Ok after reading the 8.8 issues or non-issues for people, I was wondering what all the advantages are of the 8.8. Yeah it's bigger and has a locker??? But how about if I want to take my "one wheel wonder" and turn it into a posi? With my absolute lack of knowledge of cars (please ask bike questions) I wonder if a posi out of a 7.5 ranger or bronco II will work in my '88 5.0 T-Bird... I think both units are 28 spline. I plan on autocrossing this puppy... and be able to drive it home!:confused:
The guts from those rear ends should work fine in yours.
The main reason most people change to 8.8" is because of thier ability to handle more power. My 7.5" broke behind a stock 302 with 140 horses. If weight is a big concern, though, you might want to stick with the 7.5". Changing to an 8.8 will pack about 80 lbs onto your car.
why not put a TC rear in and be done?
When it comes to cars I'm mechanically reclined. The following thread is a little intimidating: http://www.foxtbirdcougarforums.com/showthread.php?t=3664
Also, mentioned two up, 80lbs in weight??? No thanks. I add enough weight when I sit in it:D
Well, just leave the 7.5 in until you get more power. Then when it goes you will be more modivated on which to keep.
I figured if you were doing Auto-X you wanted a light car. You can easily obtain a numerically higher gearset for the 7.5 and a Traction-Lok (posi) unit for it.
I'm in the process of having my 7.5 posi w/4.10's removed to have put in an 8.8 posi. Not sure what it is worth, but it was original to my car when it had a V-6, before I had it changed to posi w/4.10 about 25-30,000 miles ago. I interested in just the rear without the gear, that's cool too. Car is in Owensboro, KY right now.
That's one of those myths that is never going to die... Yea the 8.8 is heavier, but 80lbs??? NO WAY...
Maybe you could weigh the rears so we'd know the weights??? Say with just the axles installed, no brakes..
There was a thread about the weight difference a while back. I'm doing a search but nothing is coming up. I DO remember that it was marginal at best. Like, 10 lbs or something.
That myth will die when I swap my TC rear in, I'm gonna have both rears side by side and weigh 'em both on bathroom scales. I can't see 80 pounds either - maybe if the 7.5 were aluminum you'd see a difference like that, but not iron - hell, the only parts on the rears that are really different are the center sections (the tubes, axle shafts, etc should be pretty much identical)
Woo-hoo I found it.
http://corner-carvers.com/forums/showthread.php?t=187&highlight=8.8+7.5+difference
Sticky this B!
Nice job thunder. You guys had me wonderin' too. ;)
Nice find. I deem it stickyworthy :D
Yes, too bad one can't find it via the search. :(
http://www.foxtbirdcougarforums.com/showpost.php?p=6727&postcount=18
If you wanted True Posi just weld up the spider gears in your 7.5... that way you don't have to take a chance on getting the backlash perfect because you can weld it up with the axle still in one piece. I could never put in a carrier assembly without it later ripping to shreads. I tried carbon paper and lip stick to make sure the tolerances were correct but no matter what the 5 times i changed the gears they all went to !
so WTH actually goes in the 7.5? alot of them sound like bad setup, or maybe defective gears...or is the carrier walking?
That's a fine solution for a drag-only car, though if you ever plan on deviating from a straight line you might wanna second think it. It's called a differential for a reason - it's designed to allow the two wheels to travel at different speeds while turning. Welding up the spider gears creates a "spool", eliminating differential action and making cornering dangerous.
BTW, if you REALLY want
"True Posi" your only option is to install a GM rear end. "Posi Trac" is simply GM's brand name for the same setup Ford has (Ford calls it "Traction lock"), and the actual method of "Limited slip" (which is what all Posi and Trac-lock rears are) can vary even within the manufacturer - anything from the simple clutches like our rears have, to cones (Chrysler), to a mechanical ratcheting locker (GM Trucks), to an electronic locker (Toyota TRD package) and many others.
I've lifted both a 7.5 and an 8.8 and I can say that 80lb figure does seem a little high. I only repeated it because I've heard it from 2 or 3 reliable sources.
What kind of value would you guys put on the 8.8, if you had one to sell, or were looking to buy one, like from an 87' or 88' TC?
Maybe this fits here, maybe it doesn't, but I had 3.73's installed in my 7.5 and found it to provide plenty of off-the-line go. I never abuse the car or mash the throttle, so hopefully I never have to worry about the rear failing.
