Author Topic: Type of 3rd member  (Read 5175 times)

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Offline DCarr511

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Type of 3rd member
« on: June 11, 2006, 07:18:46 PM »
I am curious as to what type of 3rd member or carrier is preferred for running on the Salt or at Maxton for that matter if there is a difference.

An open diff, LSD unit or a spool ? This would be in a production class vehicle.


Also whats the highest gear ratio available for a 8.5" 10 bolt GM rear ?

Thanks,
   Duane

Offline Dynoroom

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This is going to be good
« Reply #1 on: June 11, 2006, 07:23:34 PM »
Duane, you will find that at Bonneville & El Mirage the fastest guys run......


whatever they want...and argue about what wrks best. Some are open, others locked, still others...well you get the idea. Now the bike guys.........
Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...

Offline DCarr511

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Type of 3rd member
« Reply #2 on: June 11, 2006, 08:41:05 PM »
Michael, Thanks ! At least that tells me, that none of those are dangerous and all will work. I have the Original Posi in it now so it will work for the time being. It is a 3 series w/ 3.73's right now. i want to make at least one run at Maxton the way it is now just for documentation and a baseline.
Then I'll make the gear change and take it out there again.

Once I get into a 2 series gear will that require a differant carrier ? And if so who carry's those ? I have never heard a 2 series from GM.



Thanks,
    Duane

Offline jimmy six

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« Reply #3 on: June 12, 2006, 02:05:38 AM »
If your car spins with a locked rear take it out...If it spins without one, put one in..If your a roadster at Bonneville it's not if, but when... :P . Long wheel base cars seem to like them locked up...Good Luck
First GMC 6 powered Fuel roadster over 200, with 2 red hats. Pit crew for Patrick Tone's Super Stock #49 Camaro

terry russell

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Type of 3rd member
« Reply #4 on: June 12, 2006, 02:12:37 PM »
Unless your eng. will turn 8000 rpms a 3.73 is to much. You might want to change to 3.25-3.00. With 3.73 I was at 5000 at1/4 mile and 3.42 5000 way before the 1/2. This was with a 28" tire .
good luck Terry

Offline DCarr511

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« Reply #5 on: June 12, 2006, 04:04:49 PM »
Quote from: terry russell
Unless your eng. will turn 8000 rpms a 3.73 is to much. You might want to change to 3.25-3.00. With 3.73 I was at 5000 at1/4 mile and 3.42 5000 way before the 1/2. This was with a 28" tire .
good luck Terry



Thanks for the info. I understand that is way to low of a gear to be running LSR with, but I want a baseline as the car came stock. Then I will change the rear gears to something in the 2's.  BTW Its a 1986 Monte Carlo SS. Its also got some miles and wear on it so I'm not expecting to much power or to high of speeds from it. Basically just a way to get started in LSR and an excuse to get away for a couple of weekends.

Randy Williams

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Re: Type of 3rd member
« Reply #6 on: June 16, 2006, 12:35:08 AM »
Quote from: DCarr511
I am curious as to what type of 3rd member or carrier is preferred for running on the Salt or at Maxton for that matter if there is a difference.

An open diff, LSD unit or a spool ? This would be in a production class vehicle.


Also whats the highest gear ratio available for a 8.5" 10 bolt GM rear ?

Thanks,
   Duane


Duane, While your changing your gear ratio,I might suggest that you install C-Clip eliminators or Ford style axles.

Offline jimmy six

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Type of 3rd member
« Reply #7 on: June 16, 2006, 10:08:06 AM »
D...The older 10 bolts were available up to 2.29. Don't know if that's the 8.5".
First GMC 6 powered Fuel roadster over 200, with 2 red hats. Pit crew for Patrick Tone's Super Stock #49 Camaro

Offline DCarr511

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Re: Type of 3rd member
« Reply #8 on: June 17, 2006, 03:40:49 PM »
Quote from: Randy Williams
While your changing your gear ratio,I might suggest that you install C-Clip eliminators or Ford style axles.


Thats an excellant suggestion Randy and one that will be used.


Quote
The older 10 bolts were available up to 2.29. Don't know if that's the 8.5".


I dont know much about them myself but will be researching it. I know the  7.5" has a 2.14 gear available and it was advised by by  friend and long time LSR Racer that I go to the 7.5" but I have concerns about it being able to hold up on an asphalt surface. ... Again thats something I will be looking into Thanks for the information !

I was hoping .. again to make it to Maxton next weekend thinking I had the time off of work .. but it again turns out not to be so. Now I am planning on  the Sept. meet. And the good news is that after watching the Worlds Fastest Indian for the uptinth time, my 17 yr. old son FINALLY has an interest in cars and LSR and is looking forward to going to Maxton. My Speed Week trip has alrady been planned so he cant make that ... but maybe next year. So with him showing some enthusiasim towards this, that makes for a bit more incentive for to go forward with this project.

Thanks again for all the info !!

Offline Sumner

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Re: Type of 3rd member
« Reply #9 on: June 17, 2006, 03:58:57 PM »
Quote from: DCarr511
Quote from: Randy Williams
While your changing your gear ratio,I might suggest that you install C-Clip eliminators or Ford style axles.


Thats an excellant suggestion Randy and one that will be used.


Quote
The older 10 bolts were available up to 2.29. Don't know if that's the 8.5".


I dont know much about them myself but will be researching it. I know the  7.5" has a 2.14 gear available and it was advised by by  friend and long time LSR Racer that I go to the 7.5" but I have concerns about it being able to hold up on an asphalt surface. ... Again thats something I will be looking into Thanks for the information !

