Let's talk crawl ratios!

[Gravy]

I'm running a nv3550, but I have an aw4 (from my old red cherokee) that I've been planning on swapping in. Trans gears in the aw4 are 2.80, 1.53, 1.00, .75

I'm running the box 4 rocks (same exact thing as the mad rooster it uses a 231 planetary and d300) and I love the gearing options. First (for aw4) is 2.8, Front case is 2.72, rear case is 2:62 (7.12) With 5.38's in the diffs (107:1 in low low is nice in an auto since the torque converter compounds). With 40's and say a 5300rpm redline it will flat out get it up to 57mph in low range. Which makes up for lack of big power.

What's nice is the box 4 rocks is short - only 1 inch longer than a np231 with a sye. And an aw4 is only 25.8" long so it gives you some nice long drivshafts. The front case is very easy to shift in and out while moving. The the planetaries can be upgraded to the 231hd 6 planetary set which is in the big dodges and will handle whatever you throw at it. the d300 isn't as strong as an atlas it doesn't shift as easily. To me running the d300 is affordable the 23 spline outputs I can upgrade later to 32spline and if I bust the case well stak makes a beefy replace a case. All that stuff adds up to close to an atlas but I can upgrade as it comes a long.

 

[Panos]

Rob, I will be running the exact same motor trans combo and this same question has been on my mind since I bought the damn motor about seven months ago. I ended up thinking an atlas with 3.8 or 4.0 would be best.And as low as I could go in the axles, for you 5.38's, for me 5.29's. Keep in mind we are used to using a manuel trans in our toyotas and we are switching to an auto, that meaning we wont need as low a gears as we are used to, not to mention going from a 4 banger tractor motor to a much higher Hp V8 ahhh I cant wait either . it will be fun

 

[Panos]

one more thing, around 100:1 is ideal for your lowest gear in an auto. so I have been told..

 

[I Lean]

one more thing, around 100:1 is ideal for your lowest gear in an auto. so I have been told..

I was completely happy with about 48:1. One of the lower geared auto guys I know of (aside from Atlas 4speeders) is Herzog, with his 4.3 Atlas and AW4. I don't know what axle ratio he had, but let's say 5:38's for sake of argument...that puts him at about 65:1.

100:1 is manual tranny range. (my Toyota with 5.29's and dual 'cases is 108:1...)

 

[Panos]

I was told wrong.. thanks for the real world knowledge.

 

[SUPERFLY]

I believe my green runner is 84:1 in first gear, lowest low range, 410s, dual stock cases. Wow! Great helpful opinions, first hand experience and information! That's a cool site chevycrew. Seems like a lot of people are saying to go as low as you can in the axles? I've always felt like anything lower than 488 would be too low?

 

[Jinx]

Anyone out there running an atlas 4.3 or 3.8? jinx, what axle gears are you running? How fast can you go in 3.8? What motor are you running? I'm leaning toward atlas 4.3 or 3.8 with 4.88s? This way in high range I should have plenty of power as far as tcase goes will 4.3 put me too low? Will 3.8 be low enough?

Let see. I am running a Tune port chev 350 with a 700r4 the 4spd atlas on 40" tires with 4:56s in the axles.

To be honest I am not sure how fast I can run. When I set up the atlas I had them put the port for my variable speed sensor before my t case and did the shorty housing without a speedo to save length. I want to say my 4spd including adapters is only about 4" longer than my Dana 300 was maybe less.

With the 3.06 fist gear for crawling it kind makes up for the 4.56s vs the 2:48 in the th400. The over drive is nice too.

When I am in 3.8 and I feel like my buddies are leaving me I just change to 2.7 and we can fly.

I hope that answers you questions.

 

[Jinx]

One more thing. Find out what ratios other are running you like and build a spread sheet. You will be surprised how close you can get with different trans, t case, axle gear ratios.

 

[Jinx]

I'm running a 6.0 ls2 and a turbo 400

I had a chance about two years ago to try a turnkey 550hp 6.0 ls2 with a hughes built th350. All I can say is SILLY fast. High range 2nd gear was over 100 mph on the dyno.

 

[chadschoon]

I had a chance about two years ago to try a turnkey 550hp 6.0 ls2 with a hughes built th350. All I can say is SILLY fast. High range 2nd gear was over 100 mph on the dyno.

Ya the car I co dawg in (Casey beach's) has a 6.0 with around 500 HP and a turbo 400 but he runs a stack. I think it has 4:88's may be 4:56's but I'm almost positive it's 4:88's and it's pretty fast


Ok really fast!

 

[cjncustoms]

Ya the car I co dawg in (Casey beach's) has a 6.0 with around 500 HO and a turbo 400 but he runs a stack. I think it has 4:88's may be 4:56's but I'm almost positive it's 4:88's and it's pretty fast


Ok really fast!

Isn't Casey running 5:13's chadly? Just curious cause I thought he was...anyways carry on!

 

[chadschoon]

Just confirmed with the beachonator and they are 4:88's

 

[cjncustoms]

Just confirmed with the beachonator and they are 4:88's

Oh ok! I dont know why i thought he was running 5:13's... Anyways robbie what ever you come up with im sure it'll do just fine

 

[SUPERFLY]

I'm thinking atlas 3.8 with 4.88s, strat, is your rig driver drop? Has anyone ran a "box for rocks with an atlas or driver drop atlas for that matter? Back when I was looking at the mad rooster set up it looked like it might have clearancing issues with a driver drop setup???

 

[I Lean]

I'm still saying go deeper than 4.88's (remember, you have overdrive that Casey doesn't). I'm also still saying if you're considering doing a crawl box before the Atlas, just skip it and do the 4speed. (shorter/stronger for the same gear options)

 

[SUPERFLY]

According to chevycrews calculator, it does make way more sense to go lower, but what about strength? Will that make my pinion way weaker?

 

[Gravy]

Mine is driver drop. I don't see an issue with an atlas behind a crawl box because the front output on an atlas is farther from center than a d300.

 

[I Lean]

According to chevycrews calculator, it does make way more sense to go lower, but what about strength? Will that make my pinion way weaker?

Yeah, lower gears will be marginally weaker...but don't worry your pretty little head about it. You won't break 'em.

 

[Gravy]

Yeah, lower gears will be marginally weaker...but don't worry your pretty little head about it. You won't break 'em.

Well its not a toy axle... but have you met ROBBIE? LOL

Well I haven't broken my 5.38's or an axleshaft, and I don't think Casey, Rawlin or anyone else I know has broken a r/p so I think you might be ok

 

[SUPERFLY]

Casey has, as well as several other people I know. How ever I honestly haven't broken any ring and pinions that my awesome gear guy has installed...