Chris
In my experience, (I have GRENADED 4, 7.5" rears. one behind a 4.2L V8, and the others behind stock 5.0L's) It is the spider gears and the main carrier caps that let go. The last one I wrecked, I never did find all the pieces of the spider gears, and the caps both broke into 3 seperate pieces EACH. spend your money wisely. go 8.8" or waste your money and blow up a 7.5
And the weight isn't that much more, maybe 20lbs.
A properly built 7.5" rear will withstand quite a bit of abuse. The key is to get a rear end girdle cover (yes, they exist for 7.5" rears) and a good locking center section. After that, thrash away.
So the weight thing...let me explain. I pulled the 80 lb. difference info from two different sources: my mechanic, and a magazine article. The mag--meh, not so sure about them as they've had errors in the past, but still, it felt correct to me. My mechanic--very trustworthy as he's the driveline specialist at the Ford dealership where he works. I think since he works on FWD and RWD vehicles, Focuses to F-350's, and also races Mustangs on the weekends, he can give a very good idea of weight differences between components.
A standard Cougar/T-Bird 7.5" open rear end with 2.73 gears and 9" drum brakes is the baseline. The top-of-the-line, I suppose, would be a 1987-88 Turbo Coupe 8.8" locking rear end with 3.73 gears, 10" discs and quad shock brackets. Fully loaded with brakes and gear oil, the difference in weight between those two rear ends is quite dramatic. Is it exactly 80 lbs.? Never said that. Is it realistically more like 40-50 lbs.? Possibly. I do know that I can carry a basic, loaded 7.5" rear around by myself but need help with a loaded 8.8" rear. And I'm not that big of a pu$$y...I can lift some fairly serious weight around. So it the real difference between 7.5" and 8.8" rear ends a mere 10 lbs.? I don't think so. Bare, possibly. Not fully loaded. No way. I think it's funny how everyone jumps to conclusions about "only a 10 lb. difference" when there aren't even any brakes attached. Isn't that how you, um, you know...USE a rear end in the real world?!
In the near future I will have the opportunity to weigh both, fully loaded to fully loaded, and will report actual numbers when I get them. I also have separate components (gears, center sections, 9" and 10" drums, etc.) that I'll throw into the mix, just for solid numbers. That should help smooth things out.
I know of several 7.5 that have been used and abused that are still in working order.
buddy of mine had a Dominator Mustang that had a 7.5 under it-withstood a bunch of high-13 second 1/4 runs...
I pulled my TC's 8.8 just last week, and I will say that there IS more than 10 pounds of weight difference between it and a 7.5, and this was the complete rear, even the quad shocks :D
I could barely lift it into the back of my truck, and I ain't no wimp! :giggle:
I can pack around a 7.5 by myself, but I sure as hell can't an 8.8..
The mustang 8.8" dont seem to be that much heavier the the 7.5"ers I will be pulling the differential out of my '88 stang this week and I will weigh it when I do so we have numbers on those as well.
I believe that the 8.8 axle tubes are only marginally larger as well. I changed the 7.5 trac-loc in my 86' for a 90' Lincoln 8.8 trac-loc w/rear discs and didn't notice much of a weight difference with the exception that I had left in the stock gears. BIG mistake!! I have since pulled the 8.8 and swapped in a 03' Cobra IRS. Now that does weigh 80# more than even the 8.8 live axle. But the trade off is worth it for me as I too will be autocross/road racing my car
The axle tubes on the 7.5 are 2.75" and on the 8.8 they are 3.00"
so rangers come with a 7.5? would a tc rear bolt in the ranger, cause if so ill have a posi unit to go with the 2.3t swap once i find a decent ranger.
Some Rangers came with 7.5's some came with 8.8's. TC rears will not bolt into a Ranger - the Ranger has leaf springs (and brackets necessary to install them), while the TC rear is setup for four link/coil spring (again, with brackets to install 'em)
, ill find a way to make it work, thats one thing im good at, making things into stuff its not ment to be, like a roll cage into a go cart intake and exhaust lol
Just swap the differential....
wow i totally didn't think of that
Ok... so let me tell you guys from my experience with 7.5 rear ends.... You know my car... it's making around 500 RWHP and 400+ ft. lbs of tq. in an auto... I did shatter one rear beyond coming back and bent both stock axles.... well twisted...lol
So instead of replacing it with a 8.8 I had it built the right way and now it has been amazing even running 11's with slicks...
