The reason I ask is because, I'm getting a free gsl shell, and I just so happen to have a 302 and tranny laying around. I know it's sacrilege, but I still have my 12a powered SA. Sorry if this has been covered, I couldn't find anything with the search. Thanks in advance.


-Mike

 

I'm doing the same thing, 5.0 HO out of an 88 Lincoln.

You should be fine, I've read that people are pushing 300 horses through them with no problems whatsoever!

I'll be interested to see your car once it's done. Don't worry about it being "sacrilege"... Even though there are some guys here that will give you a hard time about it, I think there are plenty of CAR GUYS who understand that a car is what it's owner wants it to be.

 

just remember that a lot of the people that push 300 hp to them are turbo guys, turbo isn't the same as NA and especially since its a v8 with quite a bit more torque. not sure if it will work forever. my rear end is starting to go out, and i have a stock 13b. i guess it depends on how you drive, and how good your rear tires are.

 

My suggestion would be buy a set of Moser axles from ReSpeed, those will hold up. Pnly proble is you need an 84-85 rearend for them to fit. As to how much torque the S4 diff can take, no one has answered that yet definitively. Large sticky tires and standing start clutch dumos will eventually take out most any 1st gen diff. If you're going with an auto tranny, that will be much kinder on the diff.

 

"its"

Sorry, wouldn't let me edit the post and it was really bothering me....

Regarding the Turbo cars... that's true, I suppose, the reading I had done was over at V8RX7Club.com, so, like I said, you should be fine...

 

Sacrilege indeed, you should be slowly and painfully dismembered for such a crime. But, I figure it can't hurt to help you out as long as you dont tell anyone, hehehe.

The 84-85 gsl limited slip rear end with moser axles works great for tons of power in rotary motors, cause they generally cant produce much torque in the low end, and do not usually have a very strong rollout. With a big massive V8 spinning at high rpm's and dumping the clutch, the sudden shock would most likely snap the small differential. I would (if I were a traitor) go ahead and shorten a ford 8.8" rear end to the width needed to fit the RX-7, since the engine, tranny, and driveshaft are going to be different. You can use the live axle Mustang rear end, or go find an '89-99 Thunderbird independent rear end and swap the 8.8 differential into the IRS. I believe supersixmotorsports.com?? lists a link somewhere to a set of moser axles for the thunderbird, that should get you an IRS that'll hold plenty of torque. Sorry I can't help you any further about finding the moser axles, it might be easier to contact moser directly. Good luck, have fun, and remember to yield to all rotary traffic! heh heh heh

 

i think i read on grannys that the gsl rear was good for around 500hp from a v8 with stock axles. the rear ends are good for about 2 low 9's 1/4 mile passes b4 you need to change the axles.. i am also referring to the 83.5-86 rear ends with the larger axles..

but i dont know i have not done either im just passing on what i have heard

you should be fine tho

cheers PaTricK

 

Yep, it's on there site but you have to dig around to find it. "the 84-85 big axle rear end is equal to a Chevy 9" rear end"

 

WTF a chevy 9"?


I broke my 85 GSL rear end a year ago with a TBI stock port 12A.......147Hp......8 inch wide drag radials.....6,000 RPM launch. SNAP-CRUNCH: Instant tow truck.

Good luck.....MAKE THAT 302 A 331, and then back it up with a competition engineering 9" Good for 900hp with strange axles. I also recomend the Richmond SUPER T10 road race 4 speed, cuase a 7 with a 4 speed stick would be the shizz....

Have fun though.

 

Do you have the GSL or the GSL-SE rear? There is a huge difference.

Also whoever said that any Mazda rear end is as strong as a Ford 9" needs to have their head examined!!!

 

Soon as my GF's jeep blows up, any day now. I'll trade you the Dana (36 I think) out of it for the GSL rear. I'm just outside of portland.

