8.5" Rear modifications

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8.5" Rear modifications

Postby 80 MONZTA » Thu Nov 05, 2009 12:59 am

I picked up a 2 wd Blazer 8.5" rear, going to figure out how to mount a torque arm to it.
I was hoping that it would have 3.73 gears in it, but no luck, it has 3.42 with an open diff. I would almost like to run it as-is just to see how the ratio will work out for me, but then I will need to remove it to install a possi unit. So I am not sure what to do. I plan on using a 26.1" tall tire, using 6th gear with the 3.42's will be iffy under 75 mph, Iowa interstate speed limit is 70. I have been trying numbers at http://www.ringpinion.com/Calc_RPM.aspx and it actually looks like 4.11 gears may be the way to go.
Anyway, I need to get rid of that huge ring around the yoke.
8.5 Rearend B.jpg
8.5 Rearend B.jpg (91.6 KiB) Viewed 2888 times
8.5 Rearend C.jpg
8.5 Rearend C.jpg (79.34 KiB) Viewed 2888 times
The lower web is large enough for an attachment point of the torque arm, and that horizontal hole may be usefull too, the upper web is a bit on the small side but may be able to get some use out of it. I am using this post http://www.forums.h-body.org/viewtopic.php?f=10&t=25789 as a guide for attaching the torque arm.
8.5 Rearend E.jpg
8.5 Rearend E.jpg (71.97 KiB) Viewed 2887 times
How does one actually go about removing the H-body brackets without cutting to much from them? Only way I can think of is to use a thin parting disc and carefully cut at the weld. May be tricky on the round tube. I can see that the Blazer brackets are welded better to the axle tube then the H-body ones are, glad I don't have to save those!
LeRoy
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Re: 8.5" Rear modifications

Postby 72 SS PNL » Thu Nov 05, 2009 2:50 am

my 06 gto cruises at 80mph @ 2000rpm , with the t56 the gto's used the Z06 gearing

for a tq arm i think you need to do something like the GNX used that bolted up as part of the diff cover
first and best car owned 72 GT(changed to SS) panel wagon

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Re: 8.5" Rear modifications

Postby NixVegaGT » Thu Nov 05, 2009 12:17 pm

72 SS PNL wrote:…like the GNX used that bolted up as part of the diff cover


I've always been a fan of that solution. It may work fine to use the webs but It would suck to crack the case. Those 8.5" S10 rears are pretty scarce. Thanks for journaling this. I'm looking forward to seeing how it turns out.
- Nic '73 Vega GT "DogBoxx" Batwing LS1
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Re: 8.5" Rear modifications

Postby 80 MONZTA » Thu Nov 05, 2009 2:38 pm

Dang, now you got me worried that I may crack the case. :(
Do the GNX rears have larger diameter bolts holding the cover on? The bolts seem kinda on the small side to hold a torque arm on, of course there are 10 of them, so maybe it would hold fine?
I was planning on using a cover like this pic (prob not that brand, but one simmilar), maybe I could have some aluminum welded to it?
Or go with a sandwich of steel between the diff and cover, but how thick would that have to be? And then it spaces the cover out, how will that affect oiling of the gears? It would add more oil, so that part would be good.
diff cover.jpg
diff cover.jpg (11.52 KiB) Viewed 2831 times
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Re: 8.5" Rear modifications

Postby 72 SS PNL » Thu Nov 05, 2009 3:35 pm

i believe the bracket was sandwiched between the cover and the diff it self
first and best car owned 72 GT(changed to SS) panel wagon

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Re: 8.5" Rear modifications

Postby Roccosvega » Thu Nov 05, 2009 8:14 pm

This subject has been brought up before and because im using this rear I gained interest.
Scott (astre mutt)gave in my opinion the best Idea to accomplish the torque arm install
on this rear end.After taking it all in here's what I think is the easiest way to make it
happen. cut a piece of 4" channel to go from just behind the pinoin yoke to the driver
side axle tube.make 2 two piece clamps 1 for behind the pinoin yoke the other for the
axle.position the channel and weld one half of each clamp to the channel. Pipe of the
right size diameter with tabs having holes drilled in them for bolts was my thought.
then use small heavy gauge pipe cut and welded to the channel for the torque arm
bolt up.you might have to cut the 4" channel in two and weld together at the right
angle for torque arm bolt up.Im saying to use channel for strength but you can use
your Imagination. Anyway thats the vision astre mutt gave me.I know it will work.

