Another gear advice post

[JohnKcj5]

Hey, guys. Getting ready to regear and need some advice. I'm looking to add some pep and fun.

Current setup: Built AMC 304 (about as much as can be), T-176 , AMC20 rear/Dana 30 front, 2:73 gears, 33" tires.

Driving habits: Never over 60mph. No rock climbing. Offroading is mostly trails and some mud holes. Low locking stock gears does what I need.

Trying to decide between 4:11 and 4:56. I've read a couple of posts that said you don't really use 1st gear on the streets with 4:56. That sounds a little low for my needs. According to the rpm calculator, 4:56 would put me around 2800rpm at 60mph. 4:11@2500rpm

1. What is the idea rpm for cruising an hour or two? At 3000rpm, it just 'sounds' like it's over working a bit.

2. Would first gear be useless in normal driving conditions with 4:56?

Thanks, guys.

 

[Patrick]

A first gear ratio of about 2.7 and r and p of 4.11 will be peppy, but the absence of an OD gear might be the set back. Go ahead and look for that famous fully functional gear ratio chart on line. That is a great resource.

 

[JohnKcj5]

A first gear ratio of about 2.7 and r and p of 4.11 will be peppy, but the absence of an OD gear might be the set back. Go ahead and look for that famous fully functional gear ratio chart on line. That is a great resource.

Yea, I've looked at the chart several times. I'm trying to figure out at what RPM then engine is reving a bit high. Where is the 'comfort' zone for the AMC 304 ?

 

[Patrick]

I looked up your Transmission and, favorably, you have a fairly deep first gear. I would not go deeper than 3.73 gears. That is a good compromise of launch torque and cruising speed without an OD gear. But that’s my opinion. Let’s see what other users have to say.

 

[Lumpy Grits]

3:73
You gonna use locking diffs or LSD?
You really need to go to 1 piece axles in that rear 20.
Hope you have power brakes.
Gary

 

[JohnKcj5]

3:73
You gonna use locking diffs or LSD?
You really need to go to 1 piece axles in that rear 20.
Hope you have power brakes.
Gary

Thanks for the replies.

Going with Eaton Turetrac in the rear and probably an Aussie up front.

1 piece axles are on the list. But one project at a time. I don't ever dump the clutch or bounce it around on the trails anyway. Just want something to take off faster once it's rolling. I'm riding the clutch way to much taking off with these 2:73 gears.

Why power brakes? I'm guessing because the lower gear tends to push through the brakes? I'm in the habit of clutching at the same time I hit the brakes anyway. So it shouldn't matter, right?

 

[Patrick]

John, I gather that you are a light offroader looking to improve your vehicle’s performance in terms of power. If this is the case, you are in the right track with the gearing. You can’t raise your engine’s power by changing gears. But you can transform it for improved torque delivery and fuel economy.

I would advise you to stay away from the Aussie locker. Eaton’s Truetrac front and rear is a superb system but expensive. The cheap but feasible alternative is Dana Spicer’s Trac Loc system, although I am not sure if there is a Dana 30 version or an equivalent for your AMC20 . Power or non assisted brake system is irrelevant.

I have a moderately powered V8. My take off launches were unstable and scary to say the least when I had an open differential. When I upgraded to a Dana 44 with the Trac Loc, my launches were drastically improved. It “insists” on a straight departure. The more aggressive the launch, the more it insists.

I understand that you want the Aussie in the front. It’s overkill and will severely alter steering manners. But in the end, it’s your call. Good luck!

 

[JohnKcj5]

John, I gather that you are a light offroader looking to improve your vehicle’s performance in terms of power. If this is the case, you are in the right track with the gearing. You can’t raise your engine’s power by changing gears. But you can transform it for improved torque delivery and fuel economy.

I would advise you to stay away from the Aussie locker. Eaton’s Truetrac front and rear is a superb system but expensive. The cheap but feasible alternative is Dana Spicer’s Trac Loc system, although I am not sure if there is a Dana 30 version or an equivalent for your AMC20 . Power or non assisted brake system is irrelevant.

I have a moderately powered V8. My take off launches were unstable and scary to say the least when I had an open differential. When I upgraded to a Dana 44 with the Trac Loc, my launches were drastically improved. It “insists” on a straight departure. The more aggressive the launch, the more it insists.

I understand that you want the Aussie in the front. It’s overkill and will severely alter steering manners. But in the end, it’s your call. Good luck!

Thanks, Patrick.

Yea, I'm a light off roader. My first inclination was Truetrac front and back. Then started reading that if one wheel is in the air, the other won't pull. With solid axles, that's not uncommon just crossing a small creek at an angle.
I think I'm gonna go with Truetrac all around and 3:73 gears. Money isn't a problem. I'll get those solid axles too just for peace of mind.

I appreciate everybody's advice.