 

Not really. The -SE rearend has different axles in it, and a different gear ratio, and fewer clutches in the diff, but they're the same unit. I have a GSL-SE rearend with 12A axles in my car right now. (I really miss the 12A diff)

Now, Series 1/2 and Series 3 have a huge difference... the axles and axle bearings are larger in Series 3 and the differentials necessarily have different side gears to take the larger axles. You can't switch axles between the two different bearing sizes.


Strength-wise, you won't be able to get enough tire under the car to hurt the rear, so don't worry about it. Rice Racing regularly put near 600hp through one and he just changed axles every 20,000 km as preventative maintenance. (I suspect Moser axles would eliminate this concern)

I did split a housing but that turned out to have been due to collateral damage from a sideswipe collision - the Watts link bracket made a crack and the crack propagated over time. Solution - don't get sideswiped and run a Panhard or just brace the Watts to not be in single-shear.

 

"Not really. The -SE rearend has different axles in it, and a different gear ratio, and fewer clutches in the diff, but they're the same unit. I have a GSL-SE rearend with 12A axles in my car right now. (I really miss the 12A diff)"


they both have the same amount of clutches, but the gsl is like 2-2 and the se is 3-1

 

everything in the diff can be upgraded for extreme duty except the gear-set itself.

this summer I'll find out if WPC coating can make an appreciable difference.

 

All I have ever seen fail on these rear ends are the axles. The Slick tired roadrace cars put allot of side load on the axles and they snap them at the spinles and flange. I run the small bearing rear end in my race car (lighter) and all I have ever had issues with were the bearings and seals - they last about two seasons

I have looked at doing this swap too. I think the stock rear end is okay for this as long as you are building a street car. The real issue with the stock rear end is gear ratio. At 3.90 the ratio is pretty steep for a V8 - this is especially true when you factor in tire diameter which is about 23" on an RX7 (unless you do a wide body). A stock Mustang from 88 has a 25-25.5" diameter tire and I can tell you from experience that a 3.73 or 4.10 rear end in a street mustang is pretty sporty. First gear in a mustang with that kind of rearend is really short. For this reason, I was looking at doing an 8" Ford rear end instead of the stocker for a v8 swap.

 

I was corrected a while back when I said that the -SE rear is stronger than the GSL rear. The GSL rear end has a thicker ring gear, and thus can handle more power than the -SE rear end.


FWIW I blew a S3 axle on 185/70R13 BGF All Season Radials with a 5500rpm launch. The separation force between the pinion and the ring gear crushed the crush collar that is used to set pinion backlash and torque (the crush collar sits around the pinion shaft), which blew out the front seal. I didn't rebuild the differential because I had to cut it out, and I didn't have the proper tools. Plus it was a drum brake rear end.

Video of blown rear axle:

 

One thing many of us overlook is the age of the parts we're running. As an example, when I was in high school a friend of mind had a 59 Chevy with a 348. This was before they had Bicaynes and Impalas, It was the full size model with the teardrop tail lights. He snapped a rear axle, I offered to fix it, even though I had never done this repair before. Those axles had a casting line that ran the length of the shaft. When new, it was straight. When I pulled the snapped axle out, that casting line was a spiral around the axle, somewhere around 2-1/2 revolutions. At the time, the car was 8-9 years old.

Point being, our parts have already gone through many years of heat and torque cycling, each one different. Part of the answer of how much a rear end or the axles can take is often just the luck of the draw on what we've bought from prior owners.

Within a year, he went through 2 diffs. The first one he was driving down the street in an absolutely normal fashion, the ring gear let loose and tossed a tooth clear through the cast iron housing. Whoever repaired the diff failed to seal it properly and the fluid drained out. He came out from class to go home one afternoon the diff had welded itself together.

 

Actually, the -SE has a thicker gear, since when you change the ratio all you can do is make the pinion larger or smaller, and the ring gear has to change thickness to meet it.

Not that it matters, ring gear thickness has zero to do with anything.

