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Ford 8.8 conversion

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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2017 at 6:41am
You have another choice for axles though -- the late model Ranger axle is 1.5" narrower than the Explorer axle. It's not hard to put Explorer disc brakes on the Ranger axle. See www.therangerstation.com, tech articles.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2017 at 11:45am
Is an 8.8 Trac-Lok better than an AMC Twin-Grip?

Are Explorer 8.8 solid rotors better for fade resistance than a heavy-finned replacement drum?

For drums, higher CoF shoes for more braking torque and with a higher temperature range to improve fade resistance are available from Porterfield for about $100 a set. Match well to an equivalent front pad upgrade.

Anyone considered fitting Cherokee/Wrangler front rotors on the rear of an AMC20? Looking at specs, should pilot correctly and correct bolt pattern, so if you trimmed the drum backing plate or made a new axle retaining plate and added a caliper mounting bracket, e.g. a stock-car type GM caliper bracket, wouldn't take much to go to vented rotors on the back.
https://www.summitracing.com/int/parts/ben-prt1602fc/applications/?ibanner=SREPD2&retaillocation=int

Anyone know what an Explorer 8.8 weighs vs. an AMC20?

FWIW, my 74 Javelin AMC20 measured 61" flange-to-flange with the pinion offset 9/16" to the passenger's side. Perches are 43 1/2" on centre. It has the stock twin-grip and 3.15s. Wanting to change gears, so considering options ... not a fan of the C-clip retention on an 8.8.

Thanks,RD.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2017 at 11:58am
I'd say they weigh about the same. Track loc is weak and I have seen plenty with cracked cases. As with additional costs, an after market carrier would be looked into. When I got my F150 rear, it had 3.73 gears with a track loc. The ring gear had a broken tooth and carrier cracked. So, I would suggest opening the cover and checking it out.

My truck rear is 65" flange to flange and will be using Mustang GT wheels. I plan on cutting the the wheel opening lips on all corners, as I do not use trim.

Like I said, after all is said and done, a wee mods to strengthen an AMC20 will do well enough, and cost you about the same if not saving a few coin. Though pre early 72 Twin Grips are not two piece, so check your unit out for tolerances on the clutch pack. The one piece can wear out the case.

The main thing about AMC20, is to key the axle and strengthen the tubes near the center.

You should look around at costs for rebuilding your AMC20 to what you want, including strengthening, and compare the cost to redoing an Explorer rear to what your needs.

I chose to use Explorer 8.8 axles, once slightly modified outer flange diameter. As it was part of some DIY mod online for using 4x4 Explorer 12" front vented rotors on a rear end.

They slide over and are inboard. Just have to weld a bracket on the axle tube to mount a Ford or GM rear caliper.




Edited by 304-dude - Jan/10/2017 at 12:05pm
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ADAM12MATADOR Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2017 at 12:18pm
28 spine Trac-Loc  units are no longer available as they are now obsolete. Those were last used in 2004. The Explorer rears have the center sections offset 2" to the right. To do a correct swap you have to cut 2" from the left side tube and use a right side axle. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2017 at 4:24pm
So far I have $125 for the rear end, $30 in perches and $40 for U bolts = $195. I'm not swapping axles in the 8.8 because I don't really need to. I still need the drive shaft but I had to do it anyway with the o/d trans swap I'm doing now. There's no way I could buy a set of gears, bearings, seals, axles and a limited slip carrier to replace what's in there now. You can't buy a used AMC 20 with a decent gear and L/S for what I have in this - and I already have the disc brakes on mine. Oh and I can also do all the work too. This is one of those YMMV swaps for sure.

"Hemilina" My 1973, 5.7 Hemi swapped Javelin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401harry Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2017 at 4:33pm
The only good bolt in Ford 9 is the Granada/Versailles rear. They can still be had but are not easy to find. You can request the part through a recycler and they can locate one which worked for me in the past. I also found one on CL for 200 bucks with a good 3:50 carrier. Moser sells off the shelf axles for them and they have the big web housing. like you said disk brake upgrade is cheap but the Strange center with detroit locker pushed up the price considerably for me but its the last axle I need for the Spirit
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2017 at 6:17am
Keying the axles on an AMC 20 is very old school and really doesn't help much, if any. For one you'd have to use hardened keys. The factory key is regular key material and is only there to assist in putting the hub back on the way it came off when removal is required (for bearings and/or seals). The strength is in the tight fit between the hub and tapered axle. Torque the nut every 10 years or so to 250 ft/lbs.  -- loosen then torque with the wheel off the ground. Under normal driving you can do this every 20 years or so, that's why AMC never specified an interval. Hard racing requires one piece axles, but people have run the two piece (kept properly torqued) with 500-600 hp, cheater slicks that fit the wheel wells (about 8"), and good hook-up in the lighter cars (Javelin, AMX, American, Hornet, etc.) with no issues. They usually re-torque the axles every couple seasons or so.

The rear brakes do no more than 30% of braking, in some cases less. Solid rotors are usually fine for the rear, and most manufacturers use solid rotors in the rear for cost and weight savings.  Vented certainly won't hurt, just cost and weigh more with little (if any) gain. Cherokee rotors will work as described. You lose the parking brake unless you use GM calipers with the parking brake built in. Remember to use the parking brake occasionally to keep those properly adjusted. You could also install a manual caliper in another location. The little go-cart calipers work fine for parking brakes, but don't expect much out of using it as an emergency brake.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2017 at 8:06am
For the brakes, most cite the rear discs on the Explorer 8.8 as being an upgrade over drums. If the solid rotors don't have more thermal capacity than drums and don't dissipate heat quicker, not sure they are much of an upgrade ... other than not needing as much attention to ensure they are kept in adjustment.

Assume a junk-yard 8.8 should have the same attention to rebuilding as if rebuilding a stock high mileage rear? Main advantages seems to be availability (especially for something needing a narrow axle) ... possibly with gearing to suit an OD trans & with limited slip and eliminates the AMC20 2-piece shaft concerns ... if you are ok with the 8.8 C-clip retention and changing some other bits to fit.

Cost-wise, for me it's likely simpler just to do ring & pinion swap.

Thanks,RD
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2017 at 10:06am
I went through this entire thought process two years ago. The AMC 20 that was in the car had developed a nasty chatter, so rather then deal with how best to rebuild the posi unit, and as long as I was at it, upgrade brakes and axles.
I was certain I was going to do the 8.8 rear axle and get trac-loc and rear disc brakes etc.
Then I was having trouble getting a good core to use, so I looked at the new Dana 44 from Moser.
I did some number crunching, and at the end of the day I just conceded and went with a Moser 9-Inch, just like every car builder does.

It was more money than some other options but it was EASY. I love all things AMC, but having unique custom everything is a bit exhausting. Now at least the rear axle is a common high-perf part I don't need to worry about in any way.

Point is this, before you spend any cash, run the numbers on an aftermarket 9-inch if your are building a rear axle for a high performance application. The cost of a new housing, axles, and brakes is reasonable. The varying cost of center sections is where things can get expensive.

Edited by 343sharpstick - Jan/11/2017 at 10:14am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Floorman Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2017 at 7:58pm
Wow a lot to digest and consider. Thanks for the info. I appreciate everyone's time and input.
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