Lost on what to do with rear end - trying to swap

[siggyfreud]

Hey all,

Been doing some searching and reading on swapping rear ends. I'm a bit lost on what I'd need to do, and the parts (trailing arms, perches, etc.)

Currently my 66 GMC has a Dana 60 8-lug rear with leafs. Not sure what it's from. From my reading, swapping it over to a 5-lug disc is more pain than just finding something already 5-lug from a later year.

I understand that the later model (like 72+) rears are wider and will require different back spacing.

Does anyone know if the later model rears with leafs will bolt right into the 66 perches. And what are the trailing arms and how do they mount? My 66 doesn't have anything other than the rear end, leafs, and shackles holding it together.

OR . . . Is this an opportunity to switch over to coil springs, and if so, is there much benefit. I see that CPP offers some coil spring kits and trailing arm kits, and just curious what the process would be to convert and the benefits.

In any case, if anyone has some direction on what rear end I should be sourcing, and the best approach for getting it in, I'd be very thankful. A lot of searches yield 6-lug to 5-lug swaps, or discuss options using the factory 12-bolt.

Thanks all!

[Clyde65]

If your leaf spring, stay leaf IMO.

Are you wanting to go 5 lug for a particular reason?

What is wrong with your D-60?

[siggyfreud]

The front I swapped to for disc brakes is 5-lug. Mainly I like the wheel options available in 5-lug more than eight, and the disc conversions are more readily available. I'd like to have disc in the rear as well, but swapping the D-60 to a 5-lug setup, and then figuring out disc brakes on it seems cost-prohibitive.

[b.sharp]

Newer model leaf spring rear ends have a different mounting pad position. They are parallel with the frame instead of parallel with the trailing arms. Newer trucks do not use trailing arms. That ended in 72. You would have to add the leaf spring brackets or cut and move the spring pads to the factory location on a newer rear end. you could use a standard 1/2 ton truck rear and convert it to 5 lug with new axles and disk brake conversion. Just my .02 worth.

[Old Truck Man]

use the five hole rear from 73 up pickups on leaf spring GMC trucks. You simply weld the spring perches and shock mounts from the 6 hole rear on the newer one. On the newer trucks one shock is forward and one shock rearward. Of course you can have your present axles drilled If you have a 6 lug rear. not a option on the 8 lug rear. But you still have to convert the brakes. The later 73 up rearend gives you a larger range of rear gear ratios and a better choice of rims.

[siggyfreud]

Originally Posted by b.sharp

Newer model leaf spring rear ends have a different mounting pad position. They are parallel with the frame instead of parallel with the trailing arms. Newer trucks do not use trailing arms. That ended in 72. You would have to add the leaf spring brackets or cut and move the spring pads to the factory location on a newer rear end. you could use a standard 1/2 ton truck rear and convert it to 5 lug with new axles and disk brake conversion. Just my .02 worth.

So if I read you right you're saying grab a 1/2 ton rear from a 73+ truck, move the spring pads, and then use a 5-lug/disc brake kit for a 73+ to convert it how I want?

[siggyfreud]

Originally Posted by Old Truck Man

use the five hole rear from 73 up pickups on leaf spring GMC trucks. You simply weld the spring perches and shock mounts from the 6 hole rear on the newer one. On the newer trucks one shock is forward and one shock rearward. Of course you can have your present axles drilled If you have a 6 lug rear. not a option on the 8 lug rear. But you still have to convert the brakes. The later 73 up rearend gives you a larger range of rear gear ratios and a better choice of rims.

Not sure I understand what you're saying. Will I need 2 additional rear ends for this? Saying I should get a 5-lug rear from a 73-up, and then get a 6-lug and take the spring and shock mounts and weld them to the 5-lug?

[chevy_mike]

If you want to keep the same width of the '63-'70 axle housing, you can use any 1/2 ton axle from that era. If you get one that was used of a leaf spring truck, you shouldn't have to mess with any of the mounts (GMC one typically were leaf spring more often). Once you have the axle housing, buy a set of "conversion" axles that will bolt in but have 5 lug pattern OR take the 6 lug axles that would be in this swapped housing and have it plugged and drilled for 5 lug.

If you use a '71 or later housing, it will be wider and push any wheels out further, which could create problems if you are trying to match a deep offset that you might have in the front. If you are buying wheels and don't need the offset to match front to rear, then this might not be any issue to you. If you find a '71 or '72 leaf spring 1/2 ton axle, it should bolt in and already have 5 lug.

As for swapping to trailing arms, I find they ride and handle better then leaf spring setups. That would be your call. If you did swap over, you can find these same years for a trailing arm axle and it would bolt in but there are a number of other things you need outside of the trailing arms and mounts on the crossmember. Shock mounts, panhard bar, spring mounting cups, etc. Might not be worth doing.