Robert
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Re: 8.5" Rear modifications

Postby 80 MONZTA » Mon Mar 01, 2010 10:50 pm

Check out how this torque arm is connected, sure does look like a thin piece that sandwiches the cover. torque arm link
I am not going to copy it, just thought I would see what others thought about it.
RX7 torqe arm A.jpg
RX7 torqe arm A.jpg (44.33 KiB) Viewed 2423 times
RX7 torqe arm B.jpg
RX7 torqe arm B.jpg (38.88 KiB) Viewed 2423 times

I have a friend that can lazer cut up to 3/8" plate steel for me where he works. I wish it was 1/2", but maybe 3/8" will be thick enough. I have an idea of something that may work (thanks to the suggestions here), and I will make a pattern out of carboard and see if it looks strong enough before making it out of steel. Still a little too cold to work much, supposed to get all the way to 40 degrees this coming weekend :lol: Maybe I can get something done.
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Re: 8.5" Rear modifications

Postby Roccosvega » Tue Mar 02, 2010 5:15 pm

This set up is very good because it doesnt take up any extra ground clearence and strong under torque because it uses the 5 bolts and has that brace
over the top.The bolts on an 8.5's gussets would be on its lower cast flanges everything else stays the same. for an H Body you could eliminate the
four tubesteel braces going to the pivot point and just make a place to bolt the torque arm with hiem joints were the sock one usually is.I think
It would be bullet proof.

Robert
Last edited by Roccosvega on Tue Mar 02, 2010 9:09 pm, edited 2 times in total.
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Re: 8.5" Rear modifications

Postby cacmanjr » Tue Mar 02, 2010 8:24 pm

Nice but expensive.
bmr torque arm.jpg
bmr torque arm.jpg (27.54 KiB) Viewed 2384 times


Everybody hated this one.
bolt on torque arm.jpg
bolt on torque arm.jpg (12.26 KiB) Viewed 2384 times
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Re: 8.5" Rear modifications

Postby ROB » Fri Aug 27, 2010 5:34 pm

Bringing the topic back up.


cacmanjr wrote:Everybody hated this one.
bolt on torque arm.jpg


Why did "Everybody hate this one"? This looks usuable to me. Opinions?
Rob
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Re: 8.5" Rear modifications

Postby Rowdy Mclaughlin » Fri Aug 27, 2010 7:26 pm

Great topic, I like that RX7 mount
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Re: 8.5" Rear modifications

Postby cacmanjr » Fri Aug 27, 2010 10:07 pm

ROB wrote:Bringing the topic back up.


cacmanjr wrote:Everybody hated this one.
bolt on torque arm.jpg


Why did "Everybody hate this one"? This looks usuable to me. Opinions?
Rob


It is kind of a copy of the GNX set up. Most said the bolts would be in shear and they did not like that. The other opinion was that the torque arm would be better off if closer to the center of the rear end. I still have this set up if you are interested in it. I sold my 8.5 so I have no use for it at this point.
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Re: 8.5" Rear modifications

Postby 80 MONZTA » Sat Aug 28, 2010 12:16 am

My friend had this (below) laser cut out of 3/8" steel for me.
8.5 Rear mods A.jpg
8.5 Rear mods A.jpg (87.57 KiB) Viewed 2031 times

Unfortunatley, it somehow ended up being 3/4" off. :bang:
With the gasket you can see where it is messed up, so back to the programer to adjust it. So it will probably be a while before I get it back. I have not exactley figured out how to attach it to the torque arm. It will be similar to the BMR one above (but in conventional location, not under the driveshaft), just one side of course, and maybe using some of the webbing also.
8.5 Rear mods B.jpg
8.5 Rear mods B.jpg (92.66 KiB) Viewed 2031 times

I ordered solid rod ends, a double adjuster and bungs from Sphon so I can make my own torque arm from some 1.25" x .120 wall D.O.M. tubing.
8.5 Rear mods C.jpg
8.5 Rear mods C.jpg (99.48 KiB) Viewed 2031 times

Something like how my torque arm will look like below.
Spohn TA.jpg
Spohn TA.jpg (49.1 KiB) Viewed 2031 times
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Re: 8.5" Rear modifications

Postby 80 MONZTA » Sun Mar 25, 2012 10:08 am

OK, getting back to this. New place I work at has a tracing plasma cutter. Not CNC, but simply traces lines drawn out on paper, making things much easier for me. Here is the new part with just two holes drilled for mock-up, I will get around to drilling the other eight holes sooner or later. :P
8.5 Rear mods D.JPG
8.5 Rear mods D.JPG (110.84 KiB) Viewed 1616 times

And here it is sandwiched in place. The ears have some extra size to them that will be trimmed down after the rest is built.
8.5 Rear mods E.JPG
8.5 Rear mods E.JPG (102.14 KiB) Viewed 1616 times
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