SAS driveshafts? New driveshafts?

[Littlebeefy]

I'm working on my SAS right now. Using the Duff Monster Swap kit. So far, I'm really impressed by the quality.

I pulled out both driveshafts to clean and put in new Ujoints, but as I was getting ready to pull them apart I had pause: What if they are too short? Shouldn't I make sure they are long enough after the new suspension is in before I go through the trouble?

So, I'll wait and measure, but my question for you is, are there any longer stock driveshafts that I can pull from a salvage that are slightly longer and will work without modification? For example, it seems like the rear driveshaft of a 1980 Bronco is about half an inch longer, but that seems like an irrelevant difference (trigonometry is hard, so I'm speculating). The standard front is one piece and the rear is two piece with the Cardan joint.

To add complexity to this problem, I'm in the process of prepping parts to swap out essentially the entire powertrain. I'm putting in a 460, a ZF5 and an NP205 later this year. At that point I will invest in custom long travel drive shafts, so I just need a stop gap to get me on the road after the SAS until I start the drivetrain swap. My current drivetrain is a 351W with a T170 and NP208 and my rear driveshaft is 4602-GC.

One possible cheap solution for the front is to shorten a driveshaft from an 89 with the M5OD (which I happen to have lying around). That's cheaper than lengthening a rear driveshaft, which is the bigger problem (if necessary).

Also, any suggestions for a source on long travel driveshafts when I do head down that route?

Thanks!

 

[ArdWrknTrk]

You need a collapsible front driveshaft with a double cardan joint at the TC in front, to clear the steering and 460 exhaust.

By putting the shackles in the rear the front axle is going to move into the transfer case.

It will blow the case in half or break it free from the gearbox.

Gary has pictures in his RSK thread.

 

[Littlebeefy]

You need a collapsible front driveshaft with a double cardan joint at the TC in front, to clear the steering and 460 exhaust.

By putting the shackles in the rear the front axle is going to move into the transfer case.

It will blow the case in half or break it free from the gearbox.

Gary has pictures in his RSK thread.

Jim,

I'm not sure I fully understand you. Can you point me to the post; I can't find what you're referencing.

Is this only an issue after the powertrain swap or even just with the SAS?

[ArdWrknTrk]

Jim,

I'm not sure I fully understand you. Can you point me to the post; I can't find what you're referencing.

Is this only an issue after the powertrain swap or even just with the SAS?

Chad,

Think about what's happening when you fix the front of a leaf spring to the frame horn and put the shackle in the back.

You hit a bump, and when the spring arch flattens the axle moves back.

This is what makes the ride better than having the shackle in front.

But the TC is rigidly attached to the gearbox, and the gearbox is attached to the engine.

What is going to give in this situation?

Let me tell you it is not the U-joints, or the motor mounts.

I will have to look back at Gary's posts (or perhaps he will pop in here?)

But the double cardan helps the front shaft 'reach over' obstructions in the range of motion of the axle.

Gary had Big Blue at full droop on the lift and under as much load as he could muster. (I told him to drop it off the lift)

But with all the crap he's packing under the hood and the winch bumper who knows how low it could go in a dynamic situation?

[Gary Lewis]

Chad,

Think about what's happening when you fix the front of a leaf spring to the frame horn and put the shackle in the back.

You hit a bump, and when the spring arch flattens the axle moves back.

This is what makes the ride better than having the shackle in front.

But the TC is rigidly attached to the gearbox, and the gearbox is attached to the engine.

What is going to give in this situation?

Let me tell you it is not the U-joints, or the motor mounts.

I will have to look back at Gary's posts (or perhaps he will pop in here?)

But the double cardan helps the front shaft 'reach over' obstructions in the range of motion of the axle.

Gary had Big Blue at full droop on the lift and under as much load as he could muster. (I told him to drop it off the lift)

But with all the crap he's packing under the hood and the winch bumper who knows how low it could go in a dynamic situation?

This post on Big Blue's Transformation thread is probably the place to start reading. I'll read more of this thread and see what else I can contribute.

[Gary Lewis]

This post on Big Blue's Transformation thread is probably the place to start reading. I'll read more of this thread and see what else I can contribute.

Ok, I've read more. I'm running the double-cardan front driveshaft from a 90's F350. It is just barely long enough, and if it was any shorter I fear it might come out. But being on the verge of coming out means it has the most travel before bottoming out. And that is critical.

What other questions do you have, Chad? Jim?

[Littlebeefy]

Chad,

Think about what's happening when you fix the front of a leaf spring to the frame horn and put the shackle in the back.

You hit a bump, and when the spring arch flattens the axle moves back.

This is what makes the ride better than having the shackle in front.

But the TC is rigidly attached to the gearbox, and the gearbox is attached to the engine.

What is going to give in this situation?

Let me tell you it is not the U-joints, or the motor mounts.

I will have to look back at Gary's posts (or perhaps he will pop in here?)

But the double cardan helps the front shaft 'reach over' obstructions in the range of motion of the axle.

Gary had Big Blue at full droop on the lift and under as much load as he could muster. (I told him to drop it off the lift)

But with all the crap he's packing under the hood and the winch bumper who knows how low it could go in a dynamic situation?

Jim,

I’m not putting leaf springs up front. I’m staying with coils so there is no “arc” except for the radius arm (which is actually getting longer in the swap and therefore wider diameter arc if you count that). Would I need to be concerned about this?

The cardan in the front still makes sense with the longer transmission and the ride height causing crossmember clearance issues in the front shaft, but isn’t long travel sufficient?

[ArdWrknTrk]

Jim,

I’m not putting leaf springs up front. I’m staying with coils so there is no “arc” except for the radius arm (which is actually getting longer in the swap and therefore wider diameter arc if you count that). Would I need to be concerned about this?

The cardan in the front still makes sense with the longer transmission and the ride height causing crossmember clearance issues in the front shaft, but isn’t long travel sufficient?

Sorry, I was under the impression you were doing a SAS/RSK.

I'll have to look into the kit you're installing.

[Littlebeefy]

Ok, I've read more. I'm running the double-cardan front driveshaft from a 90's F350. It is just barely long enough, and if it was any shorter I fear it might come out. But being on the verge of coming out means it has the most travel before bottoming out. And that is critical.

What other questions do you have, Chad? Jim?

So I guess I’m back to the original question. If I’m worried about my driveshafts being too short for the lift from the SAS, is there an option for a slightly longer driveshafts that will get me by until I swap the powertrain? If not, is there another way other than paying to lengthen existing ones? Shortening is definitely cheaper than lengthening, and I have a long one piece for the front that I could shorten. What about the back?

[Gary Lewis]

So I guess I’m back to the original question. If I’m worried about my driveshafts being too short for the lift from the SAS, is there an option for a slightly longer driveshafts that will get me by until I swap the powertrain? If not, is there another way other than paying to lengthen existing ones? Shortening is definitely cheaper than lengthening, and I have a long one piece for the front that I could shorten. What about the back?

Chad - Go to Documentation/Driveline/Driveshafts. Then click on the Application Chart tab and scroll waaaaay down to F-Series 4wd. See the note at the top of the page that says "NOTE 1 - transfer case to front axle NOTE 2 - transfer case to rear axle". There you can see all of the driveshaft lengths and what they were used in.