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gear changing in 7 /14 rearend
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Author:  DavidInClemmons [ Wed Mar 29, 2006 7:45 am ]
Post subject:  gear changing in 7 /14 rearend
i know i have brought this up before and i am still in contact with a couple of you experts but i wanted to put this on the forum. i am keeping my 7 1/4 rearend and putting in 4:10 gears. i have added modifications to the motor to raise the hp to around 200. i am not going to drive on the highway above 45 mph and i want to get a good time at farmington in may. i will be foot brake racing. any thoughts on what i am doing?
Author:  Charrlie_S [ Wed Mar 29, 2006 8:44 am ]
Post subject: 
Do you have a sure grip?
Author:  DavidInClemmons [ Wed Mar 29, 2006 9:02 am ]
Post subject:  sure grip
i do not know if i currently have a sure grip; i doubt it. but i am looking into something called a phantom locker. ever heard of it or any suggestions on sure gripping a 7 1/4? i can't seem to find a posi or sure grip aftermarket for the 7 1/4.
Author:  Charrlie_S [ Wed Mar 29, 2006 10:44 am ]
Post subject: 
To the best of my knowledge, there is no source for a SG for the 7 1/4, other then the original factory units, which were discontinued eons ago. There was just a complete 7 1/4 SG rear on E-bay a couple of days ago. I am not familiar with the phantom locker. Since you are going to 4.10's, I figure, you're going to beat on this. Without a SG, there is a good chance, you will break the spider gears. The 7 1/4 with a sure grip is a lot stronger then most people give them credit for, but the open rears only have two spider gears, and if you get one wheel spinning, all the power goes thru the spiders to one side gear. With the SG the power is split between all the spiders, and side gears, so each gear only has half the loading. I have run the 7 1/4 SG with good success, on a 13 sec drag car with slicks.
PS As far as I know there is not a SG available for the later Dacota PU's with the 7 1/4 that could be adapted in.
Author:  Lars [ Fri Mar 31, 2006 7:07 pm ]
Post subject: 
And to think I threw away a 7 1/4 SG a few years ago. :roll:
Author:  Charrlie_S [ Sat Apr 01, 2006 4:41 am ]
Post subject: 
Quote:
And to think I threw away a 7 1/4 SG a few years ago. :roll:
:cry: :cry: :cry: :cry: :cry:

They are quite rare. They will not bring a lot of money (most will change to a stronger rear), but for a fair price, there are always buyers. Don't ever throw one away. A 3.55-3.91 SG 7 1/4 behind a mild slant, works well for street/strip.
Author:  james longhurst [ Sat Apr 01, 2006 7:36 am ]
Post subject: 
charlie-
i have a 7 1/4 sure grip rear that is complete. i haven't torn it down, but i was wondering if these are clutch-type diffs and if so, are they rebuildable? any sources for parts? i thought a while back maybe i could use the diff in my LBP 7 1/4 axle and maybe swap in some 3.55 gears for my valiant. this is a total backburner project (until i get a garage!)

-james
Author:  Charrlie_S [ Sat Apr 01, 2006 3:30 pm ]
Post subject: 
Quote:
charlie-
i have a 7 1/4 sure grip rear that is complete. i haven't torn it down, but i was wondering if these are clutch-type diffs and if so, are they rebuildable? any sources for parts?

-james
The 7 1/4 SG units could be either clutch type or cone type. My 3.91 and 5.13 rears are clutch, and I have a cone type on the shelf. I don't know for sure, but I think they changed from clutch to cone the same time the other rears did. I don't know about current availability of the clutch kits. A few years ago Frank Mitchel had some at his usual rediculus prices. Last year I found a kit on E-bay, that I got for about $19.00 (I was the only bidder). I do have the part number for the kit, if you want to do a search.
Edit: I did a search on parts voice, and found a supply of the clutch kits at "Collectors Auto Supply". Have no idea on their pricing.
Author:  featherduster76 [ Sun Apr 02, 2006 8:41 am ]
Post subject: 
Charrlie_S wrote:
To the best of my knowledge, there is no source for a SG for the 7 1/4, other then the original factory units, which were discontinued eons ago. There was just a complete 7 1/4 SG rear on E-bay a couple of days ago. I am not familiar with the phantom locker. Since you are going to 4.10's, I figure, you're going to beat on this. Without a SG, there is a good chance, you will break the spider gears. The 7 1/4 with a sure grip is a lot stronger then most people give them credit for, but the open rears only have two spider gears, and if you get one wheel spinning, all the power goes thru the spiders to one side gear. With the SG the power is split between all the spiders, and side gears, so each gear only has half the loading. I have run the 7 1/4 SG with good success, on a 13 sec drag car with slicks.
PS As far as I know there is not a SG available for the later Dacota PU's with the 7 1/4 that could be adapted in.

