Fox T-Bird/Cougar Forums

Technical => Drivetrain Tech => Topic started by: bryan163 on June 19, 2012, 03:36:31 AM

Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 19, 2012, 03:36:31 AM
The last few months 7.5" rear end has been getting noisy. So I went ahead and ordered a new set of 3.45 gears to replace the current 3.55. When I opened the cover I was surprised to find a ford Trac Lok limited slip. I was expecting to find a gear locker because thats what I asked for years ago when I last had the rear end built. The gears were Richmond 3.55 like I requested.
The problem is that some of the ears are broken on the clutch plates. I want to rebuild my LSD carrier with some new clutches, but I cant find the parts anywhere:punchballs: Does anyone know where to get clutches for a  7.5" ford Trac lok?

This is the new gear set
http://www.jegs.com/i/JEGS+Performance+Products/555/60021K/10002/-1 (http://"http://www.jegs.com/i/JEGS+Performance+Products/555/60021K/10002/-1")
(http://www.jegs.com/images/photos/500/555/555-60001K.jpg)
(http://sphotos.xx.fbcdn.net/hphotos-snc6/224994_10151200143498222_1892007148_n.jpg)
(http://sphotos.xx.fbcdn.net/hphotos-prn1/538644_10151200436758222_962711243_n.jpg)
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 19, 2012, 06:46:40 AM
Here you GO!!!

http://www.latemodelrestoration.com/item/YPK-F75-PC/79-04-Mustang-75-Trac-Lok-Clutch-Kit
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 19, 2012, 10:34:53 AM
Thats exactly what I need, but it says " out of stock".
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 19, 2012, 12:28:14 PM
http://www.ringpinion.com/DiffWizard.aspx
Title: 7.5 Rear rebuild and gear swap
Post by: V8Demon on June 19, 2012, 01:59:48 PM
Ummmmm....  Never heard of a 3.55 gearset for a 7.5" rear before....

3.45 yes.  Not 3.55...
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 19, 2012, 03:57:17 PM
Maybe they were 3.45, but I'm pretty sure I saw some 3.55 sets when i was shopping for these. I was just counting the rotations and it was about 3.5 turns of the pinion to one turn of the axle. Not the most accurate test. Anyway, I found my clutches today at the ford dealer right down the street. They had them in stock for $103 :)
Those little ears on the clutch discs are what were breaking off on the old clutches.
(http://[IMG]http://i663.photobucket.com/albums/uu352/bryan163photobucket/2012-06-19_15-43-32_459.jpg)[/IMG]
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 19, 2012, 07:38:56 PM
As far as i know their is no 3.5 final in a 7.5 but who cares. Glad you got the parts you needed.
Title: 7.5 Rear rebuild and gear swap
Post by: EFFalcon on June 19, 2012, 08:08:23 PM
so your running the combo in your sig through a 7.5?

maybe i won't need to upgrade afterall :D
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 19, 2012, 09:57:40 PM
The 7.5 is no slouch. It can handle some good ponies if set up correctly
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 20, 2012, 01:08:15 AM
I do beat on this car pretty hard. With all the towing, racing, and drifting. I used to tow an 1800lb trailer regularly with 3 quads. I'm still waiting on my gears and bearings to come in. Tracking says tomorrow. Here's some more pics.
look at the bent, dislocated ears sticking out of the clutch pack. I bet that was my noise.
(http://i663.photobucket.com/albums/uu352/bryan163photobucket/2012-06-19_21-18-28_857.jpg)
you can see the bent clutch ears wrapping around the side gear here.
(http://i663.photobucket.com/albums/uu352/bryan163photobucket/2012-06-19_21-49-40_992.jpg)
some smoked disks
(http://i663.photobucket.com/albums/uu352/bryan163photobucket/2012-06-19_21-51-17_157.jpg)
(http://i663.photobucket.com/albums/uu352/bryan163photobucket/2012-06-19_21-51-17_157.jpg)
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 20, 2012, 05:59:03 AM
In all the years in this business i have never seen a posi unit burn clutches like that,  I think it is time to stop DRIFTING. That unit shows TREMENDOUS FRICTION AND HEAT ISSUES. It tells me the unit is trying to do it's job of keeping power to both wheels and it CANT. If i may!!!! If you keep on DRIFTING i would suggest an OPEN REAR!!! Personally my view on drifting is that is is the DUMBEST THING I HAVE EVER SEEN ANYONE DO WITH AN AUTOMOBILE!!! Just me could be wrong!!!
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 20, 2012, 06:04:51 AM
kk
Title: 7.5 Rear rebuild and gear swap
Post by: V8Demon on June 20, 2012, 08:56:40 AM
Quote
If you keep on DRIFTING i would suggest an OPEN REAR!!!

