first time rear end swap

[rich006]

I'm about to do my first rear end swap and I'm looking for general advice about how to do it--what order to do things, how to hold up the new rear during the process, etc etc. I found a really helpful thread here, but I want all the tips I can get. I'll be replacing the leaf springs at the same time. I have access to a military hobby shop with a lift and a pro mechanic on duty, so I'm thinking I'll use that instead of my garage.

More background: In preparation for a front disk swap on my '74 Swinger, I decided to change to LBP, and it seemed the easiest way was to swap in a 8 1/4 rear end (it's a 2.71 sure-grip). I got ambitious and decided to replace the springs too, with 5-leafs from ESPO. Here's what I have:
- the rear end, backing plate to backing plate, cleaned and painted
- shock plates and U-bolts from the donor car, also cleaned and painted
- all new brake parts (except I'm reusing the existing parking brake cables)
- new 5-leaf springs (ESPO) and rear shackle bushings
- the drive shaft from the donor car, which is shorter than my existing one by the same length that the 8 1/4 is longer than the 7 1/4 (donor car was a 74 Valiant 4-door, but I don't know what engine and trans were in it because the front of the car was cut off already)
- new U-joints, already pressed into the driveshaft
- new shocks
- LBP wheels (new tires to be mounted soon) and lug nuts
I think I have all the parts; I just need to get started. Here are some pictures:

some of the "new" wheels (sand blasted and sprayed with Duplicolor silver wheel coating, followed by Duplicolor clear matte):

 

[TrailBeast]

You know, there was a time when a "rear end swap" could be a bad thing.
That's what we used to call it when the rear of the car came around on ya.

Nice rear by the way.

 

[Lecki6]

Well I've yet to do this but will eventually so be sure to keep us updated! One tip I can give yah is I think you are missing a wheel

 

[67Dart273]

The problem with hobby shops is if you get hung up and "need something" then what?

If you have a goodly supply of tools at home, and a decent floor jack, it's not that hard. I'm assuming you are young and in good shape.

Either get a pair of those HF under-tire dollys or make something to roll on. Then all you need to do is jack up the car, unbolt "everything, and let the rear of the springs down on the ground, so the axle is on your dollys.

Pull the front spring eyes out, and snake the springs out of there. Then pull the axle on out

Even I as an old guy, "if I had the time" could do this.

Now I DID use my hoist, but for me, this means if the car had to stay there all night, no biggie. On the hoist, I got the rear shackles "all but ready" to come apart, with the nuts "finger on."

Pulled the U bolts, brake lines, etc (Go to the parts store and get 3/16 inverted flare plugs, and a "union" or two. Now you can plug off the tube on both ends)

Then let the hoist down so either the tires are on the ground, or get the axle on stands, etc

Then just pull the rear shackles. and let the springs down. EASY

 

[Sedanman]

The previous trans was probably a 904. What trans is in your car now? If it's a 904 your good to go. I'd change the rubber line now if I were you. Did you check the bolt size for the front of the spring to see that it takes the same in the front hanger? I would also change the axle end seals before putting it all together. It sounds like your good to go besides those few minor things. Is that the original gear oil in the axle? To swap the disc brakes you will need the prop valve and disc/drum master. I'd stay 1" and under on the master bore.

 

[rich006]

The problem with hobby shops is if you get hung up and "need something" then what?

If you have a goodly supply of tools at home, and a decent floor jack, it's not that hard.

Good food for thought. I'll swing by the hobby shop today and ask what happens if I come up short of a part while my car is on the lift.

Now I DID use my hoist, but for me, this means if the car had to stay there all night, no biggie. On the hoist, I got the rear shackles "all but ready" to come apart, with the nuts "finger on."

Pulled the U bolts, brake lines, etc (Go to the parts store and get 3/16 inverted flare plugs, and a "union" or two. Now you can plug off the tube on both ends)

You mean cap off the lines to keep the fluid from draining out?

Then let the hoist down so either the tires are on the ground, or get the axle on stands, etc

Then just pull the rear shackles. and let the springs down. EASY

I guess maybe I'll think it was easy after I've done it.

The previous trans was probably a 904. What trans is in your car now? If it's a 904 your good to go.

It was and I haven't changed it.

I'd change the rubber line now if I were you.

Did that when I bought the car 18 months ago.

Did you check the bolt size for the front of the spring to see that it takes the same in the front hanger?

Good question. I'm not sure how I'd check that before removing the existing springs though. Does anyone know if they are different between 7 1/4 and 8 1/4?

I would also change the axle end seals before putting it all together. It sounds like your good to go besides those few minor things. Is that the original gear oil in the axle?