[siggyfreud]

Originally Posted by chevy_mike

If you want to keep the same width of the '63-'70 axle housing, you can use any 1/2 ton axle from that era. If you get one that was used of a leaf spring truck, you shouldn't have to mess with any of the mounts (GMC one typically were leaf spring more often). Once you have the axle housing, buy a set of "conversion" axles that will bolt in but have 5 lug pattern OR take the 6 lug axles that would be in this swapped housing and have it plugged and drilled for 5 lug.

If you use a '71 or later housing, it will be wider and push any wheels out further, which could create problems if you are trying to match a deep offset that you might have in the front. If you are buying wheels and don't need the offset to match front to rear, then this might not be any issue to you. If you find a '71 or '72 leaf spring 1/2 ton axle, it should bolt in and already have 5 lug.

As for swapping to trailing arms, I find they ride and handle better then leaf spring setups. That would be your call. If you did swap over, you can find these same years for a trailing arm axle and it would bolt in but there are a number of other things you need outside of the trailing arms and mounts on the crossmember. Shock mounts, panhard bar, spring mounting cups, etc. Might not be worth doing.

Thanks for the info! I haven't bought any wheels yet, and don't plan to until the front and rear are set in place. That will allow me to get what I need. Sounds like finding a 71-71' leaf setup would be the easiest.

[chevy_mike]

Originally Posted by siggyfreud

Thanks for the info! I haven't bought any wheels yet, and don't plan to until the front and rear are set in place. That will allow me to get what I need. Sounds like finding a 71-71' leaf setup would be the easiest.

That would be the easiest but likely the hardest to find. Start by looking in 1/2 GMC trucks, as they are most likely to be leaf). Chevy's had them but they were on option, trailing arms was standard for them.

You're likely going to have better luck finding a '63-'70 rear end (heck I have one spare) and putting in conversion axles. In many ways this is better as the aftermarket axles are stronger and will have no wear on them. The 6 lug backing plates/brakes don't have to be changed, just put '71-'72 drums on with the new axles. Did this on my old '68 years ago (not the one in my signature).

[siggyfreud]

Originally Posted by chevy_mike

That would be the easiest but likely the hardest to find. Start by looking in 1/2 GMC trucks, as they are most likely to be leaf). Chevy's had them but they were on option, trailing arms was standard for them.

You're likely going to have better luck finding a '63-'70 rear end (heck I have one spare) and putting in conversion axles. In many ways this is better as the aftermarket axles are stronger and will have no wear on them. The 6 lug backing plates/brakes don't have to be changed, just put '71-'72 drums on with the new axles. Did this on my old '68 years ago (not the one in my signature).

I assume that along with conversion axles companies sell disc conversions to fit those converted axles? Really aiming for disc all the way around.

[kenny_strong]

Too bad your not closer, I have the rear-end to solve your problems. Never fails. Wrong coast.

[chevy_mike]

Originally Posted by siggyfreud

I assume that along with conversion axles companies sell disc conversions to fit those converted axles? Really aiming for disc all the way around.

Check out my '68 build to see more but here is a link to my rear disc conversion. I got the brackets from a member who was building them. This post has most of the pics showing the conversion, http://67-72chevytrucks.com/vboard/s...1&postcount=39

Most disc conversions that work for a '73-'87 12 bolt truck axle would likely work with the conversion axle setup.

[Softpatch]

Nice truck
.
I used a complete set up from a 72 in my 63 the rear is wider... 1" wider
when i went to aftermarket tires and wheels I was glad for the inch
.
dang I wish were closer
I have a complete 78 P/U 1/2 ton 5lugs
ps,pb tilt 350/350 disc up front with sway bar
i would sell you cheep
but as per forum rules can not tell you how cheep
but you would be suprized
.

[Captainfab]

I agree that if you want a 62" wide rear differential, you will want a '64-'70 12 bolt. I omitted the '63 since they have pressed on backing plates. And then convert to 5 lug. However I have installed a '73+ 12 bolt under a '66 GMC without moving the spring pads. They are off by just a little and there was enough movement in the springs to bolt it up. But the '71+ differentials are 63.5" wide. This may or may not be an issue depending on how wide of tires you plan on running on the rear.

I make 3 different rear disc conversion brackets for the 5 x 5 wheel stud pattern.

The Portland Swap Meet is coming up in a couple weeks (April 4th, 5th and 6th), you could likely find the differential you are needing there.

[BigDan3131]

See this is why when I swap to discs I will be keeping the 8 lugs. I know wheel choices on smaller wheels under 17" are limited but I plan to large by huge. There is a guy who's been trying to sell a set of 22" forever...

Another option is to have the Dana converted from full floater to semi and you can get any axle bolt pattern you want and still keep the strength the Dana offers.