4" lift recommendations/warnings

[oldyeller]

Hey guys, this is my first post, and first jeep. I have a 1980 CJ7 Renegade AMC 304 automatic. This jeep only has 57,000 miles on it, bought and owned solely by a friends mother. So you can imagine how good of a find this is. It has been in storage for 4 years and I'm "resurrecting " it now. It seems to finally be road worthy and reliable so now it's time to start with the fun stuff.
I want to know what 4" lift kits you would recommend for someone who will not be rock crawling or jumping the Grand Canyon. I want to get clearance for 33 or 35" tires and maintain or improve the ride. The only problem I currently have is the castor angle shims 6 degree I have installed still hasn't cured the unstable steering. I don't trust anyone to drive the jeep because it will drift across the road constantly. Hoping the new bushings and shims that come with most kits will help this. "Should I install a special steering dampener?" I have looked at rubicon express, rough country, sky jacker. And so on. Not really scared of the price if it will perform. I'm rambling, but I have learned a lot. I know I have been bitten by the jeep bug. I really enjoy this thing. Oh yeah, already checked steering box, steering components, rod ends ball joints,etc steering shaft, bushings may be worn some but 57,000 miles wouldn't wear them out I wouldn't think. 37 years might. I y'all would recommend which kits to buy and to stay away from I will get one here and get started. Thanks!

 

[Belizean]

Welcome to the forum. Nice looking jeep. Can't help you with the lift because i only went with a 2 1/2 inch lift. Someone will though. Good luck !

 

[Lumpy Grits]

:ww:

35" tires on the stock driveline will kill it PDQ.
Drifting indicates the toe-in is out of spec also.
What R&P ratio are you run'n?
I run 33's and did a 2.5" suspension lift and a 1" body lift.
LG

 

[diddy2003]

I went with a 4 inch YJ skyjacker lift with bilsteins. I also am running a borgeson power steering shaft, MORE power steering HD mount and brace, H1 power steering pump, Navajo power brakes, JKS disconnects and 4.10 gears. The AMC20 is also welded and has one piece shafts. What gears do you have? My Jeep could barely go up a moderate hill with 33s and 2.73s. 4.10s and 35s, with a T-176 , seem to be a great pairing, although I wish I had Overdrive . I'm right around 3000rpm at 50mph. I'd rather the stronger Transmission over a T-5 though, which would grenade with a V8 and 35s.

 

[PistolDave]

Why have you installed 6 degree shims in the front axle? If the original suspension has not been modified those should not be necessary. Have you measured your caster angle? Should be around 4 degrees or so from the factory. Might want to double check and see if the shims were installed in the proper direction, you might have -2 degrees of caster angle now. The reason I ask is because I had a buddy do this very same thing to a YJ that he was working on. The upper part of the knuckle should be inclined back toward the driver. Looking at it from the side, the knuckle should be raked like the forks on a motorcycle. If they ARE installed in the proper orientation, you may have 10 degrees of caster angle. Not sure what kind of issues that might cause. If you already knew all of this, please disregard.

Dave

 

[PistolDave]

I'm right around 3000rpm at 50mph. I'd rather the stronger Transmission over a T-5 though, which would grenade with a V8 and 35s.

Not trying to derail the thread, but you might want to check your tach, my gearing calculator shows 35's and 4.10's to be turning 1968 rpm at 50 mph in 4th (1:1) gear. My tach indicates 2900rpm with 4.56's and MTR-
K 35x12.50's at 65 mph on the gps.

 

[diddy2003]

Not trying to derail the thread, but you might want to check your tach, my gearing calculator shows 35's and 4.10's to be turning 1968 rpm at 50 mph in 4th (1:1) gear. My tach indicates 2900rpm with 4.56's and MTR-
K 35x12.50's at 65 mph on the gps.

Ok, I will. Thanks.

Gear Ratio Calculator

I will drive around with a GPS speedo app and take a look at the tach. It was definitely higher than what it says on that site. Thanks.







Stock tach and speedo. RPM butt dyno feels accurate? Maybe I have 4.88s . . . .

