Thread: drive shaft pinion angle

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I am gonna get a 4 link kit and use my 9" ford rear axle. The kit uses some brackets that weld onto the bottom of the axle to connect the links to. The yoke angle of the rear will be dependant on where radially the brackets are welded on.
I do not have a transmission yet so I don't know how the trans output will be angled.
Is this something I need to wait to do until I have the trans in place, or should I set it up so that the rear yoke points perfectly staight forward and then just place the trans. as close to that line as possible?
Also, when the rear suspension travels, will the axle actually rotate, or does a 4 link keep the axle in the same position throughout the travel?
I don't really know where the rear susp. will settle down to once everything is done. Right now it's just a cab on a bare frame.

well the 4 link on my jeep kept the axle from rotating ..it stayed pointing the same general direction ...i wouldnt think that the pinion angle would be to crutial as long as its as close as possibe to where u think it sahould be ...however if you know the tranny you want you could get the dimentions of it and cut up a cardboard cutout of it ..then use that as yoru referance...also ..isnt the 4 link adjustable? well im just rambling some ideas from what i might do ..but there are lots of smarter pl on this site that can point you in a better direction im sure ..good luck

Read this for a start;

http://www.streetrodderweb.com/tech/0203sr_driving/

and this;

http://www.iedls.com/ptsetup.html

And yes, pinion angle is critical!

To add to Bob's reply:

A four link maintains a constant pinion angle. The axle will not rotate. You really need to have the engine and transmission mounted in the car before setting up the four-link, and the car needs to be sitting like it will ride when finished. There is some adjustment, but you need to get it very close to start with. If you try to mount the rear axle by using some shortcut, you take the chance of having to do it over again.

The kit I'm considering is actually a 4 bar, so it doesn't have adjustable links. Is a 4 link much better for street use?
The most difficult thing I think I'll have with the procedure I just read about will be leveling the car to begin with. My garage has a pretty significant slope to it. I would bet the front of the car is a good 6 inches down from the rear because of the slope, and I already have my jackstands all the way up. I'll practically have to sit the rear frame rails on the ground to get the thing level.
(that is an exageration, but I will have to drop them much too far to install a rear axle) I suppose I could get some major blocks to put the front jackstands on to get the front up.

Any decent 4-bar will have some adjustment. See the attached photo from TCI.

A four link is a racing setup, and is much more complicated than a 4-bar for the street. It's overkill, takes up a lot of room, and is difficult to set up.

Oh.......let's throw some more fuel on the fire!!

You haven't told us how you plan to use the truck. With any of the four bar setups you're looking at coilovers (or bags) for suspension. If you're never, ever, ever going to use your truck to haul anything heavier than a six pack that might work okay.

Warning, some of this is personal preference, justified where necessary!

In my experience the rear four bar arrangements where all four bars are parallel to the frame rails, and are typically mounted as outboard as the axle and frame allow, give the least compliant ride. Great for straight ahead, less friendly on turns and twisties. They leave plenty of room for exhaust routing and are easier to setup. Try to visiualize one end of the axle going over a hump, or the truck leaning in a turn, and imagine how trying to twist those two parallel bars in different arcs can cause some bind.

A more "useful" arrangement is a triangulated four bar. The lower links are similarly placed as the parallel four bars, but the uppers point in toward the center of the vehicle. Because of the different polar moments of the bars, (do the same visualization as above) the upper bar isn't fighting the lower bar. You end up with a better ride, and still have good control. This is essentially the same design the OEM auto guys came up with years ago. They have talented engineers who know about these things. Exhaust routing can sometimes be a challenge, but not insurmountable. Works with bags too.

One other setup that utilizes rear coil springs (or bags again) is a trailing arm type. Look under GM pickups, NASCAR cars, and hot rods with a Pete & Jakes/SoCal arrangement. These use two long bars (P&J calls them a ladder bar) angling toward the center as they go forward, and then some sort of upper locator bar.

All of the coil setups, except the triangulated 4 bar, need a panhard bar or watts link to control lateral movement. Yet
another item to interfere with exhaust.

If you plan to still have some truck function then don't dismiss leaf springs. For all around utility, ride, and reliability they're tough to beat. Not the best ride and handling, but has pluses in the load carrying department.

Just depends on what you want and how you're going to use it.

well, I'm not gonna be hauling anything in the bed or towing anything, or doing any type of racing. . . ever. I'm building this purely for a fun driver. I put a IFS in the front with 2" drop spindles. I want it to sit a little lower than stock and handle descently too, so I want something in the back that will provide a good combination with the IFS. I figured some type of 4 bar or 4 link would be the best way to go.
If leafs would work ok with the IFS considering my goals for this car then I'd like to take that route because of the cost benefits and ease of installation.

Here's one of the P&J trailing link setups Bob mentioned. The front attachments at the frame are urethane bushings. The attachments on the axle brackets are clevises. This type of rear suspension works really well.

I saw the art morrison tri 4 bar set up, there is no price listed though. TCI offers a normal 4 bar with everything you need for $800. Are tri 4 bars about the same, I'd like to stay under that amount.
Is "P & J" a supplier also, I'm not getting much on a search.

P&J is Pete and Jakes at www.peteandjakes.com. However, if you do a complete 4-bar with coil-overs, mounts, etc., it won't be cheap. Triangulated 4-bars may a bit cheaper since you don't need a panhard bar or watts link.

I don't think Jerry does 50's Chevy pickups, though.

You might want to take a hard look at re-working your leaf spring setup. With the right parts, you can get them as low as necessary, they ride fine and they hook up.

The 4 link from TCI comes with coil overs and mounting cross member along with all the brackets and mounting hardware for the entire thing. It's a pretty good deal for 800 big ones.

Originally posted by tcodi
I saw the art morrison tri 4 bar set up, there is no price listed though. TCI offers a normal 4 bar with everything you need for $800. Are tri 4 bars about the same, I'd like to stay under that amount.
Is "P & J" a supplier also, I'm not getting much on a search.

My Art Morrison Catalog lists the 4 bar @ $885.

yeah, I don't actually have the catalog, I'm looking online. The price for the tri 4 isn't listed online. But $885 doesn't sound bad if you get coil overs and all that.

One more thing to include in your planning/cost est (always happens!!), if you do the triangulated 4 bar, if you can't weld well the setup and welding costs are not a small item, and then you'll need to have the axle housing straightened as they will warp from the bracket welding unless it's done in a jig. With the leaf springs you may find a bolt in housing, if you work at it a bit, that won't require that extra step.