I'm not a fan of drifting myself, but that would be a step in the wrong direction.... A lot of the drifters will step up to a spool....
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on June 20, 2012, 05:10:47 PM
Quote from: V8Demon;392836
I'm not a fan of drifting myself, but that would be a step in the wrong direction.... A lot of the drifters will step up to a spool....


Now that is something to catch my fancy. Lets put a spool in a street car. This is a street car we are talking about am i correct??? If it was just used for drifting a spool would be fine. But that posi unit is clearly destroyed i would say. Just me could be wrong again!!
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 20, 2012, 07:56:55 PM
I should point out that the clutch pack on the other side was still in great shape. I'm pretty shure the transmission shop that built my rear screwed it up when they assembled it. The unit should not be able to generate enough friction to bend those ears out of their pockets in the carrier.
I counted the teeth on the old gear set and divided to find out the old ratio was 4.10, not 3.55. The shop really didnt do anything I asked them to. So not hard to believe they would screw up on the assembly.
Tom, most drifters actually agree that drifting is the stupidest thing you can do with a car, but its so much  fun that we just cant resist. Open diffs are no good because both wheels have to spin all the time and predictably for the car to slide consistantly.
I just finished re-assembling the carrier with the new clutches. I'll post some pictures later when I get home. One of my friends is hopefully gonna be stopping by to help my set up the ring and pinion tomorrow.
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 20, 2012, 10:32:21 PM
(http://sphotos.xx.fbcdn.net/hphotos-prn1/545448_10151204382428222_366514262_n.jpg)
(http://sphotos.xx.fbcdn.net/hphotos-ash3/579963_10151204383093222_1786061888_n.jpg)
Title: 7.5 Rear rebuild and gear swap
Post by: Chrome on June 23, 2012, 03:37:50 AM
Drifting with open rear not quite possible. With all that u put this thing through, I believe you need something a little more stout than factory limited slip. Spool would be killer, but u would loose all street driveablity. I would use a Detroit Locker or something like it. Try looking into off road magazines or sites for rear end. 7.5 is pretty tough, but you may need to step up to an 8.8 or possibly a 9.
Title: 7.5 Rear rebuild and gear swap
Post by: Chrome on June 23, 2012, 03:52:57 AM
Quote from: TOM Renzo;392825
In all the years in this business i have never seen a posi unit burn clutches like that,  I think it is time to stop DRIFTING. That unit shows TREMENDOUS FRICTION AND HEAT ISSUES. It tells me the unit is trying to do it's job of keeping power to both wheels and it CANT. If i may!!!! If you keep on DRIFTING i would suggest an OPEN REAR!!! Personally my view on drifting is that is is the DUMBEST THING I HAVE EVER SEEN ANYONE DO WITH AN AUTOMOBILE!!! Just me could be wrong!!!
I myself would not put my car through that. I do, however, support the OP in his endevors. American muscle kick'n tail in a ricer sport.... Gotta love it! Must be a lot of fun as well.
Title: 7.5 Rear rebuild and gear swap
Post by: BadShoe on June 23, 2012, 11:30:04 AM
I doubt the carrier/clutches were setup wrong. I see it was the right pack which as in drag racing is more likely to spin more. I've seen damaged fibers many times (mostly in trucks that get stuck alot). In a drifter car, I think you'll be doing this again, more often since it's a light duty 7.5".
Title: 7.5 Rear rebuild and gear swap
Post by: 1BadBird on June 23, 2012, 01:53:00 PM
I see that the clutch plates are dry. I might suggest, If you didn't do it, is to remove them and pre-soak them in a mixture of the oil N friction modifier.

A Detroit locker or a Torsen dif would be a good choice for ya. I don't know about the availability for ur 7.5 though. Do I see a 8.8 in your future??
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on June 23, 2012, 10:29:45 PM
Quote from: Chrome;393058
I myself would not put my car through that. I do, however, support the OP in his endevors. American muscle kick'n tail in a ricer sport.... Gotta love it! Must be a lot of fun as well.
Thanks for the support. It was supposed to be built with a locker originally. I don't know why the shop used the trac-lok. I did configure it more aggressively this time with a friction disc between every steel instead of the stock configuration where there were two steels butted together, only making use of one side of those two clutches. I also placed one of my old steels before the shims so the outside of the last clutch disc is being used instead of spinning against a shim, which would have just spun too.
Most guys are running spools or welded diffs, but I drive my car almost every day. It's still my grocery getter and daily commuter. The LSD hasn't let me down yet. Even with those bent clutches it was still burning both tires:)
I know drifting is hard on the car, but I think I enjoy the challenge of finding the weak links and building it stronger. I would get bored if I didn't always have something to work on.