They key is to have it built right and by someone who is going to take their time to do it right for you...
I have FMS 4.10 gears
A Detroit TruTrac unit
Yukon Chromoly racing axles
and all new racing carrier bearings and shims...
A lot of people under estimate the capabilities of these rears, DON"T
I like the 7.5 and maybe one day upgrade...till then... I'll rip up the track with what I built FORD tough...lol
7.5" rears are like T5 trannies. Some will take years of abuse behind a maniac with a lot of power, and some will snap in twain while riding around town.
Hey guys, just reading the June '07 Car Craft, and they have an article about 8.8" rears. I noticed they mention that starting in '94 mustangs they had 31 spline axles and carrier. I thought the 31 spline axles were in trucks only? Hmm, could Car Craft have made a boo-boo?
I looked for a long time to find an 8.8 for my 84 cougar! After looking for so long i took my 7.5 rearend in and had it built with a locker! and 4.11 gears! It takes all the power i can give so far! Witch is a 351 windser with 150 shot NOS! if i go to about 600hrs i will look for another rearend!
You are on borrowed time.
8.8's are everywhere if look around.I see them on Ebay everyday.We just pulled a TL 8.8 with 3.73 gears fron a '96 Explorer (disc brakes),welded new spring perches on and installed it in my friend's '67 Mustang coupe.Perfect fit.I know,that's not a Thunderbird or Cougar,but,the Turbo Coupe and Mustang rears are out there for the picking.
Almost all locking units for the 7.5 eliminate the spider gears. Couple that with a rear girdle and you have a rear that is much stronger than a stock 8.8.
Would a built 8.8 be stronger than a 7.5? Sure! Don't knock a 7.5 done correctly though. It's what I have......Of course, I don't put nitrous through mine either.
i had the stock 7.5 in the ranger with the stock 3.45's in it (still open). i never had any issues with it, and i was making a good bit of power at the time (right around 280 to the wheels). i've since swapped it out for the new build, but i never had a single problem with it and i beat the hell out of it for about 4 years.
the 7.5 is stronger then a lot of people think.
Untill your coochng around 350t then leave the 7.8. WHen u get the mad power 350t get a 8.8. Just to let you know a 4.10 gear is a drag gear so go with around a 3.27 gear or 2.81 which has a higher speed but lower acceleration but your AutoX how offten are u taken off form a dead stop.
I assume by 350t you mean 350 ft-lbs of torque?
If done correctly a 7.5" can handle more than that.....
I'm told mine will take over 500 in it's current form. The locking unit is rated for 800....
Then again I see you were talking about the 7.8.....:hick:
As said before a similarly built up 8.8 will be stronger than a 7.5 barring some part defect.
I couldn't brake my 7.5,I tried.Of course its for sale!
If you build it right it will not come apart.
I had a 7.5 with 3.45 gears from a Turbo Coupe.That thing took all the abuse I gave it,and never gave me a minute of trouble.
What about picking up a 7.5 out of a sn95 v6 stang, should swap right in, correct?
Rear disc and all??
Look..... you can make a 7.5 do crazy things if you build it right..... Take mine.... it's a 7.5 with a detroit Tru-Trac locker, Ford Racing 4.10 gears, Moser C-Clip Eliminators, Yukon Axles, T/A performance rear end cover with main supports and fully welded Axle tubes..... I am pushing over 500 RWHP and close to 500 ft. Tq. to the wheels with 295/45/17 M/T drag radials. CHE upper control arms and maximum motorsports lower control anti hop bars. I'm running low 11's with no problems.....
Now I have snapped axles and c-clips but that was when the rear was in stock form. I have been told that this rear setup the way it is that I can handle 700HP with no problem..... The only problem is will the floor boards.... I have to next weld on battle boxes to prevent the torque from ripping the floor apart....
any question on these rears, please feel free to ask....
I'm hearing REAL good things about Yukon products. The whine fro the Richmonds I threw in ('cause NOBODY had a set of FRPP 3.45's) @ 40 MPH is ever so slight, but it's enough that I want to swap them out....and yes they were installed correctly. The whine has been constant. Hasn't changed a bit.