Rearends
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7T8 Custom
Well-Known Member
Suregrip or one-tire-fire? Gear ratios currently in cases?
Aspen500
Well-Known Member
Better be careful grabbing rear ends. Grab the wrong one and you could be in trouble. Sorry,,,,,,,,I HAD to.
Yes sir. The first one we lifted into the truck, popped my back out. So, there won't be any rear grabbing tonightBetter be careful grabbing rear ends. Grab the wrong one and you could be in trouble. Sorry,,,,,,,,I HAD to.
mike2
Well-Known Member
where about are the rears located ? I may be interested if not too far from north west nj
Great job slant6Billy!
For others to know, the FMJ 8¼” will be a direct bolt in for any FMJ car built between ’76 to ’89 – with exception of propeller shaft length (slightly shorter (1.6”) than 7¼” shafts are).
The dimensions are:
Perch center to perch center is 44.460”
Backing plate to backing plate (measured at axle housing) 54.340”
Drum to drum distance (where wheel bolts to) 58.500”
Axle shaft centerline to rear most U-joint centerline (for propeller shaft length difference) 11.69”
Note: these dimensions are the same with the FMJ 7¼” axle except for above distance is 10.09” – so one will need to shorten the propeller shaft 1.6” if installing an 8¼” in place of a 7¼”.
The ’70 B-body 8¾” assembly dimensions are:
Perch center to perch center is 44.00” (0.23” shorter per side)
Backing plate to backing plate (measured at axle housing) 54.906” (54-29/32”)
Drum to drum distance (where wheel bolts to) 60.13” (about 0.8” wider per side)
Axle shaft centerline to rear most U-joint centerline (for propeller shaft length difference) 12.35”
Other than differential width (0.8” wider per side) and spring perch difference (0.23” narrower per side – which is almost mute) – this is almost a direct bolt in.
The ’73 B-body 8¾” assembly dimensions are:
Perch center to perch center is 47.30” (a lot wider – will need new perches)
Backing plate to backing plate (measured at axle housing) 54.906” (57-47/64”)
Drum to drum distance (where wheel bolts to) 63.00”
Axle shaft centerline to rear most U-joint centerline (for propeller shaft length difference) 12.35”
This differential might need to be cut down to make workable.
Slant6billy – this unit may be worth its weight in gold to someone with a ’71-73 B-body – for this might be one of the hardest of ALL Chrysler differential housings to find. I would highly suggest advertising this on FBBO (and a bit more than $400).
BudW
For others to know, the FMJ 8¼” will be a direct bolt in for any FMJ car built between ’76 to ’89 – with exception of propeller shaft length (slightly shorter (1.6”) than 7¼” shafts are).
The dimensions are:
Perch center to perch center is 44.460”
Backing plate to backing plate (measured at axle housing) 54.340”
Drum to drum distance (where wheel bolts to) 58.500”
Axle shaft centerline to rear most U-joint centerline (for propeller shaft length difference) 11.69”
Note: these dimensions are the same with the FMJ 7¼” axle except for above distance is 10.09” – so one will need to shorten the propeller shaft 1.6” if installing an 8¼” in place of a 7¼”.
The ’70 B-body 8¾” assembly dimensions are:
Perch center to perch center is 44.00” (0.23” shorter per side)
Backing plate to backing plate (measured at axle housing) 54.906” (54-29/32”)
Drum to drum distance (where wheel bolts to) 60.13” (about 0.8” wider per side)
Axle shaft centerline to rear most U-joint centerline (for propeller shaft length difference) 12.35”
Other than differential width (0.8” wider per side) and spring perch difference (0.23” narrower per side – which is almost mute) – this is almost a direct bolt in.
The ’73 B-body 8¾” assembly dimensions are:
Perch center to perch center is 47.30” (a lot wider – will need new perches)
Backing plate to backing plate (measured at axle housing) 54.906” (57-47/64”)
Drum to drum distance (where wheel bolts to) 63.00”
Axle shaft centerline to rear most U-joint centerline (for propeller shaft length difference) 12.35”
This differential might need to be cut down to make workable.
Slant6billy – this unit may be worth its weight in gold to someone with a ’71-73 B-body – for this might be one of the hardest of ALL Chrysler differential housings to find. I would highly suggest advertising this on FBBO (and a bit more than $400).