Quote from: 1BadBird;393088
I see that the clutch plates are dry. I might suggest, If you didn't do it, is to remove them and pre-soak them in a mixture of the oil N friction modifier.

A Detroit locker or a Torsen dif would be a good choice for ya. I don't know about the availability for ur 7.5 though. Do I see a 8.8 in your future??
After seeing how easy it is to pull the rear end I may swap in an 8.8 from a turbo coupe if the right deal comes along. There are definitely a lot more parts available for an 8.8. Very few options for the 7.5. I will do the pre-soak too. thanks for the tip. I pressed the new bearing onto the pinion gear last night after freezing the pinion and heating the bearing, I pounded It down with a piece of 2" exhaust tubing and a small sledge hammer. went on nice and easy. I'm supposed to be waiting for some help from a friend to set up the gears, but if he's not there before monday I'm just gonna do it myself.
Title: 7.5 Rear rebuild and gear swap
Post by: V8Demon on June 23, 2012, 11:58:36 PM
Quote from: TOM Renzo;392872
Now that is something to catch my fancy. Lets put a spool in a street car. This is a street car we are talking about am i correct??? If it was just used for drifting a spool would be fine. But that posi unit is clearly destroyed i would say. Just me could be wrong again!!


I said a lot of them did it.  Where did I recommend that he do the same?

Quote
Drifting with open rear not quite possible.

THIS is the point I was driving at.  An open diff would be a step in the wrong direction. 

If it were me using my car for the same purpose as the OP?  Torsen diff....
I think a Detroit Locker would be less predictable then the Torsen in a drifting situation.  The Powertrax Lock right (another full locking diff) is a little easier to figure out in my experience between the two.  I have the Detroit in the Stang and the Powertrax in the Cougar.

Basically anything to get rid of the spider gears and clutch plates.
Title: 7.5 Rear rebuild and gear swap
Post by: Haystack on June 24, 2012, 12:34:00 AM
You can get an open rear sideways, but you can also pull the tire off of the rim in a slide. I did that a time or two showing off back in my high school days.

My vic has a locking 3.55 8.8"s rear axle, and gets sideways quite easily in light rain. If I excelerate around a corner, even lightly, the tail will kick out and I can hold it for a bit. As soon as the tires grab though, it goes which ever direction the front tires are pointed, so it will snap very hard if I'm not on top of it. It has needed tires for a while though. It expires this month, and I was surprised when they passed last year.
Title: 7.5 Rear rebuild and gear swap
Post by: 1BadBird on June 24, 2012, 11:17:23 AM
Quote from: bryan163;393117
a friction disc between every steel instead of the stock configuration where there were two steels butted together, only making use of one side of those two clutches. I also placed one of my old steels before the shims so the outside of the last clutch disc is being used instead of spinning against a shim, which would have just spun too.

Uhhhhh. I've never seen a stock configuration where it was 2 steels butted together. That IMO is where that shop messed up big time by doing that. I used to work with a guy that live next door to me that built rear ends for a living and we NEVER did that. We built them for drag, off road, circle track, street.


Quote from: bryan163;393117
I will do the pre-soak too. thanks for the tip.

Any time. Another little tip for ya, get the old pinion bearing removed and take a barrel sanding roll and lightly sand the inside of the old bearing till it slides easily over the old pinion shaft. That makes it way easier to check the pinion depth and to make the required shim changes.
Also, when/if you swap to a 8.8 and it has a LSD, you can get carbon fiber discs for it. That's what's in my Cobra 03'  IRS diff.
Hope all goes well.

John
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on July 04, 2012, 01:16:08 PM
Update: I finally got around to putting my axle back in the car last night after work. I'm really liking the 3.45 gears a lot better than the 4.10s that i took out. I was worried that I would miss the low end grunt, but somehow it doesn't feel any less powerful off the line and now I can go faster on the top end :) The LSD is working great too. So glad I got it ready in time for the 4th!
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on July 04, 2012, 08:22:28 PM
Now keep it off those SLIDER TRACKS and give it a break. I know sneakers are cheap at WALL MART but sliding a car is instant WALKING.
Title: 7.5 Rear rebuild and gear swap
Post by: bryan163 on July 05, 2012, 12:26:45 AM
Suggestion noted. lol
Title: 7.5 Rear rebuild and gear swap
Post by: TOM Renzo on July 05, 2012, 10:29:40 PM
Just messing around and having some fun. Thanks!!