 

[Lumpy Grits]

The appropriate R&P ratio takes a lot of the torque load off the tranny and t'case. That means a longer life.
FWIW: My T-5 and 4:1 t'case have worked well for many, many years. That said, I do have a spare T-5 sit'n on the self, just in case........
LG

 

[Lumpy Grits]

Ok, I will. Thanks.

Gear Ratio Calculator

I will drive around with a GPS speedo app and take a look at the tach. It was definitely higher than what it says on that site. Thanks.







Stock tach and speedo. RPM butt dyno feels accurate? Maybe I have 4.88s . . . .

I would suggest you pull the rear diff cover and count the ring gear and pinion teeth.
What diameter are your tires??
Don't rust the OEM tach to be all that 'rite' either. Mine reads 200-300rpm high above 2K, rpm.
LG

 

[diddy2003]

I would suggest you pull the rear diff cover and count the ring gear and pinion teeth.
What diameter are your tires??
Don't rust the OEM tach to be all that 'rite' either. Mine reads 200-300rpm high above 2K, rpm.
LG

They are 35s. I might have some tach error. I'm going to have my buddy check it out.

 

[oldyeller]

Thanks to everyone who responded. I am not sure of the gear ratio, I just had the inspection cover off to check the condition of the teeth and didn't think to count them. As far as power loss I hope the V8 will make up the difference in tire size. I also recall a concern about toasting the Transmission and that is a real concern, but like I said I'm not gonna be pushing the jeep too much. The castor shims were installed as a possible fix to the drift in the driving. I have the fat end facing the front with the taper towards the rear which should pitch the differential top forwards, which should in theory help the jeep to track better. It may be doing all it can that's why I am at the lift kit stage of the restoration. I'm hoping if I get a quality kit it will have all the components and fasteners, shocks, and bushings needed. I do not have a factory tach, but it is on my list of things to come, I'm just trying to get it safe to drive by someone other than myself.

 

[Lumpy Grits]

You're see'n 3K rpm on 35's at about 60 mph.
You could well be run'n 4:88.
I sure hope that isn't a stock '20' rear then........
LG

 

[diddy2003]

You're see'n 3K rpm on 35's at about 60 mph.
You could well be run'n 4:88.
I sure hope that isn't a stock '20' rear then........
LG

My buddy has a timing light and we just checked it out. 3000 rpm on the tach is actually 2250 rpm, which puts me right where I should be with 4.10s. So I will have to fix my tach issue. Also, I will be coming up with a better temp gauge. The stock one sucks. I need actual numbers. The 20 isn't stock. Welded w/ one piece shafts. Thanks.

 

[diddy2003]

For checking gear ratios you can do something like this:
https://youtu.be/uU6WJXjZf4Y
I was going to do that next if my tach was accurate.


Or look for the axle stamping, if the gearing is stock.


Jeep Axle: AMC 20

 

[PistolDave]

I have the fat end facing the front with the taper towards the rear which should pitch the differential top forwards, which should in theory help the jeep to track better. It may be doing all it can that's why I am at the lift kit stage of the restoration. I'm hoping if I get a quality kit it will have all the components and fasteners, shocks, and bushings needed.

Sounds like they are installed correctly. If you have access to an angle finder of some sort, you might want to measure your caster, should be in the 4-6 degree range. Measure the distance from the center of the locking hub to the ground. Remove one of the front wheels and support the axle with a jack stand at the same hub height that you measured. Place the angle finder on the flat surface of the lower ball joint. As mentioned by Lumpy earlier check toe-in also. Too much toe in is not good, toe-out is really not good. There is a pretty narrow range that is acceptable. Might need an alignment shop to do this for you.

