Questions on Moving Rear Axle Back for 4r70w

[Ol'Blue]

Im planning my 4r70w install which will be 1.5" longer than my C4/Dana 20 in a cut Bronco. The rear axle is too far forward anyways, so my thought is to install these Duff Axle Alignment plates to move the axle back 1.25" to avoid shortening the driveshaft and getting the wheels closer to center of the well.

https://dufftuff.com/product/lubr-lift-block-axle-alignment-plate/

I have read you can just drill new holes 1" forward in the leaf spring perches but these seem like a stronger alternative. I have WH heavy duty U-bolt and U-bold plates, so I figure I could drill the U-bolt plates to align with the Duff alignment plates and Im good to go? I have checked for axle travel clearance; brake lines have enough slack and shouldn't have any wheel rub.

The alignment plates are 1/2" think and I dont need more lift, so I plan to remove the bottom two WH leafs to make up the difference. Will removing the two bottom leafs change the rid? * The alignment plates ar about the same length at the bottom leaf ~8".

How do we like my plan?

Thanks,

 

[72ford]

Probably not a good idea to remove springs


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[rocknhorse76]

Just drill your perches and plates. It works fine.

 

[Yeller]

I would do it, I have their spring plates, I like them. No issue removing leafs, we do it all the time to tune the ride height. Probably only need to remove 1 of the springs, you’ll loose a little more than the thickness of the leaf.

The issue with just drilling the stock plate is it get short and is more apt to bend. It’s been done with success, I’ve also seen it done in failure.

 

[rocknhorse76]

I would do it, I have their spring plates, I like them. No issue removing leafs, we do it all the time to tune the ride height. Probably only need to remove 1 of the springs, you’ll loose a little more than the thickness of the leaf.

The issue with just drilling the stock plate is it get short and is more apt to bend. It’s been done with success, I’ve also seen it done in failure.

Yeah I always forget how short the stock perches are. I’ve been running aftermarket perches for so long now lol. Those plates are probably a better idea.

 

[Yeller]

Yeah I always forget how short the stock perches are. I’ve been running aftermarket perches for so long now lol. Those plates are probably a better idea.

They are short, it doesn't take much to get the front of the perch to collapse after moving the pin that far forward, which lets the rear axle get loose and then bad things can happen.

 

[Shimmy]

i think your plan works fine. BUT, if you don't need any more lift i'd probably consider redrilli g the perch an inch back vs. the duff plates. IMO, any time you can avoid a lift block of any kind is best

 

[jamesroney]

Im planning my 4r70w install which will be 1.5" longer than my C4/Dana 20 in a cut Bronco. The rear axle is too far forward anyways, so my thought is to install these Duff Axle Alignment plates to move the axle back 1.25" to avoid shortening the driveshaft and getting the wheels closer to center of the well.

https://dufftuff.com/product/lubr-lift-block-axle-alignment-plate/

I have read you can just drill new holes 1" forward in the leaf spring perches but these seem like a stronger alternative. I have WH heavy duty U-bolt and U-bold plates, so I figure I could drill the U-bolt plates to align with the Duff alignment plates and Im good to go? I have checked for axle travel clearance; brake lines have enough slack and shouldn't have any wheel rub.

The alignment plates are 1/2" think and I dont need more lift, so I plan to remove the bottom two WH leafs to make up the difference. Will removing the two bottom leafs change the rid? * The alignment plates ar about the same length at the bottom leaf ~8".

How do we like my plan?

Thanks,

Who is "we?" I'm sure that you will find someone that thinks it's a great idea. But I hate it.

But if you are running the specs in your sig line, then you are currently running Wild Horses 3.5 springs, and you already have the HD u-bolts and plates. But what you might not know is this:
1. Your rear axle with stock perches already has incorrect pinion inclination. Installing a longer transmission will make it more incorrect.
2. Your rear axle stock perches are too short. Adding hardware to the spring will not make them longer.
3. Wild Horses sells Heavy Duty springs, and heavy duty hardware, which INCLUDES heavy duty spring center bolts with oversized heads. You will have to make sure everything fits. Certain vendors with low cost leaf springs made in India have 10mm center bolts. Wild H uses full 7/16.

