slip yoke case, you will need to updrade your driveshafts as well, from a truck with a fixed yoke case from the same body type truck as yours (bronco and all F150 front shafts are the same length and are interchangeable).
now.. on 2wd fullside and all midsize chevys, the rear axle is over the leaf spring, instead of under like the 4wd fullsize trucks. you can either do an axle flip by welding spring plates on the top of the axle tube or swap it out and replace it with a 4wd rear(midsize requires an axle flip if using the stock rear). when doing an axle flip, you must make sure you get your pinion angle correct, or else you may damage universal joints and eventually the pinion bearing or pinion yoke.
for the midsize chevys, it's recommended that you pick up a matching rear axle to the axle of choice for the front.
1 other important factor, you MUST ensure you have matching pairs of ring and pinions front and back. if they are of a different gear ratio, you risk breaking something in the driveline. the best way to ensure you have a matching set of axles is to get the front and rear axles out of the same truck. another way you can do so, is by reading the tag which is usually bolted to the rear by 1 of the differential cover bolts. there are other ways of checking the gearing, but they require a little more work. you can get a close estimate by turning 1 axle(while the other is held in place, unless the axle has a locker or working posi) 1 full, 360 degree rotation and counting how many times the pinion yoke turns. for example, a 3.73 ring and pinion set will rotate roughly 3 and 3/4 turns to 1 full rotation of the axle. a 4.10/4.11 will rotate just a little over 4 rotations to 1 rotation of the axle. there is also a formula(which i don't have) that you can use by counting the number of teeth on the ring and pinion(of course, don't add the 2 numbers together).
if doing a SAS in a GM midsize, you will also need to swap your steering box with an astro van box that puts the pitman arm forward(180 degrees off from the stock S10/15 box). you will also need a jeep pitman arm from a CJ7 (i believe, i will check into it to verify that). the stock GM pitman arm has the joint in the arm, whereas any straight axle steering linkage you will be using will have the joint in the steering link.
i hope this helps anyone who is looking into a straight axle swap. if i've left anything out, please inform me and i will revise the post.
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