What next?

[hotrodelrod]

Hey all, Jeep newbie here. I have alot of history with racecars/musclecars/hotrods. I have a pretty well equiped shop. And now I have a 77 CJ7 that I bought as someone elses unfinished project. It has a glass tub/fenders/hood. 3 inches suspension lift, 2 inches body lift, and 2 inches shackle lift. It has 35s. I installed an Ididt tilt column, all new painless harness, fabbed up the shifter linkage, fit a YJ hardtop to it. It has a fresh sbc 350 with 4 bbl and small cam. Transmission is stock(fresh and 3 spd ) as is clutch. Rears are stock as is all running gear. And here in lies my question. What should I do do the rears to handle power and 35s? I will drive it on the road and occasionally do some lite wheeling/trailing. I do have a fresh ford 9 inch 3rd member only (no housing) with 28 splined detroit locker 411s from another project. Please help me with your thoughts!

Thanks,

Hotrodelrod

 

[BusaDave9]

What should I do do the rears to handle power and 35s?

Hotrodelrod

I assume you have a AMC20 rear end.
You must get one piece axle shafts to handle oversized tires.
The 2 piece axle shafts are a big problem with the AMC20

 

[BusaDave9]

An AMC20 axle is easy to identify. The diff cover is very round. Here's one:

If that's what you have you need to get rid of the 2 piece axle. Look at the rear hubs. If you see a big nut like this you have OEM 2 piece axles:

If you see this nut on the rear hub get one piece axles.
A one piece axle will look more like this:

 

[Old Dog]

The amc has 29 spline axles so the 9" with 28 splines wouldn't gain you anything. But with a new carrier and bigger axles it would be a good up-grade.

 

[hotrodelrod]

An AMC20 axle is easy to identify. The diff cover is very round. Here's one:

If that's what you have you need to get rid of the 2 piece axle. Look at the rear hubs. If you see a big nut like this you have OEM 2 piece axles:

If you see this nut on the rear hub get one piece axles.

Thanks Busa. So if I upgrade my axles I should be ok? I know I also need more gear...maybe 456s. I see you are from Durango! Been there twice while hunting San Juan National Forrest. Love it.

 

[BusaDave9]

I have to disagree with OldDog on the 9 inch ford. There's a lot more to an axle than spline count.
IMHO the 9 inch is far superior to the AMC20 .

 

[Old Dog]

I have to disagree with OldDog on the 9 inch ford. There's a lot more to an axle than spline count.
IMHO the 9 inch is far superior to the AMC20 .

I agree the 9" is a better axle housing, I was just comparing the axles themself. And they would be easy to up-grade

 

[BusaDave9]

Thanks Busa. So if I upgrade my axles I should be ok? I know I also need more gear...maybe 456s.

Yes, upgrade to one piece axles. I run 4.88 gears with 35 and later 36 inch tires. 4.56 should be fine too.
The next weakest area on the AMC20 is the axle tubes and where they go into the pumpkin. It's not a big problem but some people add some welds there or better yet truss the axle. If you go to all that trouble you might as well install a Dana 60.

I see you are from Durango! Been there twice while hunting San Juan National Forrest. Love it.

If you can get down here, join us for the http://www.jeep-cj.com/forums/f100/2nd-anual-colorado-jeep-cj-com-trail-ride-12496/

 

[Manhattan]

Do you play poker? Familiar with the term "pot committed"? Give this build a lot of thought. Your screen name implies you like HP and probably never stop looking for more. I don't want to deter your from building a model 20 rear. It's not a terrible axle. Actually, the ring/pinion is damn stout. But as others have pointed out, the shafts need to be replaced and the tubes themselves aren't overly stout.

I've had two CJs on 35s - both with the 20. I did bend one housing - jumping. Unintentionally launched a bit off the top of a very steep, long climb... but that could be filed under "abuse". That Jeep was powered by a built 360 that Edlebrock estimated at 340-350hp. The axle held up fine otherwise for several years.

My current build is similar - model 20, allow 1-piece shafts, Detroits, 4.56 gears, SBC...

But - if I were starting from scratch, I'd start with something else. I'd look for a Dana 44 from an '86 or find a Ford 9", Dana 60... ESPECIALLY if I thought 38"s or bigger HP were in my future... but I'm pot-committed... too much $$$ in the axles to stop now.

 

[hotrodelrod]

Do you play poker? Familiar with the term "pot committed"? Give this build a lot of thought. Your screen name implies you like HP and probably never stop looking for more. I don't want to deter your from building a model 20 rear. It's not a terrible axle. Actually, the ring/pinion is damn stout. But as others have pointed out, the shafts need to be replaced and the tubes themselves aren't overly stout.

I've had two CJs on 35s - both with the 20. I did bend one housing - jumping. Unintentionally launched a bit off the top of a very steep, long climb... but that could be filed under "abuse". That Jeep was powered by a built 360 that Edlebrock estimated at 340-350hp. The axle held up fine otherwise for several years.

My current build is similar - model 20, allow 1-piece shafts, Detroits, 4.56 gears, SBC...

But - if I were starting from scratch, I'd start with something else. I'd look for a Dana 44 from an '86 or find a Ford 9", Dana 60... ESPECIALLY if I thought 38"s or bigger HP were in my future... but I'm pot-committed... too much $$$ in the axles to stop now.