I considered changing all the seals, but the axle seals looked good (to my untrained eye). I had to pull the axles to swap backing plates because this rear came with 11" brakes. When I pulled them everything looked clean and the rubber seemed soft. I did replace the pinion seal because I think it was leaking. I think I got the bearing preload reset correctly.

 

[rich006]

Stopped by the hobby shop today to ask what if I get stuck. It's only $4/day on the lift, so even if I leave it there a few days it will still be the least expensive part of the job. I should have some updates tomorrow evening.

 

[diymirage]

it is very doable, it took me a few hours (plus several days to wait on the shop, to have my driveshaft cut and welded)

and I did it on the ground, you should be fine

 

[RedFish]

I roll the complete assembly, springs, tires, everything out and back under again. Bolt front spring eyes, rotate rear spring hangers up into place. reverse of how it was dropped. Thing is, without a lift, some very tall stands placed ahead of the front spring eyes are required.
Some types of lift get in the way of this R&R too. Good luck

 

[dennday67]

When I swapped to super stock springs I had to drill out the front hangers for the bigger bolts for the front eyelets. 5/8" I think. I later swapped to a new front shackle that offered a 1" drop. Easy swap. Unbolt the drive line and try to leave it in the transmission till your ready for the other so you done leak tranny fluid. Unbolt the front and rear hangers and take it out as a unit.

 

[Sedanman]

Just make sure you get it as high as you can go so it will roll into place or leave the wheels off until it's under the car then jack it up and install the wheels and use a jack stand under the one you put a wheel on so you don't throw off the balance and it slides off the jack.

 

[rich006]

Well shoot, I had a long post going about my plan and how it went today, but then I clicked "go advanced" and I lost it. Short version is, my son and I went to the hobby shop and I'm glad we did even though the car is staying there overnight and it's 4$/hour, not $4/day as I thought. For us, it was worth a lot having the mechanic there to help out and all the extra tools I wouldn't have had at home, not to mention the lift. After 7 hours of work we have the front mounting brackets started with the new springs on and the new rear loosely U-bolted to the springs. All that's left is to get the rear shackles mounted, tighten the U-bolts, install the new driveshaft, new shocks and brakes, and take her for a test drive. I'm hoping the install will go quicker than the removal now that we know what's what, but since it's father-son time I don't mind if it takes a while...as long as we eventually get to drive the Dart out of there.

One thing I didn't realize is that the spring mounts and shackles would have to be removed from the car frame. The bolts were installed so that they can't come out unless the whole mount is removed. I assume that's a safety feature, but it made more work than I planned on.

Also, thanks to 67Dart273 for the great tip on plugging the brake lines. Too bad the parts shop only had one inverted flare fitting cap. I plugged the other side with a bolt, but it dripped all day.

And thanks to bcschief who posted the tip to use a box wrench to squeeze the parking brake cable tabs to get the cable out of the backing plate. I think 14mm was the size that worked for me. Easy as pie!

 

[67Dart273]

You mean cap off the lines to keep the fluid from draining out?.

Yes. Where the rear flex hose hooks to the tube should be 3/16 inverted flare. You need a union and a plug for the tube end, and a plug for the rear axle, unless you don't care about fluid

inverted flare union

inverted flare plug

 

[rich006]

You need a union and a plug for the tube end, and a plug for the rear axle

Aha, I guess the union is for the hard lines along the axles? I left those open and didn't have any problems with fluid draining out. But I sure could have used a second plug for the flexible hose.

 

[rich006]

Finished the job today after spending the morning doing Easter stuff. At 5:00 we got kicked out of the shop, but we had done everything by then except bleed the brakes. I drove the car out of the shop using only the parking brake and parked in the boatyard outside. When we went to bleed the brakes we discovered that the left rear spring shackle was inverted so it was pushing the spring up against the trunk pan. Too bad the shop was closed! At that point our only option was to go home (in the other car) and come back with a floor jack. We were able to flip the shackle by jacking up the car by the frame rail, then holding the shackle down with a pry bar while lowering the car. There's only a dime-sized dent in the trunk pan.

We finished bleeding the brakes just as it was getting dark. I think there's still a little air in the system, and I'm pretty sure my inverted flares are all crap (had to tighten the fittings a lot more than I think I should have had to). But I can deal with all that stuff. The big job is done, and the car looks way more bad-*** than it did. I'll get some pix up tomorrow.

On the drive home I noticed a creaking sound coming from the area of the front of the passenger-side spring. I wonder if I need to tighten the bolt on the eye bushing? Or it could have been coming from the shock on that side?