I was hoping .. again to make it to Maxton next weekend thinking I had the time off of work .. but it again turns out not to be so. Now I am planning on  the Sept. meet. And the good news is that after watching the Worlds Fastest Indian for the uptinth time, my 17 yr. old son FINALLY has an interest in cars and LSR and is looking forward to going to Maxton. My Speed Week trip has alrady been planned so he cant make that ... but maybe next year. So with him showing some enthusiasim towards this, that makes for a bit more incentive for to go forward with this project.

Thanks again for all the info !!


Ok I hate to suggest this as it is another "belly button" idea (just kidding JD  :wink: ), but if you are going to install another rear I would go to the old reliable 9 inch Ford.  

You don't have to go the route of "c" clip eliminators (most of them leak on the street).  

You can have multiple gear sets that easily exchange back and forth between the track and the street without having to set them up each time.  

They are strong.  You can get parts to build them to any power level you want.

You can get 2.47 gears pretty easy.  With 2.47 gears and 28 inch tires you can run up to about 250 mph at 7500 rpm, which is not that high rpm for a race motor (for what you want to do 2.73's migh be a better gear, but use a [ Gear Calculator -- part way down ] to figure that out).  

c ya, Sum

Offline DCarr511

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« Reply #10 on: June 17, 2006, 09:07:17 PM »
Sumner ...  the Ford 9" was my original plan until I found out that some cars are making a whole lot more power than I will ever consider and going faster than I could ever imagine using the GM 7.5" 10b, but thats at the Salt and El Mirage.

And of all the diffs available I have always heard the 9" takes the most power to turn. And since I can buy complete 8.5", 8.2" or 7.5" GM 10b core for 100 $ that sounds like the thing to do. I want to pretty much be able to put this car back to original condition if I ever felt like it. I had a 64 Malibu SS that I owned for 19 yrs and took it from a bone stocker to a backhalved fiberglass covered drag car and at the end really regretted it and I dont want to needlessly destroy another car trying to have fun.

I know it will require a cage at 135 mph at Maxton and at any MPH for the Salt. So that will get put in when the time comes.

Thanks again for the info !! And if anyone else has anything to add please do so.

I dont do a lot of math and was curious if anyone knows of a chart online that you can guesstimate the HP needed to run a certain MPH based on frontal area and friction etc.

Offline Sumner

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Type of 3rd member
« Reply #11 on: June 17, 2006, 11:47:20 PM »
Quote from: DCarr511
Sumner ...  the Ford 9" was my original plan until I found out that some cars are making a whole lot more power than I will ever consider and going faster than I could ever imagine using the GM 7.5" 10b, but thats at the Salt and El Mirage.

And of all the diffs available I have always heard the 9" takes the most power to turn. And since I can buy complete 8.5", 8.2" or 7.5" GM 10b core for 100 $ that sounds like the thing to do. I want to pretty much be able to put this car back to original condition if I ever felt like it. I had a 64 Malibu SS that I owned for 19 yrs and took it from a bone stocker to a backhalved fiberglass covered drag car and at the end really regretted it and I dont want to needlessly destroy another car trying to have fun.

I know it will require a cage at 135 mph at Maxton and at any MPH for the Salt. So that will get put in when the time comes.

Thanks again for the info !! And if anyone else has anything to add please do so.

I dont do a lot of math and was curious if anyone knows of a chart online that you can guesstimate the HP needed to run a certain MPH based on frontal area and friction etc.


I understand on where you are coming from, but I've looked at the same deal for my pickup since eventually I want to run it on the salt.  I'm not sure if you are aware of some of the problems with the  c-clip eliminators or not.  Most of the cheaper ones have real sealing problems and just don't seal on a street car.  I finally figured if I went that way I would get the ones where you have the ends of the axle tubes cut off and then you can run ford seals and bearings.  I don't know about maxton, but to run on the salt you have to have them if you don't have a ford type rear regardless of speed.  Now if you ran say the 130 mph club in Sept. on the salt you might not need them.

To me by the time I went to the trouble of putting the ends on the axle tubes and new axles I my as well go to a Ford rear-end.  I also lucked out and traded peaches and other fruit (I didn't want to pick anyway) from my old orchard to a guy for 3 ford 9 inch rearends one summer.

I agree that for modest hp you don't need the stronger rear on the salt due to the traction there.  At Maxton it would ease your mind a little.  If you look and wheel and deal a little you could probably find a ford and just rebuild it if it was the right width.  You would have to put on spring mounts and need another driveshaft, but still you might be able to do the whole thing for under $500.  Keep the present one to go back to stock.

The formulas you want might be on those links on my site down at the bottom with the "Aerodynamics Related Sites".  Look at the "Aerodynamic and Rolling Horsepower Calculations By Bowling & Grippo ".

c ya, Sum

Offline DCarr511

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« Reply #12 on: June 18, 2006, 11:17:24 AM »
Sumner.. Ya I plan on buying another rear and changing the ends on it to the Ford Style. I have a rear end jig so that wont be a big issue. And having something that bolts right in and will work is always a good thing.

And if the 9" takes more power to turn over, thats something that will be lost as long as that rear is in the car, changing housing ends will be a one time deal. Since it looks like I can get a 2.41 or 2.73 gear for the 8.5, thats going to be my choice since I have no doubt that they will hold up on pavement to the power I'll be making. I'll stuff it full of the good parts, axles, carrier, yoke and such.