[bigunde]

Can anyone tell me what a good replacement rear end would be for a 78 lemans?????????Thanks

[bigunde]

Can anyone tell me what a good replacement rear end would be for a 78 lemans?????????Thanks

[Tom]

You can upgrade from the weak factory 7.5 rear to a much stronger 8.5 rear that was used in the mid 80's Buick Grand Nationals and T-Types.Should be a simple bolt in swap.

Tom

[mike nixon]

you'll want to get an 84-up rear from the g-body. that was the first year the 81/2 was offered. the previous years were 71/2. monte ss used 3:73 ratio ,grand national used a 3:42 ratio, g/p 2+2 had 3:73 also. the lowest factory gear offered wtih the 71/2 was a 3:23. the 81/2 units are a good diff.

watch out for the backing plate being wallowed out from the wheel cyls rotating on the units that didn't have bolt in cyls. mike

[Rick Lightfoot]

Originally posted by mike nixon:
you'll want to get an 84-up rear from the g-body. that was the first year the 81/2 was offered. the previous years were 71/2. monte ss used 3:73 ratio ,grand national used a 3:42 ratio, g/p 2+2 had 3:73 also. the lowest factory gear offered wtih the 71/2 was a 3:23. the 81/2 units are a good diff.

watch out for the backing plate being wallowed out from the wheel cyls rotating on the units that didn't have bolt in cyls. mike

<font size="2" face="Verdana, Helvetica, sans-serif">Mike, all of the Monte SS rears I have seen have been the 7.5" rears. Was the 8.5" available in the SS? I know that the Turblow Buicks and some select 307 HO Hurst Olds had the 8.5"..

['ol Pinion head]

The rear wheelhouses in the '78-87 G series are quite large compared to '64-67 A-body rear wheel houses. A '68-72 A-body rearend will bolt right in a 78-87 A-G series after relocating coil spring perches to the top of housing (same spot as original junky 7.5). We do this all the time. By using the earlier rearend, one also gains inner tire clearance, as the shock mounts go straight back vs angled outwards towards the tires. To do so, one will have to run 68-72 A-body upper arms or adjustable uppers (BMR or Hotchkiss). Retaining stock '78-87 uppers will make pinion point up slightly. Also care needs to taken in choosing rear wheels, as 68-72 R/E is aprox 1 1/8" wider on each side, but usually this is no prob. A narrower '65-67 12 bolt Chevelle R/E can also be used, but nice orig housings for these are really getting expensive....just more $$$ to build. BTW, 8.5 posi GN rearends are not cheap & are very tough to find.

[ June 20, 2002, 07:44 PM: Message edited by: ol' Pinion head ]

[mike nixon]

rick, when i built the diff for my 81 g/p i researched the parts books at the dealer i worked at. according to them the ss used the 8.5 diff in the 86 - up models. it may have been a hd suspension option. i got lucky and found a 3:42 unit from a gn with bent tubes and had moser eng repair the housing. they now build a 9" and a 12 bolt housing for the 78-87 g body.

i've also seen the 8.5 units in diesel equipped a/ g bodies but they always had 2:56 or 2:73 ratios in them so be sure to check the ratio before buying one. mike

['ol Pinion head]

Hmmmm...diesel G-bodys with 8.5's...Oh yeah, OH YEAH

-------------------------------------------------------------------Gone to pull housings & axles...

[ June 22, 2002, 08:35 AM: Message edited by: ol' Pinion head ]