 

[67Dart273]

Great!!

Here's a true story from the old days at NAS Miramar.

The lot of the hobby shop was sloped in places, and the worthless teenager who worked in the tool room was supposed to filter people, IE tuneups or simple jobs could use the sloped stalls. He had given a "hilly" spot to some guys who rebuilt a Ford "Y" block, and............

One day I went out in the lot just in time to see a mess in "happening"

Guys had about a 59/60 Ford pickup were trying to put the engine trans back in. They had an over-extended cherry picker, had lost control, and I guess two of the guys on the back "for ballast" had stepped off.

I got there just in time to see the tail of the transmission stuck right through the windshield........and draining ATF all over the dash.

I was an ETR-2 GCA RADAR tech at Miramar from 70-74. Worked part time at the hobby shop.

 

[rich006]

The rear sits up a lot higher than it did, though I think the rears springs settled a little more on the drive home than they are in the "after" picture. To me it looks much better already but the front probably needs to be raised an inch or so.

before:

after:

 

[66fyssh]

Success!!! And...you had some great bonding time with your son!

Maybe raise the front slightly. Then you'll have to have it aligned.

The rear sits up a lot higher than it did, though I think the rears springs settled a little more on the drive home than they are in the "after" picture. To me it looks much better already but the front probably needs to be raised an inch or so.

before:

after:

 

[66fyssh]

Great story. Sounds like you walked in at the right time. Also sounds like something a bunch of military guys will do. Anything to get the job done, only it didn't quite work out for them that time!

I was active duty Air Force stationed at Little Rock AFB. Not long after I started dating my current wife I bought an 84 Jeep CJ7. I spent a lot of time at the Auto Hobby shop. So one day, I'm at the Auto Hobby Shop working away on my Jeep and the guy working there yells, "Hey Trace, the Colonel is on the phone and wants to talk to you." I was a little freaked out so I ran to the phone and and said, Sergeant Trace. It was my girlfriend...

In the end he was right. I've been married to "the Colonel" for 18 years now!!

Great!!

Here's a true story from the old days at NAS Miramar.

The lot of the hobby shop was sloped in places, and the worthless teenager who worked in the tool room was supposed to filter people, IE tuneups or simple jobs could use the sloped stalls. He had given a "hilly" spot to some guys who rebuilt a Ford "Y" block, and............

One day I went out in the lot just in time to see a mess in "happening"

Guys had about a 59/60 Ford pickup were trying to put the engine trans back in. They had an over-extended cherry picker, had lost control, and I guess two of the guys on the back "for ballast" had stepped off.

I got there just in time to see the tail of the transmission stuck right through the windshield........and draining ATF all over the dash.

I was an ETR-2 GCA RADAR tech at Miramar from 70-74. Worked part time at the hobby shop.

 

[YoungDart75]

My oh my how similar we are. I just picked up a 8 1/4 and will be overhauling it and replacing my 7 1/4 this winter. However I want to replace all the brakes and lines on my 75 Swinger and possibly go with PST's Complete manual disc brake conversion kit. I'm still running the stock 904 right now and stock 75K mile slant 6. Mind if I might ask if your running a slant and 904 trans?

 

[RPMagoo]

-- I'm about to do my first rear end swap and I'm looking for general advice about how to do it--what order to do things, how to hold up the new rear during the process, etc etc. --
-

-- Wheels off - driveshaft out - un-hook the brake line & emergency brake cable - un-bolt U bolts - Place floor jack under the center section of the rear -- swing the rear free of the springs ( OR - drop the springs as per post #8 & 9 )-- pull it out from under the car, while it is balanced on the jack. -- Reverse the order when putting the new one in. -- This assumes that You are working on the floor, with the car supported on jack stands. -- I have done this, several times, while working alone. The rear will balance on the floor jack nicely. --

 

[rich006]

My oh my how similar we are. I just picked up a 8 1/4 and will be overhauling it and replacing my 7 1/4 this winter. However I want to replace all the brakes and lines on my 75 Swinger and possibly go with PST's Complete manual disc brake conversion kit. I'm still running the stock 904 right now and stock 75K mile slant 6. Mind if I might ask if your running a slant and 904 trans?

Yes, I have a slant and 904. The rear end was the first step of a big bolt pattern front disc conversion, which is now complete.

 

[draginmopars]

when I do the swap with out a lift
car on jack stands
I put a pair of tire-less rims on,
floor jack under the rear to take the weight off the springs
remove leaf spring bolts
drop the rear shackles
remove the floor jack
roll the rear out