Do yourself a favor. Remove any existing shims and factory perches. Buy these, and clock your rear axle correctly. (pinion down 1.5 degrees at ride height,) Don't go back more than 1 inch or so, or else your rear axle will get into your fuel tank. (if you don't have a 23 gallon tank already, then you should...)

https://dufftuff.com/product/weld-on-leaf-spring-perch-66-77-bronco-bronco-2/

If you know how to drill a hole, you can buy these and save some money.

https://www.wildhorses4x4.com/early-bronco-anti-wrap-leaf-spring-perches

That's what I would do. And yes, I usually delete the very bottom spring in the leaf pack, because the long perches are a little taller.

 

[Shimmy]

Who is "we?" I'm sure that you will find someone that thinks it's a great idea. But I hate it.

But if you are running the specs in your sig line, then you are currently running Wild Horses 3.5 springs, and you already have the HD u-bolts and plates. But what you might not know is this:
1. Your rear axle with stock perches already has incorrect pinion inclination. Installing a longer transmission will make it more incorrect.
2. Your rear axle stock perches are too short. Adding hardware to the spring will not make them longer.
3. Wild Horses sells Heavy Duty springs, and heavy duty hardware, which INCLUDES heavy duty spring center bolts with oversized heads. You will have to make sure everything fits. Certain vendors with low cost leaf springs made in India have 10mm center bolts. Wild H uses full 7/16.

Do yourself a favor. Remove any existing shims and factory perches. Buy these, and clock your rear axle correctly. (pinion down 1.5 degrees at ride height,) Don't go back more than 1 inch or so, or else your rear axle will get into your fuel tank. (if you don't have a 23 gallon tank already, then you should...)

https://dufftuff.com/product/weld-on-leaf-spring-perch-66-77-bronco-bronco-2/

If you know how to drill a hole, you can buy these and save some money.

https://www.wildhorses4x4.com/early-bronco-anti-wrap-leaf-spring-perches

That's what I would do. And yes, I usually delete the very bottom spring in the leaf pack, because the long perches are a little taller.

i like this the best but that assumes OP can weld or has access to a shop to do this.

 

[Ol'Blue]

Who is "we?" I'm sure that you will find someone that thinks it's a great idea. But I hate it.

But if you are running the specs in your sig line, then you are currently running Wild Horses 3.5 springs, and you already have the HD u-bolts and plates. But what you might not know is this:
1. Your rear axle with stock perches already has incorrect pinion inclination. Installing a longer transmission will make it more incorrect.
2. Your rear axle stock perches are too short. Adding hardware to the spring will not make them longer.
3. Wild Horses sells Heavy Duty springs, and heavy duty hardware, which INCLUDES heavy duty spring center bolts with oversized heads. You will have to make sure everything fits. Certain vendors with low cost leaf springs made in India have 10mm center bolts. Wild H uses full 7/16.

Do yourself a favor. Remove any existing shims and factory perches. Buy these, and clock your rear axle correctly. (pinion down 1.5 degrees at ride height,) Don't go back more than 1 inch or so, or else your rear axle will get into your fuel tank. (if you don't have a 23 gallon tank already, then you should...)

https://dufftuff.com/product/weld-on-leaf-spring-perch-66-77-bronco-bronco-2/

If you know how to drill a hole, you can buy these and save some money.

https://www.wildhorses4x4.com/early-bronco-anti-wrap-leaf-spring-perches

That's what I would do. And yes, I usually delete the very bottom spring in the leaf pack, because the long perches are a little taller.

Thanks for the input everyone,

@jamesroney

1. yup, new trans is 1.5" longer and why I'm shooting for moving axle back 1.25"-1.5" to help alleviate increase in incline. I have a 23 gallon tank and have to room to move back ~2".
2. got it
3. I have the WH heavy duty springs

I dont weld but I have considered replacing the spring perches and agree its the best option. I suppose I could remove the existing purchase, mock everything up, set the pinion angle and clamp it all down and tow it to my welder OR mock it all up, pull the axle and have it welded.

The WH perches are advertised as "anti-wrap" and is something else I need, but was looking at this version

https://www.wildhorses4x4.com/early-bronco-wrap-trap-axle-anti-wrap

Do you think the perches will be enough to reduce anti-wrap or should go for mor? Running a mild 351w.

Thanks,

 

[Shimmy]

Thanks for the input everyone,

@jamesroney

1. yup, new trans is 1.5" longer and why I'm shooting for moving axle back 1.25"-1.5" to help alleviate increase in incline. I have a 23 gallon tank and have to room to move back ~2".
2. got it
3. I have the WH heavy duty springs

I dont weld but I have considered replacing the spring perches and agree its the best option. I suppose I could remove the existing purchase, mock everything up, set the pinion angle and clamp it all down and tow it to my welder OR mock it all up, pull the axle and have it welded.

