beef up stock 8 inch diff? - Vintage Mustang Forums
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post #1 of 53 (permalink) Old 09-08-2019, 01:54 AM Thread Starter
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beef up stock 8 inch diff?

I have a 408whp/440tq(just Dynod) 347 in a 65 convertible mustang with a stock t5. I can't get traction in first at all with my bfg 215/60r15's so I'm getting some M/T ET Street SS 235/60r15 radial's. I currently have the stock open diff(with some steeper gears my dad put in for towing the boat, I think 3.31?). I was thinking about putting this in:
https://www.currieenterprises.com/ce-5018
Anything else I should do? (besides look for a 9 inch which might not be needed for this hp/tq)
I do want to take it to the track sometime but don't have a roll bar etc-so it might be a one time just for fun thing

Last edited by Chip Phillips; 09-08-2019 at 01:56 AM.
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post #2 of 53 (permalink) Old 09-08-2019, 06:05 AM
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You would be better off upgrading to a nine inch housing and 31 spline axles. What cylinder heads, Intake, Cam and Carb are you using in your 347?
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post #3 of 53 (permalink) Old 09-08-2019, 07:44 AM
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https://www.ebay.com/usr/tj1141?_trk...88.m1543.l2754
You'll break the T-5 before the 8"


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post #4 of 53 (permalink) Old 09-08-2019, 08:07 AM
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I've read at-length articles that the 8" can be just as sturdy as a 9" unless you just had to have big-journal bearings and 31 spline, maybe with a spool for drag etc. I have pounded the $h!+ out of some 8s and never broke one, but I've broken a couple of u-joints and a trans mount.

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post #5 of 53 (permalink) Old 09-08-2019, 08:33 AM
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Which T-5 do you have, the stock GT Mustang one or the Cobra T5z spec'd one? The first gear ratio for a stock GT Mustang sucks as it is way too low. Regardless with a single leg rear end traction will be an issue. I was fortunate to find an 8" Traction Lok in a bone yard years ago. It has held up to plenty of abuse. I have heard good things about the new style Detroit locker that you posted. I see Traction Lok 8" units are available for a little less. https://www.quickperformance.com/For...t_p_16014.html

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post #6 of 53 (permalink) Old 09-08-2019, 09:27 AM
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I was told by TJ's auto that the later model third member is stronger. He would not rebuild the early 8 inch. Ford Rears 8 inch 9 inch Posi Traction Rear Differentials
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post #7 of 53 (permalink) Old 09-08-2019, 09:28 AM
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The tru trac is a great choice--whether you go 8" or 9". Also would beef up the drive shaft and u-joints and consider cal tracs.
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Last edited by JimGTA; 09-08-2019 at 09:32 AM.
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post #8 of 53 (permalink) Old 09-08-2019, 10:32 AM
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I think your rear gear is good and a true track is a good choice.
But as mentioned previously, you’ll break the T5 before you break the 8 inch.

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post #9 of 53 (permalink) Old 09-08-2019, 10:39 AM
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Yup. That T-5's a goner with slicks...... or DOT "slicks"
(high HP, slicks and missed shifts are the kryptonite for that trans)
Never broken an 8" diff. I've broken leaf spring segments, u-joints, engine mounts, etc. though.
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post #10 of 53 (permalink) Old 09-08-2019, 10:52 AM
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I've got a T5 behind my 408 stroker, typically flog the dogsh*t out of it, and it's held up just fine. As for your rear end, look into the Explorer swap. It's an easy was to swap in not only a double legger, but better gears AND disc brakes. Best part is, they're fairly cheap to obtain!

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post #11 of 53 (permalink) Old 09-08-2019, 12:48 PM
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I've got an 8in with Dutchman axles, a trak lok and 3.55's within the later '67 case. It lives behind my 420hp 331 and t5z on the street with 225/60r15's.
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post #12 of 53 (permalink) Old 09-08-2019, 12:58 PM
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You will destroy that whole drivetrain once you start to hook. I speak from experience .
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post #13 of 53 (permalink) Old 09-08-2019, 01:03 PM
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Quote:
Originally Posted by gt350sr View Post
I've got a T5 behind my 408 stroker, typically flog the dogsh*t out of it, and it's held up just fine. As for your rear end, look into the Explorer swap. It's an easy was to swap in not only a double legger, but better gears AND disc brakes. Best part is, they're fairly cheap to obtain!
Interesting, what tires are you running on the rear?

t
t



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post #14 of 53 (permalink) Old 09-08-2019, 01:04 PM
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Yeah it’s really all about the traction. If it’s sticking a loading properly things will start to break.
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post #15 of 53 (permalink) Old 09-08-2019, 03:17 PM
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Quote:
Originally Posted by 2nd 66 View Post
Has anyone bought from Alan since he took over for TJ? I don’t have experience from either but was planning on buying from TJ based on feedback here. I saw following the link today that TJ has passed away, and Alan has taken over the operation (per the eBay page).

James

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