How much power do you think that these SG 7.25's will handle????
Author:  Lars [ Sun Apr 02, 2006 11:35 am ]
Post subject: 
Quote:
charlie-
i have a 7 1/4 sure grip rear that is complete. i haven't torn it down, but i was wondering if these are clutch-type diffs and if so, are they rebuildable? any sources for parts? i thought a while back maybe i could use the diff in my LBP 7 1/4 axle and maybe swap in some 3.55 gears for my valiant. this is a total backburner project (until i get a garage!)

-james
Yeah, it was back when I was still storing all my stuff at my Dad's place, he wanted me to make room and I had to toss a lot of stuff I wanted to keep. Holley 2BBL, a Carter BBD, a 318 block that had no ridge at all, the 7 1/4 rear, it just goes on and on. :?
Author:  Charrlie_S [ Sun Apr 02, 2006 1:34 pm ]
Post subject: 
Quote:
How much power do you think that these SG 7.25's will handle????
Can't give you a HP figure, but before I changed to a 8 3/4, I was turning mid 13's in the quarter in the 3200 car. I have been running that same rear since 1974, with one rebuild. Bearings and clutch plates. Don't try it with a stick, it won't take the shock loads.
Author:  featherduster76 [ Mon Apr 03, 2006 1:06 pm ]
Post subject: 
Can't give you a HP figure, but before I changed to a 8 3/4, I was turning mid 13's in the quarter in the 3200 car. I have been running that same rear since 1974, with one rebuild. Bearings and clutch plates. Don't try it with a stick, it won't take the shock loads. (Charrlie_S)

Thats pretty impressive. What do you figure that slant was putting to the
axle hp wise?? Did you just switch to an 8 3/4 for piece of mind incase you decided to get heavier on the spray :twisted: :shock: ????
I been fooling mostly with 8 1/4 rears here latley cause of the rising prices
of 8 3/4 rears and parts to build them. 8 3/4's are nice if you can get a good deal on one and they handle loads of torque- even the 741 casting in my 318 powered '71 Twister hasn't let me down ever and it's a 4 speed. 8 1/4 sg's are nice too, and the sg units are much cheaper :D
However for my slant car I did locate a 7 1/4 sure-grip from a dart last saturday...hmmm the wheels are turnin (literally :shock: :D )
Author:  Charrlie_S [ Mon Apr 03, 2006 2:06 pm ]
Post subject: 
Quote:

Thats pretty impressive. What do you figure that slant was putting to the
axle hp wise?? Did you just switch to an 8 3/4 for piece of mind incase you decided to get heavier on the spray :twisted: :shock: ????
)
As far as horse power, the Et-Hp-MPH-Weight formulas, show anywhere from 250 to 318, depending on which formula. I changed to the 8 3/4 because I had one sitting here, and I found a good 3.91 SG chunk. The 7 1/4 has held up well, but with 1.76 50foot time, i figured I was pushing my luck. So I deceided to swap it out before it broke. I can use it in a lighter car, with less motor. It will probably go in my 66 Valiant.
PS: you can run the numbers, yourself. Weight with me: 3250 lbs, ET 13.16, MPH 97.55
Author:  featherduster76 [ Mon Apr 03, 2006 5:15 pm ]
Post subject: 
but with 1.76 50foot time (by Charrlie S)


:shock: :shock: :shock: :shock: :shock:
Author:  featherduster76 [ Fri Apr 21, 2006 10:16 pm ]
Post subject: 
Are the 7 1/4 rears any harder to change the gear set in than say an 8.25??? Will the sure-grip units for these only work in the housings that
they came in??? Meaning basically can I take my stock duster 7.25 peg-leg and swap the sg into it without switching the entire rear. I have the other rear complete but just am not sure if the sg will interchange into the
"open" housing/etc.. :?: Is gear removal the same on these 7 1/4's as most mopar differentials??? (Same?? If not help please! A friend of mine
looked at it and it kinda puzzled him as to the removal of it??? Suggestions??
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