Manhattan,
Do I know you? (lol) seems you know me! My other toys are a 66 Coronet Convertible with a 500inch BB with a bottle in the trunk...just in case. A 54 Chevy truck with a mild but supercharged 355 sb, and a 96 lt4 corvette with a Vortec Supercharger.
All said though, when would you need more than 300-350 hp in a jeep?

 

[Manhattan]

Manhattan,
Do I know you? (lol) seems you know me! My other toys are a 66 Coronet Convertible with a 500inch BB with a bottle in the trunk...just in case. A 54 Chevy truck with a mild but supercharged 355 sb, and a 96 lt4 corvette with a Vortec Supercharger.
All said though, when would you need more than 300-350 hp in a jeep?

I think we all have a common gene

The thing is, horsepower is getting cheaper. 300hp is pretty tame by today's standards. And, while "rock crawling" was once done at a CRAWL... today, it's done on 52s, in tube rigs, cranking over 700hp and it's done more like mudding - WOT and aim for the top. But... the old model 20 hasn't gotten any stronger.

It's funny, I was literally at the builders' shop when you posted - we were standing over the engine talking about the right cam, injector size, heads... He said, "For the short term this will be great.. " I interrupted "You mean for the 'permanent' term - 325hp in a 3,000 lb CJ is plenty"

This Power:Weight ratio is already ridiculous for a 7' tall CJ with more sidewall than an entire drifting event. A 2012 Camaro Z28 would need 30hp more to MATCH my CJ's Power:Weight ratio! Nope. I don't need more HP - there I said it. Quote me later.

 

[3QuarterTon CJ]

The Phord 9" from an early shoe-box Bronco fits in the back of a CJ nicely. I had one in mine for a few years, and I didn't move the spring perches to install it either. They are just a tad bit wider than the Jeep rear but if you have flares it's not an issue.

 

[3QuarterTon CJ]

Oh and you can install rear disc brakes on the 9" with calipers and carriers from a Lincoln Versailles, and the rotors from the front of a Jeep Dana 30 .

 

[hotrodelrod]

The Phord 9" from an early shoe-box Bronco fits in the back of a CJ nicely. I had one in mine for a few years, and I didn't move the spring perches to install it either. They are just a tad bit wider than the Jeep rear but if you have flares it's not an issue.

Ive been talking to a guy with a 78 bronco rear but my reading tells me it is 65". This is not the rear your talking about, right? How wide is the rear you are speaking of? How wide is "doable" on a 77 CJ7 ? Thanks

 

[BusaDave9]

How wide is "doable" on a 77 CJ7 ? Thanks

Go as wide as you want but your narrow track CJ has 53 inch wide axles

Narrow track is 56 inches wide.

 

[CJim7]

This is my kind of thread ... Horsepower and how to handle it

The corp 20 will handle the power, as mentioned already, with the addition of 1-piece shafts. The next problem involves the tubes spinning in the housing (also mentioned) and easily solved with some welding.

The wall thickness on the tubes leaves something to be desired, but is a moot point as far as power is concerned. People bend these axles by launching their rigs...tire size and hp dont play a role.

That said, my 401 puts out a healthy 430 horses combined with compound low gearing through the drivetrain. I run 36" TSL's and have no issues with the rear 20 (which is locked). I beat the hell out of this thing on a regular basis over Volkswagon sized rocks and have dropped the hammer on pavement more then a few times.

I love the Ford big bearing 9" though....and built up a little bit it's as strong as a D60. If I ever win the lotto, my first purchase is going to be a front 9 (lots of $$$). And at that point, I'll ditch the D60 project....the 9" weight/clearance is just all kinds of awesome

 

[hotrodelrod]

This is my kind of thread ... Horsepower and how to handle it

The corp 20 will handle the power, as mentioned already, with the addition of 1-piece shafts. The next problem involves the tubes spinning in the housing (also mentioned) and easily solved with some welding.

The wall thickness on the tubes leaves something to be desired, but is a moot point as far as power is concerned. People bend these axles by launching their rigs...tire size and hp dont play a role.

That said, my 401 puts out a healthy 430 horses combined with compound low gearing through the drivetrain. I run 36" TSL's and have no issues with the rear 20 (which is locked). I beat the hell out of this thing on a regular basis over Volkswagon sized rocks and have dropped the hammer on pavement more then a few times.

I love the Ford big bearing 9" though....and built up a little bit it's as strong as a D60. If I ever win the lotto, my first purchase is going to be a front 9 (lots of $$$). And at that point, I'll ditch the D60 project....the 9" weight/clearance is just all kinds of awesome

I guess i really need to sit down and figure this out! Sounds like the AMC20 will be fine after axles($275)locker($599)gears($225)welding(free!)

I have a fresh 9 in. 3rd member with locker, 410s, but 28 sp. Will need housing($200) shorten housing and axles($?), driveshaft work to mate, etc
Does it make since to dump approx. $1100 and time into the AMC20 ?

 

[Old Dog]

Does it make since to dump approx. $1100 and time into the AMC20 ?

I did BUT if I had a 9" I'd put the money in it.

 

[CJim7]

I did BUT if I had a 9" I'd put the money in it.

I think I agree with this

Not sure I would cut down the axle though.....what are you planning for the front? a Ford 9" is a good option in stock width (not too wide, not too narrow)

 

[hotrodelrod]

I think I agree with this

Not sure I would cut down the axle though.....what are you planning for the front? a Ford 9" is a good option in stock width (not too wide, not too narrow)

The axle width from the 78 Bronco is 65" wms to wms. Thats not too wide? I am confused!