The WH perches are advertised as "anti-wrap" and is something else I need, but was looking at this version

https://www.wildhorses4x4.com/early-bronco-wrap-trap-axle-anti-wrap

Do you think the perches will be enough to reduce anti-wrap or should go for mor? Running a mild 351w.

Thanks,

another option is to see if there's a local mobile welder. i don't know how to weld so i've mocked things up and had a mobile welder come by to finish the job.

 

[Ether]

Replace the perches and move axle back 1", looks so much better, perfect pinion angle, and keeps tire away from the fender better.

 

[jamesroney]

Thanks for the input everyone,

@jamesroney

1. yup, new trans is 1.5" longer and why I'm shooting for moving axle back 1.25"-1.5" to help alleviate increase in incline. I have a 23 gallon tank and have to room to move back ~2".
2. got it
3. I have the WH heavy duty springs

I dont weld but I have considered replacing the spring perches and agree its the best option. I suppose I could remove the existing purchase, mock everything up, set the pinion angle and clamp it all down and tow it to my welder OR mock it all up, pull the axle and have it welded.

The WH perches are advertised as "anti-wrap" and is something else I need, but was looking at this version

https://www.wildhorses4x4.com/early-bronco-wrap-trap-axle-anti-wrap

Do you think the perches will be enough to reduce anti-wrap or should go for mor? Running a mild 351w.

Thanks,

If you are anywhere near Fremont, CA 94536, just bring it by and I'll weld it for you for free.

I'll bet there's no shortage of Bronco welders somewhere near you. Post your location in your profile and someone might be willing to help out.

I recommend that you do this: "I suppose I could remove the existing purchase, mock everything up, set the pinion angle and clamp it all down and DRIVE IT GENTLY TO MY WELDER."

Or tack them in place with a stick welder so they don't move until you can final weld them. There's plenty of room to lay a nice bead on the perches while it is in the Bronco.

I run the Wild H anti-wrap perches, but the one's from Duff are very similar. The longer perches are helpful, but not sufficient, to control wrap. The Wrap Trap has proven itself "pretty good" at preventing the wringing off of the driveshaft, and the associated destruction of the Dana 20 output shaft. So the answer is:
"I needed more." and I'm running 35's with an anemic 302. But I drive harder than some.

 

[Ol'Blue]

Really appreciate the offer James, but Im in Socal and my welder is only about 2 miles away, so when Im ready I'll gently drive or trailer it there.

At some point I also planned the extreme duty TC output system which will extend things even more 3/4"-1.3" so I think I'll hold off on the transmission swap until Im ready to do everything at one and get it dialed in once and for all.

Hopefully between the HD perches, wrap trap and HD output system I will be able prevent another driveshaft annihilation.

 

[Tricky Dick]

I'll gently drive or trailer it there.

Trailering sounds the win to me. I wouldn't trust them to stay put even with gentle driving. Either way, I'd be double checking the position before the final burn in. Make some marks with a sharpie after you get them set for a quick visual check.

 

[DirtDonk]

In a pinch, you could drive it in front wheel drive. But then you’d have to remove the driveshaft and then put it back in for final mock up.

 

[Tricky Dick]

In a pinch, you could drive it in front wheel drive. But then you’d have to remove the driveshaft and then put it back in for final mock up.

And don't brake.

 

[Ol'Blue]

And don't brake.

Yes, exactly!

 

[Ol'Blue]

Thanks for all the help gents. I think I have my plan figured out although you might see more questions here when I actually get going on it in a couple of months.

Parts list just got longer.........

Im taking the trans to California Performance Transmission tomorrow to be Dyno tested. I hope its turns out okay, I rebuilt it myself.

 

[rocknhorse76]

Thanks for all the help gents. I think I have my plan figured out although you might see more questions here when I actually get going on it in a couple of months.

Parts list just got longer.........

Im taking the trans to California Performance Transmission tomorrow to be Dyno tested. I hope its turns out okay, I rebuilt it myself.

I rebuilt my 4R70W myself a few months ago, and it works great! My dyno test simply involved driving the h@ll out of it behind my 408W though As long as you followed all of the instructions, air checked the pistons, and your clutch pack clearances checked out, you should be good to go.