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Rear end choice


FESTER60

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I installed a '96 Mustang Cobra 8.8-inch rear end in my '47 P-15. The width from WMS to WMS is nearly identical to the Plymouth and the bolt pattern is the same. It has a 3:27 ratio with traction lock and huge disc brakes. I put it behind a 360/727 and used the Mustang driveline with a combo joint to match up to the Mopar yoke. I had to grind a lot of extraneous stuff off the rear end housing and weld on a pair of spring perches to fit the original leaf springs. This conversion requires at least one-inch lowering blocks; without them the emergency brake return springs would conflict with the leaf spring.

I have somewhat smaller disc brakes on the front, so to avoid prematurely locking up the big rear discs, I installed a proportioning valve in the line to the M/C. Other similar year non-Cobra Mustangs would have rear ends with smaller brakes.

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I like the disk brakes, and they're very stout. The Exploder rear is supposed to be much stouter than the 8.8" Ranger, from what I've heard. I've heard some folks says they're about as strond as a 9".

Again, the main reason I picked one up was the disk brakes. I almost grabbed an 8 1/4" Cherokee instead. If it'd had disk, I'd done it to keep it Mopar...haha!

One other minor nuisance is they use 3 1/4" u-bolts instead of 3"...wide housing.

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lot of folks here looking to upgrade the axle don't take everything in consideration in first choice to change..working all the formulas and "paper racing" will put one way ahead and further down the road for less out of pocket expense..some are building their cars to drive today with the stock 6 and 3 on tree but also have plans to do other upgrades along the way..that is why I mentioned the style of rear axle is consideration of best type to use overall for the total end product..the banjo design is the best choice for these applications and will allow quick change of rear gear ratio and as we all know these pumpkins are easy to come by at most all swap meets. The banjo style has been around for many years and about every manufactuerer has used them at one time or another including the foriegn makers...I know the Ford has the 9 and 8 inch banjo..our old cars are stock banjo but with few ratio selections, Mopar 8 3/4 are banjo and the list goes on..unless you really planning on ripping up the asphalt with big power V8 there is little need to be greatly concerned about the ring gear diameter..the input shaft on the pinion is your prime concern..magazine article like to always overbuild and usually pushing max HP out and thus the trend to say the ford 9 or the mope 8 3/4 are the better units..for that application rightly so..but for these old cars with 110 HP, nah...having to have a Ford 9 is overkill UNLESS like mentioned earlier..your plans down the road are for a bigger engine..these applications also are the factor that puts these axles at a high price to start with..and will also be the ensuring factor that parts for rebuild will be available..but the average grunt car today is not getting these axles....cost have put the other style more in the mainstream..so just saying be sure of what you intend to have as an end product when selecting the axle to swap today..

the Ford 8.8 axle today is the 9.0 of yesterday..the MoPar 8 1/4 is basically the backbone of the rear wheel drive suv/trucks..gear sets are available..but the work to change and set up is quite involved..usually easier to swap the entire axle..

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Lots to consider. I will be using my stock wheels and have a 318/904 for power. I will have a disc conversion on the front and would like to have discs on the rear as well. Maybe I will give the Explorer rear a good look. Seems to be a popular choice.

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Well I located an Explorer rear from a 99 not too far from my place. Only 109K on it. 3.55 ratio. I think I can get it for around $100. Does this sound like a decent deal? I am kind of ignorant about the whole rear end thing. A real learning curve for me on this one.

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741...1 3/8 diameter pinion..medium range gear strength..oh it will take about all you want to give it from a production machine including a few 413's out there driving these suckers..just installed one of these in my current project, the bz cp with 3.23 gears..741 replaced the 488 I think it was and used through 1973 I believe when it was replaced by the larger pinion common to the 742 casting..last of the 8 3/4's..

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FESTER60; not sure about what "price" is right. I would think $100.00 is not a bad deal for a "good" rearend, esp. if it's right for your app. I gave $150.00 and have seen them priced in the $250.00 range?? TIm Adams; does the 295 number on the side of my 8.75 rearend casing indicate the "ring-pinion" ratio?? :confused: Cass, alias littlemo...

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I think this 8.75, 741 rearend is a 2.95 ?? Am I reading the casting #'s correctly ?? :confused: Cass, alias littlemo...

It looks like that is the what you have. From the web.

Gear Ratio and Sure-Grip Identification:

Through 1965, the factory ratio was stamped on the identification boss, followed by an 'S' if it had a Sure Grip. After 1965, a tag was affixed under one of the carrier mounting nuts to identify the ratio. If it had a Sure Grip, an additional Sure Grip lube tag was sometimes added. Later year versions sometimes had the filler plug painted orange.

http://www.dippy.org/forum2/index.php?topic=84.0

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No..that is not how they were made..that casting is not relevant to gear ratio..as for the closest gear to that number is the actual 2.94...as stated..the later models had the ratio on a tag under a nut..earlier stamped with a set of metal stencils as the original P15 and up rear gears were ..the 57 through 64 were taper axle 8 3/4 and had a 488 case I think...not something that is highly sought after..the 741 is strong for about any street application you want..the 742 is the heavier input shaft..all interchange in the housing as I have read...I check for that casting number on my but it is a 742 rear chunk and thus the numbers are all different..I may have a 741 under the van with I know is 3.23 gears just have not been that curious to look..

the only way to check your ratio is to spin the input rev's to one wheel rev..and then that is a bit hard to do as you have to know the year axle and gears available for that year..given it is still stock..best way is to pull the hog and count pinion and ring and do a bit of division...for instance..42 tooth ring gear divided by 13 tooth pinion is 3.23

if you go to a yard and pull a axle..and if that car was ever raced or modified for the street..you still guessing to the gears..

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Just slightly OT here but what gear ratio would be most desireable for a stock P15 wanting to be able to cruise at 65 without straining engine.

I've got a 3.73 in mine and have done 65. With my radials I believe I calculated 65 at 3000 RPM. I think you could go a little lower like a 3:54 but anything lower than that and I think you'd have trouble starting out.

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