i have a '71 454 with a 12 bolt open geared rear end. i want to convert it to positraction. i am unsure as to the gearing of the current rear, but assume it to be somewhat low because i get reasonable fuel economy and the car doesn't jump off the line like it had a 4:11 rear. as such, i'm guessing it's probably a 2:73 or there abouts. (i do not have any idea what the standard rear was in 1971 for an el camino configured with an LS5).

the question is this: assuming i wish to retain the current gears, exactly what do i need to change out (other than the obvious, the posi unit)?? can i use the original axles? are the ring and pinion gears different for an open rear vs. a posi rear. is it a #2 or #3 posi (assuming it's a ratio of 2:73)?? assuming it in fact is a 2:73 or there abouts, is there anything to be really gained by going up to a 3:08 gearing? while i can't swear to the accuracy of my speedometer, it appears that i am turning about 3000 RPM at about 80 mph. and about 1500 RPM at approximately 45mph.

thanks for the help

Chuck Hanson and crew just did this project on their Horsepower TV show Sunday, Feb. 15. Seems like they just stuck the posi unit in there, and retained all the original gears, axles, etc. Too bad you didn't see the show! It looked pretty simple! :D

wrencher

you got that right!! sorry i missed it for sure. perhaps i can try to find out if it will be rerun anytime soon.
many thanks for the heads up. it's greatly appreciated.

Lots of people use a device like this

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=2006&prmenbr=361

Search the web for more info to see if it would be right for you.

The put in a PowerTrax on Horsepower TV. I was thinking the Posi like Eaton needed to be 3.08 or higher...could be wrong though if can be lower. Check your ring gear and pinion mine was 3.08 open.

Rob

If it were me I'd go with the Eaton.

I wonder how strong that PowerTrax is in a drag race environment compared to a conventional Positraction with friction clutches. Does anyone have any idea?

I wonder how strong that PowerTrax is in a drag race environment compared to a conventional Positraction with friction clutches. Does anyone have any idea?

I suppose opinions vary. According to Super Chevy its better than a conventional Posi unit. Their article convenced me to get one for my 80 and sometime down the road I'll put one in my 76 also. The power Trax has no disk packs that can slip or need replacing over time and it doesn't require any special "Posi Fluid" for the rear end. Its a piece of cake to install don't have to remove any gears other than the old spider gears.

Before:

http://www.angelfire.com/tx4/Warped/80_elky_files/images/80_elky_rear_openb.jpg

After:
http://www.angelfire.com/tx4/Warped/80_elky_files/images/80_frame_rear_large.jpg

I also installed a new set of 4.10:1 Richmond Gears and generally rebuilt the rear end. But the PowerTrax was about 20 minutes of the total time. Like I said piece of cake.

Very nice. But have you really abused that bad boy yet? Make a few drag strip launches and see what happens and if it holds up then it would be a quick and easy way to get posi in an open rear end. By the way the pictures of your vehicle show a me good workmanship and detail.

No, I haven't gotten close to even the street yet, not with the 80. I have two problems 1 is Money, 2 is I keep spending some of the 80's cash on stuff to improve the 76. It always was a long-term project. :D

Thanks for the complements. I don't think it will be a concourse ride even the first show, I could be wrong, it is actually being built for my Wife. It has a 355 and a 700R4 4.11:1 power "everything that opens." It should crank out between 420 to 500 depending on if I decide to change the cam before or after. I plan on changing over to Solid Rollers and a very nice Cam. it has Pentrox Super Coil and Flame Thrower E-Module Accel Billet Distributor and any shinny stuff I can find or dream up on the engine.
I've got Chevy BowTie bolts holding the engine together. Logo Polished Wire Looms, I've contemplated painting the Air Gap Intake the same color as the engine/transmission which is the same color as that frame. Her belly is peach!

If it makes it through the 1/4 in the 8-low 9s I'll be happy. I look for that PowerTrax to hook up and if it happens, tear up that little 7.5" Ring gear. I have had lots of people tell me I would and some that I tend to trust well tell me its fine and should be able to deal with the power considering the fact that its an Auto not a standard. I live 10 minutes from the local drag strip.

Well that sure sounds like a fine 1980 Elky with all the good stuff. I don't think that a 7.5" rear end is going to last too long with all that power. With a 4.11 gear set and a 700R trans it should launch real hard.
By the way who's belly is peach--the Elky or your wifes?

Yee Haa Pete, some hole shot 4sure! 9's in the quarter, hmmmm, I hope you got your helmet on 8O

Nice pics of the rear end. What's with the clamps on the exhaust pipes in the after pic?

ElkyPete, great pics, looks like your 80 Elky is well engineered and thought out, but that doesn't surprise me coming from you though. I'm planning on assembling and installing a Ford 9" rear in my 84, reason being because it will be 400+hp with a 4speed manual, I have found a place that sells 9" Ford housings set up for G-body GM's for $280+shipping. However I have an 85 Trans Am that I was considering installing a PowerTrax unit in and would like to hear from anyone that has installed one and had it for awhile how it's holding up. I have heard that the PowerTrax causes a racheting effect around corners when new, but overtime it subsides after break-in. Any ECC members currently using a PowerTrax unit, whats your evaluation?

I saw that, it deffinently looked easy to do, but it's pretty expensive.