BudW
And to add an update, Gator pulled the stuck brake drums and (Drum roll Please) the 70 rear is a SURE GRIP 741 with 2.94 gears. Iwant to keep it and go find an F body to stick it in. My logical responsible side says sell it for 600
I'm right over the Commodore Barry Bridge , off Route 322 / Route 45. I think the 70 is staying with me for now, unless I get persuaded. the 73 may be available, we can get a 2nd from the other 73
Kernel Sanders
Well-Known Member
Yes these rears are difficult to find for sure. Canada used the 8.75 in some of the BBodies up to 74. They are perfect for use in 71-79 BBodies. 73 and 74 were set up with the rubber buscut mounting garbage but can easilly be deleted with the earlier spring mounts.
I currently have one for sale but I am in Canada just want to show off this rear as its in amazing shape for a Canadian rust-belt rear lol
It is a 73 8.75 and I've converted it to an ISO delete along with the antiswaybar (I do have a second antisway bar complete for these rears as well. Here are pics of the setup withe extra thick Ubolts.
Almost new brakes and bushings and all new seals and bearings from drDiff.
Looking nice!
Too bad they are not a FMJ bolt in (at least not without mods).
BudW
Too bad they are not a FMJ bolt in (at least not without mods).
BudW
Kernel Sanders
Well-Known Member
Thank you and exactly (re drop-in) and I'm not sure how well width-wise the wide rear will fit on an FM or J car. I know the front track is definately not as wide so the rim back spacing would have to paid attention too
This was going to be used to replace the 8.25 in my 74 Charger but I got an offer on the car I couldn't refuse and the purchaser didn't want to pay the extra for this rear nor the loaded big block ISO delete Kmember with 11.75" brakes with all new bushings and joints and steering components.
Backing plate to backing plate
54.340” vs. 57.734” (about 3.4” wider total / 1.7” wider per side)
Perch center to Perch center
44.46” vs. 47.30”
If a person got some offset wheels for rear (moved center of wheel 1.7” inboard) then differential width wouldn’t be a problem.
One couldn’t rotate tires in that case, though.
The perches can be cut off and re-welded so that wouldn’t be a problem.
Here are a few pictures I swiped from this site (one is mine the others are other members here).
I don’t think you can move the rear wheel outwards 1.7” on any of these cars, without running into quarter panel lip interference (without getting offset wheels, that is).
M-body
F-Body
BudW
kkritsilas
Well-Known Member
You may be able to get wheels with 1.5" greater back spacing and make up most of the difference there. It would probably cost a lot, unless you were willing to run different wheels on the front and on the back; a lot of "front wheel drive" type wheels would proabably fit and work, but you run into the different wheel styles issue. I suppose one way would be to put front drive wheels on all 4 corners, and run 1.5" wheel spacers on the front wheels only.
I am asking this because I don't know: How hard is it to narrow a rear end? I know the housing would need to be cut and re-welded, and shorter axle shafts would be required. What I am aking about is how diffiicult is it to do this at a shop and have everything come out properly aligned? I knkow that some people do this when they narrow rear ends to put really big tires in the rear, usually in conjuction with rear wheel tubs.
I am asking this because I don't know: How hard is it to narrow a rear end? I know the housing would need to be cut and re-welded, and shorter axle shafts would be required. What I am aking about is how diffiicult is it to do this at a shop and have everything come out properly aligned? I knkow that some people do this when they narrow rear ends to put really big tires in the rear, usually in conjuction with rear wheel tubs.
My thinking is custom axle shafts are needed when making extreme power and running fat traction tires. ( I'm really not looking to break anymore axles). 30 years ago (About, anyway), my dad who was a skilled pipe fitter/ steamfitter and most important - welder got sick of my axle breaking nonsense. We went from 7 1/4s to 8 1/4s to a 8 3/4 with a bearing issue. We went and got two Ford 9 inch rears out of a local yard for 50 bucks each. I think they came out of some big car or van, but still 5 by 41/2 bolt pattern. Both were 4:11 ratio and limited slip. These were with an offset center, so one axle was much shorter than the other. My dad removed the longer side shaft and cut the tube down to where the 2nd short shaft would be used. He made a jig to hold the axle housing straight, but it allowed the flange end to slide in towards the center. I don't remember how much he cut down, but he had measurements from the center of the carrier and had some test fits before the welding. Where that rear is today? Who knows?
MoparKidD-4
Well-Known Member
I did some reading up to check the dimensions for swapping a C-body 8 3/4 housing into my cousin's 1971 Satellite/Road Runner project... apparently they are the same, or at least close enough to where we took the 8 3/4 out of his 1972 Dodge Polara and had it rebuilt with 3.55 gears and Sure-Grip. Nice thing about the C-body rears is they almost all had the '489' case.
Actually, all 8¾” after ‘68 (? On year) are 489 cases.
BudW
BudW