Dave

 

[Lumpy Grits]

Just an FYI-IIRC you can't go 'deeper' than 4:88 in that 20.
I would confirm the RPM one more time with a different tool.
750 rpm error is a good bit.
Still think it would be best to count the gear teeth, and remove all SWAG'n.
LG

 

[diddy2003]

Just an FYI-IIRC you can't go 'deeper' than 4:88 in that 20.
I would confirm the RPM one more time with a different tool.
750 rpm error is a good bit.
Still think it would be best to count the gear teeth, and remove all SWAG'n.
LG

I did the spinning drive shaft/wheel trick a while ago when I first bought the axle set on CL. I've never counted the teeth . . . . but I'm pretty sure I had my buddy check it out when I had the fluid/seals done. The thing that changed was that I put a 360 in where my AMC 258 i6 / 4.2l was. I didn't realize that the V8 would effect the tachometer. I stopped by my buddy's jeep place today and they stated that's why it was off so much. They are going to find a V8 tachometer and set it up for me.

 

[Lumpy Grits]

The tach 'reads' the firing impulses on the POS(+) side of the coil.
Good outfit to deal with.
Retro Style Performance Gauges and Sets.

LG

 

[diddy2003]

The tach 'reads' the firing impulses on the POS(+) side of the coil.
Good outfit to deal with.
Retro Style Performance Gauges and Sets.

LG

Thanks. My buddy at the shop is going to just find a V8 tach at the shop and give it to me. If he can't get one, I will look at those. I was going to get a good temp gauge, but I would have to find a place to put it. The stock gauge sucks because it doesn't show actual temp. I hit it with an IR heat laser before and it wasn't running hot, but the gauge was nearly pegged this past weekend and I had no idea what that actually meant. I'm going to get one of these, drive it around, get it hot, and see what I'm actually dealing with. Then I can adjust the fan accordingly.

https://www.amazon.com/dp/B002OD0NCG/ref=cm_sw_r_sms_c_api_MrqWzbAG3W9KV

Sorry for the thread jack.

I would really check your gear first before you do anything regarding tire size. It makes a HUGE difference. My Jeep came with a open rear and 2.73. It was terrible, even with the stock 29 inch tires. 31s made it even worse. I lucked out and found a wide track 30,20 set from a 1986 CJ7 with 4.10s and LSDs front and rear. I think I paid 500 bucks on CL. I just found another set a month ago with 4.10s, LSD in the front and a ratchet locker in the rear for 700. A friend ended up buying it because of the deal versus building a similar set-up. You may luck out in the same way. The AMC 304 isn't a powerful engine stock. Bad gears and 35s isn't going to be much fun. I've been searching around for what it may have for gearing and it may have 3.54s? Playing around on the gear calculator, if it has 3.54s, that wouldn't be too bad on the street with 35s? Just guessing though.

How mine sits with the 4 inch YJ lift and 35s:

 

[bh10]

Hey guys, this is my first post, and first jeep. I have a 1980 CJ7 Renegade AMC 304 automatic. This jeep only has 57,000 miles on it, bought and owned solely by a friends mother. So you can imagine how good of a find this is. It has been in storage for 4 years and I'm "resurrecting " it now. It seems to finally be road worthy and reliable so now it's time to start with the fun stuff.
I want to know what 4" lift kits you would recommend for someone who will not be rock crawling or jumping the Grand Canyon. I want to get clearance for 33 or 35" tires and maintain or improve the ride. The only problem I currently have is the castor angle shims 6 degree I have installed still hasn't cured the unstable steering. I don't trust anyone to drive the jeep because it will drift across the road constantly. Hoping the new bushings and shims that come with most kits will help this. "Should I install a special steering dampener?" I have looked at rubicon express, rough country, sky jacker. And so on. Not really scared of the price if it will perform. I'm rambling, but I have learned a lot. I know I have been bitten by the jeep bug. I really enjoy this thing. Oh yeah, already checked steering box, steering components, rod ends ball joints,etc steering shaft, bushings may be worn some but 57,000 miles wouldn't wear them out I wouldn't think. 37 years might. I y'all would recommend which kits to buy and to stay away from I will get one here and get started. Thanks!

The best is a YJ spring conversion with OME Springs. 2nd tier would be BDS or Rubicon Express.

As for your steering first thing is get it aligned get the numbers and go from there.

But yes, check the gears. Id bet you have 3.54's. Might have missed it what tranny do you have?