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I have a 1985 El Camino. Just put a 350 with a 4 barrel in it. Would like to go with a posi traction rear. Any suggestions?
 

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1987 El Camino 305 Swap
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Can you use this with a 2.73 gear ratio? I have the stock open 2.73 in mine that I'm trying to make a daily driver so posi would be a nice upgrade but I also like the low rpm cruise speed.
 

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Can you use this with a 2.73 gear ratio? I have the stock open 2.73 in mine that I'm trying to make a daily driver so posi would be a nice upgrade but I also like the low rpm cruise speed.
No, this one will only work with the 3.23 and up gears and come with the package, I went with the 3.55's but I have a 4L60E overdrive and cruises around 80 at 2600-2700rpms. They do have a Tru-Trac that will work with a 2.73 but it's not cheap.


The drop from a 2.73 to a 3.23 won't be too bad for hwy rpm's and the kick in the backside from a stop will be noticeable! Only problem would be speedo correction. Mine was simple because of the Dakota digital dash. Good luck!

Joe
 

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I have a 1985 El Camino. Just put a 350 with a 4 barrel in it. Would like to go with a posi traction rear. Any suggestions?
I replaced my 229 v-6 and 350c transmission with a stout 355 and a TH350 I had the non posi rear end replaced with a posi unit and a 3:23 gear it is just about perfect because I split time on the highway and around the city. If I did not drive on the highway the 3:42 would have been my choice. If you have overdrive don't be afraid of the 3:73. this is real world not of a chart! I hope it helps.
 

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87 elcamino v6 4.3 t.b.i.
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Daily driver ? Would leave posi alone. Turning and parking/etc going to drastically change. Tires wear more readily too,but not bad,but noticeable difference if u take turns s hard. A lot of fun,I admit,choose carefully for daily driver.
 

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I respectfully disagree with the above; a factory style limited slip that’s set up well will be completely unnoticeable except when you need it. I’ve owned two different ‘79 Trans Ams (posi was standard on them) and they were great; no problem ever. My ‘68 GS was a factory Buick 2.93 posi, it was trouble free, and the 3.55 12bolt posi in it now is also trouble free. (My Camino is a 2.41 open, but doesn’t really need to be posi for what I do with it and its stock 305).
Patrick
 

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1987 GMC Caballero, 400 HP 350, Holley Sniper EFI, 200-4R
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I'm torturing my right rear tire, unintentionally. I need to switch to a posi-trac to reduce the tire spin. If I can't get traction now, a lower gear ratio is going to be tough on both tires.

Is there some reason why this unit only works with the lower gear ratio that bolts to it?
 

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Agree with the Eaton, had it behind the LS1/6 speed since 02' in what's referred to as a weak 7.5 rear. When backing up & turning hard , I do notice a little drag. Other that that, I can tell. Can blame it on tire wear either. If I need to make a really sharp U- turn , I can just use extra throttle. 😊
I first swapped from a 2.73 to 3.73 & posi with my TPI/5 speed just before my LS swap. Could noticeably feel the vehicle lift with throttle, not just from not spinning a tire.
Going to both a lower rear gear ratio AND in my case a double overdrive trans is really an all around performance with mpg improvement. Those with the 700r-4 & it's super low first and / or a looser torque convertor don't need as low of a rear gear ratio.

Not an expert on it, but there are differences in internals of differentials. The lower numbered gears have a larger pinion gear which is likely the fit difference.
 

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Daily driver ? Would leave posi alone. Turning and parking/etc going to drastically change. Tires wear more readily too,but not bad,but noticeable difference if u take turns s hard. A lot of fun,I admit,choose carefully for daily driver.
Maybe if you are talking a spool or locker, I have / have had posi-traction (limited slip is a better term) on many vehicles without these problems.
 
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The diameter of the ring gear doesn't change, just the number of teeth. The same would apply to the pinion gear that meshes with it. The physical size is limited by the size of the case. What changes are the pitch and number of teeth.
 

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87 elcamino v6 4.3 t.b.i.
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Maybe if you are talking a spool or locker, I have / have had posi-traction (limited slip is a better term) on many vehicles without these problems.
Hmmm, seems like im misunderstanding difference between posi/standard/ limited slip.....you say posi/limited same huh? I've read that elsewhere on forum. I did basic research on the web as to what basics are for gear ratios. Guess I should do same for the different types of differential. Spool and locker? I'm assuming that's "true"posi. Im Open to lessons.....
 

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All of GM’s terms ‘posi traction’, ‘posi’, etc. mean limited slip. Aftermarket options mix in ‘spools’ and ‘lockers’ which do clunk and ratchet.
Patrick
 

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Hmmm, seems like im misunderstanding difference between posi/standard/ limited slip.....you say posi/limited same huh? I've read that elsewhere on forum. I did basic research on the web as to what basics are for gear ratios. Guess I should do same for the different types of differential. Spool and locker? I'm assuming that's "true"posi. Im Open to lessons.....
Stock "performance option" for non-CA cars in '87 was 3.08 I believe, that's what mine had. Mine was an open diff though (one wheel peel, if you will). Spool is basically a solid chunk of steel coupling the rear axles together with ZERO slip. Posi / limited has LOTS of variations but do "limit" the amount of slip from side to side. SOME limited slips will make a little noise (mostly f*rd vehicles I have had), all will allow the outside tire to rotate at a different speed in a turn (I think I have that right, someone correct me if I am wrong). Lockers are generally for 4x4's, and are basically a spool you can disconnect, I have heard of them being used at the drag strip.


If you have a stock-ish 305 and a 4speed auto transmission, it would be hard to beat a 3.42 or 3.73. I went with 3.73 and a Detroit true trac in my Currie 9" for the Camino, using it with a mildly built 350 and 5speed manual. It gets out of it's own way REALLY well.

I was torn between that or the 3.42 but figured I wouldn't drive it enough for it to make any real difference.
 
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87 elcamino v6 4.3 t.b.i.
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Stock "performance option" for non-CA cars in '87 was 3.08 I believe, that's what mine had. Mine was an open diff though (one wheel peel, if you will). Spool is basically a solid chunk of steel coupling the rear axles together with ZERO slip. Posi / limited has LOTS of variations but do "limit" the amount of slip from side to side. SOME limited slips will make a little noise (mostly f*rd vehicles I have had), all will allow the outside tire to rotate at a different speed in a turn (I think I have that right, someone correct me if I am wrong). Lockers are generally for 4x4's, and are basically a spool you can disconnect, I have heard of them being used at the drag strip.


If you have a stock-ish 305 and a 4speed auto transmission, it would be hard to beat a 3.42 or 3.73. I went with 3.73 and a Detroit true trac in my Currie 9" for the Camino, using it with a mildly built 350 and 5speed manual. It gets out of it's own way REALLY well.

I was torn between that or the 3.42 but figured I wouldn't drive it enough for it to make any real difference.
Thanks,that's some real info there! Coul dnt have asked for better explanation,since I read like 6 long articles on gear ratios, I now have a good understanding of rears, and how to match with trans/engine. Sounds like a fun setup you have there,safe driving. And thank you.
 

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@HKDUP87 Robert runs Ford type 9 inch with a spool in the drag El Camino. I believe he has gears near 4.56:1 and around 4.10:1.
It goes into wide circles when we take it off and then around the trailer to park. Otherwise....... we "Do Not" want to see it going in circles. It's job is to go straight.
Tire Wheel Car Vehicle Hood
 
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