AMC Eagle Den Forum

The Shop => Axle / Differential => Topic started by: carnuck on September 22, 2011, 11:52:09 PM

Title: Is it true no Eagles were factory twingrip or other posi?
Post by: carnuck on September 22, 2011, 11:52:09 PM
Had someone on another forum state this as a certainty. I've never seen one myself. Anyone see a FACTORY installed one?
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: captspillane on September 23, 2011, 01:22:14 PM
It is a fact that AMC did not offer twin grip as an option for AMC Eagles. The factory considered the front axle more traction than you could need.

The twin grip is also very rare on Spirits and Concords, although the option from the factory did exist.

I am putting a factory posi from a 2wd commanche into my Eagle when I upgrade the axle to a Dana44. It will have a drastic improvement in traction and will not affect the vehicle's handling. A "soft locker" is much more aggressive than the limited slip posi, those will have a noticeable jerk to the rear as you make tight corners. For an Eagle set up for rock crawling it would make sense to put a soft locker in the front axle, but a disconnect must be retained for street driving. A soft locker in the front will make a huge impact on steering and road driving.

The viscous coupling on the Eagle transfer case wears out and is supposed to be routinely replaced. None of us do that. Once it wears out your transfer case is an open differential. If you put the NP231 from a Cherokee in, you'd have low range and transfer case outputs rigidly connected. Thats the definition of the term "Command-trac." There are also alot of Cherokees with "Select-trac," which has an open differential or viscous coupling in the transfer case. The impact of lockers in the front and rear will be more noticeable with a solid transfer case.

All Jeep transfer cases, regardless if they have a viscous coupling or not, have directly connected outputs while in low range.

-Dave Spillane-
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: Hawk258 on October 22, 2011, 01:09:56 AM
Now there is an interesting idea, The newer jeeps have an e-locker for both front and rear. That could be fun for some of the SAS that people have done.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: captspillane on October 22, 2011, 01:46:29 AM
My 2006 Rubicon has the E lockers. They are awesome. The rear is designed to be a very smooth limited slip when its not locked. They also make an aftermarket version that is readily available for the Cherokee Dana 44s going into my Eagles. Those are also limited slip when not locked I believe. At some point I will also try to shoe-horn a cable, pneumatic, or electric locker into the Eagle front axle casting. It may be possible with some machine work.

I will never ruin the Eagle driving experience by putting a solid front axle under any Eagle I own, so its worth working with the original front axle. I also cherish the low center of gravity, so the only lift I will consider comes from larger tires installed with fender modifications only.

In the future I want to make my own front axle that has a better differential with E locker and still connects to the factory half shafts. It has been suggested on this site that a Ford Ranger front axle has the same spline count and diameter as an Eagle front axle. We could have our front axle shafts installed on it if custom axle tubes were made. Obviously any other front differential would not have the bolt bosses in the casting, but anyone who can shorten and modify a differential to the proper width can also make an adaptor to hang the differential from.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: JayRamb on October 22, 2011, 04:16:40 AM
All I know is that both of my Eagles act as if they have Posi/Twin Grip if I want to spin out the back tires, both back tires spin out equally.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: captspillane on October 22, 2011, 04:52:46 AM
I have thrown rooster tails from all four tires on my Eagle many times. Thats with an open differential in the transfer case and two open differentials in the front and rear. The differentials naturally split the torque even without limited slip. The only time I can really tell a difference is when one wheel is totally up in the air. If you put a jack under one tire on your Eagle so that its not touching the ground, it will spin away while the other sits still. If both tires are held up off the ground, they will happily spin together. Honestly limited slip is overrated, since an Eagle that is stuck in mud would be more likely to get out with a low range than a limited slip. Low range lets you put slow steady pressure on the wheels without reving the engine up. Thats usually enough to get all the wheels to play together.

Its true that the factory never put a limited slip in an Eagle. Its also true that my 2006 Rubicon with its wide 33x12.5 tires cannot keep up with my Eagle even with all four wheels fully locked. It got stuck with all four wheels spinning in 8 inches of snow. My Eagle with all open differentials did not get stuck in the same storm because of the skinny tires. It helps that the independent front suspension and low center of gravity lets me go three or four times faster than the Jeep can. In some ways AMC knew what they were doing when they concluded that Eagles didn't need them. Of course we still want them regardless.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: 68AMXGOPAC on October 22, 2011, 08:36:39 AM
I am curious if the inards and axles from a limited slip would fit inside the same year houseing of a non limited slip.
I have a non from a 68 amx, and the guts to a limited from a 68 amx...... any thoughts?
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: captspillane on October 22, 2011, 12:50:11 PM
There may be exceptions, but I do not know of any axle that has a different casing for its limited slip. The limited slip components are all contained in the carrier assembly, which can be removed independently of the axle shafts and case casting. The carrier is easy to remove to facilitate changing out the gear ratio ring. You should have no problem.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: wagonmaster on October 22, 2011, 05:41:32 PM
ive bean dreaming about this very thing for months. my thought was to swap in a ford 8.8 from an explorer with limited slip and disc brakes or upgrade a non lsd with an air locker. of course i would need matching ratios in the front and i havent done all my research on that yet.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: Sunny on October 23, 2011, 10:07:21 AM
Quote from: Regalwizard on October 22, 2011, 04:50:14 PM
I knew I'd read something official somewhere! ;D Page 2F-44 of my '83 TSM:

"A Twin-Grip limited-slip differential is available as an option in all AMC automobiles except Eagle models."

I'm surprised they didn't offer it.
A limited slip differential seems like it would be a great addition to an Eagle. It's one of the first options I ordered on my truck when I got it.