The lower the ratio (like in the 5:1 range) the more likely you are to flex the diff away from the pinion, causing gear mesh problems and failure. Honda S2000 people run into this when they use 4.78s and launch on nitrous with traction. (S2000s use the same diff as an RX-7/Miata) I just take a page from the tricks used to make GM 10-bolts live and run really close backlash and use synthetic lube to keep the operating temps down, so the gears don't bind. And I don't launch a heavy car on nitrous with drag radials...

That... isn't possible. The crush collar sees no load. More likely, someone had the pinion nut off at some point and didn't replace the crush collar. I saw a rearend that was converted from late flange to early flange die in the space of a couple blocks because of this problem. He barely made it back home after we put the rearend in the car, everything just sort of fell apart.

I blew a diff out because of doing a massive one wheel burnout. Any diff will die if you do that.

 

I come from the fix it once you break it school of thought. If you break it - Then look for a solution to fix it.


-billy

 

I don't mean to hijack this thread, but I have a question along the same lines.
I have now broken 3 axles in my Solo Emod car. All happened the same way, get slightly air born over a small bump and upon landing at full throttle, SNAP!!. I currently have a shortened 79-83 disc brake housing with the small splined axles. I was wondering what would I need to do to upgrade to the GSL-SE larger diameter axles and diff? would my current 4.875 ring and pinion work along with my third member? I have tried to search for this information and can not find anything.
Thanks,
Paul
13b powered MG Midget

 

I am currently running the Moser axles from RE-Speed and a set of Racing Beat 4.44 gears in my stock SE rear and it is holding up fine so far. I can't tell you at what power level things will start breaking BUT my TII powered SE is currently at 450 HP to the wheels...

L8R

 

I purchased the vehicle with 90k miles, from the second owner, with zero modifications. The second owner had it for one summer and thought the motor was blown (vacuum line from Anti-Afterburn Valve 2 cooked). I bought it with bearing noise in the rear axle. I know it hadn't ever been apart because I had to use a block of wood and a hammer to break the driveshaft away from the axle flange because they were corroded together.

The crush collar (correct me if I'm wrong) goes around the pinion shaft, correct? There is a separation force between any set of gears (why in a R&P setup you have to have a bushing directly below where the Pinion and the Rack interface). The shock of a 5500rpm launch on bad bearings could cause enough separation force between the ring and pinion to crush the collar.

http://www.epi-eng.com/propeller_red...ear_design.htm

 

Since the housing is shortened, what axles are you running?

If you convert to the big bearing/big spline your ring and pinion could be used but not the third member as a whole.

-billy

 

That doesn't mean much - I have to do that even if the driveshaft was off two months earlier. But regardless...

The axial bearing load under acceleration goes from gear teeth - rear bearing inner race - bearings - rear bearing outer race - case. The front bearing essentially does nothing. The reverse is true under deceleration. A handy way of determining WHICH pinion bearing is screaming. (It's almost always the rear one, being the more heavily loaded one, unless it's a lifted 4x4 with a crazy pinion angle, and then it's the front one because it's starved for lube)

The crush collar is only there to provide something for the pinion nut to tighten against. Otherwise, tightening the pinion nut will crush the bearings together, just the same as if you tried tightening your front spindle nut to 180ft-lb. The sleeve sees no load other than the one imparted by the pinion nut.

 

Technically all you have to do is swap out the side gears in the differential, but since you need an entire big-axle diff to scavenge parts from, you may as well just change the differential.

I've changed over a couple differentials, going from S1 to S3 or going from open to limited-slip. The EASIEST way to do it is to leave the gears in the third member they came in, and just switch the ring gear onto the new differential. Don't mix up the diff bearing races, set the backlash to no more than .006", and set the diff bearing preload to 2.5 "notches" away from zero preload. Works just fine, takes an hour or so.

edit: http://www.ohiorotaries.com/smf/inde...24956#msg24956 Alex documented this as I swapped a diff into one of his Sportage 3rd-members...