Pre 70 rear ends vrs 70 and newer

[abadsvt]

Does anyone know the measurments between the different rear ends? I know the pre 70 is shorter than the 70 and newer but by how much? Is there an easy way to tell what year I have or is it just measuring from axle flang to axle flang? My rear wheels are too wide by 1/2" or so per side. Any measurments would be VERY much appreciated. Thanks alot

Josh

[Longhorn Man]

70 was when they chainged, some of the early ones were narrower than the later ones... the majorityu of 70 rear ends tend to be the wide ones.
I can't find my book with the measurements... i know it is a 3/8 inch per side increase in late 70 verses early 70.

[abadsvt]

Originally Posted by Longhorn Man

70 was when they chainged, some of the early ones were narrower than the later ones... the majorityu of 70 rear ends tend to be the wide ones.
I can't find my book with the measurements... i know it is a 3/8 inch per side increase in late 70 verses early 70.

So there is only 3/8 per side for a total of 3/4" difference between the different years. Is that the same for the pre 70 rear ends? I am hoping the pre 70 are around 1- 1 1/2" narrower. That way i don't have to narrow my rear end. Thanks

Josh

[raggedjim]

I thought it was 1.5" difference (.75 each side) I'll see if I can find out...

Rg

[Longhorn Man]

jim... you might be right. I can't remember now.
SOMEONE has the measurements.
You triied a search? It's been covered a dozen times this year alone.

[raggedjim]

I've found a couple of threads that say it's 1.5" but it's basically relying on the guys post (don't we always do that?) Here's one, there are others out there as well...

Rg

http://67-72chevytrucks.com/vboard/s...d.php?t=180781

[uncle]

It's 3/4" per side.

[abadsvt]

Originally Posted by Longhorn Man

jim... you might be right. I can't remember now.
SOMEONE has the measurements.
You triied a search? It's been covered a dozen times this year alone.

I did try a search but didn't find anything. What did you guys type in for the search to find that thread?

If it is 1 1/2" that would be perfect. Do you guys know what a 67 rear end width is and what a 70 rear end width is? Before i buy a 67 rear end i want to make sure i don't have the a 67 rear end. Thanks alot for you guys help! I really appreciate it.

Josh

[lolife99]

abadsvt,... I just measured my extra '69 rearend. If you put a tape BETWEEN the outermost edge of the backing plates,... it measures 55.25". The late '70 and '71-'72 rearends should be approximately 1.5" wider.

[raggedjim]

Josh, you will have to measure your rear end. The 70 could have either the short (around 55") or the long (around 57.5") There's really no way to tell until you measure it... Chevy changed it sometime in the year. I have heard someone say that MOST of the 70's are long, but both the 70's I have had were the short ones so I can't say for sure.

Good luck, Rg

[abadsvt]

Okay so i just went out and measured my rear end. I took my measurement from the out most flange on the rear end. The flange with the 4 holes in it on each side. I got 58.75" + or - . Am i missing something or is my rear end not from out trucks? The axles were 5x5 bolt pattern. I am going to double check my measurement here shortly.

Josh

[raggedjim]

Try measuring between the backing plates (back of one to back of the other). That's what the 57.5" distance was. I know the brake backing plates have an indent where the mounting holes are, I suspect you have the long rear end, which would be good if you plan on getting the short one.

I can double check mine tonight if you need me to. I have 5 rearends in my shed I can check.

Rg

[abadsvt]

Originally Posted by raggedjim

Try measuring between the backing plates (back of one to back of the other). That's what the 57.5" distance was. I know the brake backing plates have an indent where the mounting holes are, I suspect you have the long rear end, which would be good if you plan on getting the short one.

I can double check mine tonight if you need me to. I have 5 rearends in my shed I can check.

Rg

Thanks for helping me out!!!!

I just went down and double checked my measurments. From between the backing plates i got 58". My father said that this is the original rear end but i don't see how that could be because i thought the 70's were only 56.5" and the pre 70's were 55". If that is the case then a 70' rear would work. Here is a quick drawing i did just to make sure we are on the same page. Thanks alot

[raggedjim]

Well, I'll check the ones I have when I get home today.

Hopefully we'll get this figured out!

Rg

[raggedjim]

Ok, I checked ALL of mine (2 - 70's and 3 - 71/72's) and they all measure 58" to the inside of the mounting flanges (just like your pic) I don't have access to a 67-69 but they are shorter (they would probably measure 56.5" in the same area...) I think the differences in the dimensions come in because of the different areas used to start and end (inside mounting flange verses inside outer edge of the brake backing plate, if I used that I got 57" Don't let that confuse you, we have an apples to apples at 58")

You have the longer one.

Good luck, Rg

[Boog]

Originally Posted by abadsvt

Okay so i just went out and measured my rear end. I took my measurement from the out most flange on the rear end. The flange with the 4 holes in it on each side. I got 58.75" + or - . Am i missing something or is my rear end not from out trucks? The axles were 5x5 bolt pattern. I am going to double check my measurement here shortly.

Josh

Josh if your truck is a 70 something has been changed as 70's were still 6 lugs. The 5 on 5 lugs didn't start until 71. Anyway it looks like the narrower rearend would solve your clearance issue by a hair.

[raggedjim]

Boog, you just hit the nail on the head, I completely ignored the 5 lug comment and assumed he was running 6-lug.

Josh, if you go to the narrow rearend you will have to either buy new axles for it or have a machine shop redrill the shorter axles for a 5 lug pattern. They will also have to turn down the center protrusion the drum fits over. I did this once, it's not too tough.

I think I have a drawing of the lug layout I used somewhere... if I find it I'll post it.

Rg

[abadsvt]

The truck was a 5 lug from the day i got it. Now that doesn't mean it was originally a 5 lug because the grandfather restored the truck a long time ago. I know he converted to disc brakes in the front so he might have swapped the axles. I don't mind buying new axles or having them redrilled to fit my wheels. That would be a cheap way to fix my problem. Thank you guys for helping me out. I really appreciate it alot!!

Is there anyone with a pre 70 rear end laying around that could take that measurement to confirm these #'s before i buy a different 12 bolt? Thanks

Josh

[abadsvt]

Originally Posted by Boog

Josh if your truck is a 70 something has been changed as 70's were still 6 lugs. The 5 on 5 lugs didn't start until 71. Anyway it looks like the narrower rearend would solve your clearance issue by a hair.

Yeah if the pre 70 12 bolts would would work it would save me alot of money and not have to buy new wheels. I would be stoked!!!