I know my grandfathers Javelin had a limited slip, but I'm not sure if it was factory or not.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: 68AMXGOPAC on October 23, 2011, 12:49:02 PM
I would think it was factory , it was offered in many models as an option with the v8's.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: Sunny on October 23, 2011, 01:15:53 PM
Quote from: 68AMXGOPAC on October 23, 2011, 12:49:02 PM
I would think it was factory , it was offered in many models as an option with the v8's.
'

I was younger when he had it, so it's one of those things I never asked. I wish the car was still around, as it would have gone to me and I could have restored it.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: mick on October 23, 2011, 11:51:44 PM
Quote from: captspillane on October 22, 2011, 01:46:29 AM
I will never ruin the Eagle driving experience by putting a solid front axle under any Eagle I own, so its worth working with the original front axle.

I used to say the same thing. 
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: BenM on October 24, 2011, 11:37:25 AM
I've never run any kind of limited slip, but I've considered the Torsen-type front units in the past. The thinking being that it would reduce overstear in slippery conditions like snow.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: Sunny on October 24, 2011, 12:54:47 PM
Quote from: BenM on October 24, 2011, 11:37:25 AM
I've never run any kind of limited slip, but I've considered the Torsen-type front units in the past. The thinking being that it would reduce overstear in slippery conditions like snow.

There is a pretty noticeable difference between an open and limited slip differential in the snow.
The only thing is, if you don't know how to drive, you'll just end up sliding sideways. Lockers are significantly worse for that.

Anything is an upgrade over an open differential though.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: maximus7001 on December 10, 2011, 05:17:24 AM
So has anyone here put a twin grip into the rear of an Eagle? The trans place I deal with gave me a price of $500 tax in for the upgrade, thats $360 for parts plus 1hr labour plus 12% tax.

I am considering this upgrade and heres why:

My sister and I each bought a 1997 GMC Safari AWD at the same time(still have mine). Both vans had Blizzak tires but mine has a G-80 LSD in the rear and hers an open diff. Drove hers a few times in heavy snowfall and got stuck 2 times, never been stuck with mine in 14 years. With mine I once towed a broken Zamboni off an ice rink and it was like dry cement.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: rollguy on December 10, 2011, 10:33:53 PM
Quote from: maximus7001 on December 10, 2011, 05:17:24 AM

My sister and I each bought a 1997 GMC Safari AWD at the same time(still have mine). Both vans had Blizzak tires but mine has a G-80 LSD in the rear and hers an open diff. Drove hers a few times in heavy snowfall and got stuck 2 times, never been stuck with mine in 14 years. With mine I once towed a broken Zamboni off an ice rink and it was like dry cement.
WOW!  that is impressive!  Not every day someone gets the chance to pull a broken Zamboni! (And now for today's history lesson, Frank Zamboni was the originator of the ice resurfacing machine in 1949, first one made from a JEEP).  I have owned 2 Astro vans and I liked them a lot.  I have only seen 2 AWD Astro/Safari vans (not much need here in CA), and wondered how they would do in inclement weather.  
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: AMCKen on December 19, 2011, 10:44:36 AM
I have a 3.55:1 twin grip out of a 4cylinder SX4.  Proper code stamped an all.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: IRON HORSE on December 21, 2011, 04:50:57 PM
Hi :hello:

    Use of a locker or limited slip might prevent those axles from breaking ?????? maybe.
     
                                                                            Iron Horse ;D
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: captspillane on December 24, 2011, 09:52:56 AM
A locker or limited slip will always increase the torque on the axles. If the axles are locked together, all of the engine torque must be transfered directly to the axles. With an open differential, there is a torque split and there is often less than the total engine torque actually being transfered to the wheels.

Alot of Jeep owners abuse their stock axles for years without problems and then immediately break them as soon as a locker is added. Many odd driving situations that would not normally break an axle will be able to once the locker is added. That's especially true of someone who is accustomed to approach slippery conditions by stomping on the gas. Especially with the stock axle, you will need to be much more cautious and gentle when you accelerate after the locker is added. That's both to prevent breaking an axle as well as to prevent it from locking up and giving your car a slap in the butt around curves.

The good thing is that the axle shafts themselves don't normally break from torque, they break because of flex. A locker just increases the amount of torque the axle sees, and most shafts won't mind. The rigidity of the axle housing is important. The reason my family has had three Eagle axles break is because my brother and I were fond of jumping and tilting our Eagles on two wheels, which the thinner axle tubes could not handle. The center casting is actually identical to the Cherokee rear axle, but its called an AMC 15 because the tubes are thinner.
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: idahoeagle on September 30, 2012, 11:47:02 PM
I haven't seen an Eagle with a limited slip diff before, at least not factory... I have had a few fullsize Wagoneers over the years with them though. Some with 219s and one with a 229. I lived in middle of nowhere Wyoming when I had the last one with the 219 and limited slip rear. It was phenominal in the snow. Definitely would be a crazy benefit in snow country in an Eagle...
Title: Re: Is it true no Eagles were factory twingrip or other posi?
Post by: idahoeagle on October 06, 2012, 12:29:01 PM
You'd have to regear it, but there is an AMC 20 that is the correct width and bolt pattern to use in an Eagle... It was used in 86 only Metric Tonne Comanches. They had 4.10 gears. A very small number had a Trac-Loc limited slip. And an even rarer version actually came from the factory with a Detroit Locker... That was some kind of government special package... You could take a Trac-Loc from a fullsize Wagoneer/Grand Wagoneer from 1980-86 and gear it with 3.54/3.55s and have a great bullet proof rear...