Take off in 4-low when pulling heavy?

[chillman88]

no but I did own a petetbilt with a 5speed main and 3 speed auxilary...I liked it better than an air shift trans

This is what I would love to do. I believe @RLDSL is the username of the guy on here with a brownie box behind his ZF5. I'd love to copy his setup someday if I can find a brownie box for a decent price.

 

[madpogue]

agreed with this 100% [strike]Tcase[/strike] 4LO is not "shift on the fly"!

Fixed. Yes, in the context of this thread, it's NOT wise to shift in/out of 4LO while moving. But a t-case that doesn't allow 2HI/4HI shifing while moving is of no use, except perhaps while mudding.

My own experience, the couple times I've tried, is that from 4LO to 4HI, on loose snow, at about 8 MPH, it went in okay. But this was unloaded on level ground. No idea what a load or slope would do. And any 4HI->4LO attempt grinds, even at 1-2 MPH.

 

[mikee]

Shadetreemechani has it right ,use it to get to a better spot,I haul in Tenn. also fun.MY truck trailer eQuipment 32,000lb,had my share of time with TDOT,HA

 

[Black dawg]

Know of a truck here locally that was being used to haul some really heavy scrap loads, they would shift out of low range at 40 ish.... they said it sounded bad, but lasted a couple years doing it. I thought they were FOS with their stories, until I started hearing some second hand info....one load was 110k gross

the 10.25 died in this truck with a stripped pinion gear.

 

[lude and rude]

my take on the subject is, i would rather slip the clutch (a wear item) then take the chance of grenading the transfer case and possible hurting the transmission as well. if your truck isnt setup to haul that heavy then dont do it. get the proper gear to do it the right way.

 

[austin92]

Regearing isn't that bad. I did it for the first time on the 10.25 in my truck. Just had to buy a shop press as far as tools. Spent like 180 on gears, 220 on master install kit, and 585 on a Detroit truetrac


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[AcIdBuRn02ZTS]

The issue with regearing in my case is doing front and rear which would cost more then an under drive unit. As far as stock tires being cheaper... negative. I pay less then $100 each for 80+% tread 37 12.50 16.5 load range Es... (actually just bought another set... gave $360 for 5 shipped to my door).

I haven't hooked a trailer to this truck yet so I honestly don't know how it pulls... but based on how it takes off unloaded, I'd say it'll struggle with a heavy load behind it.

I think I'm going to start researching ZF6 swaps or trying to track down an under drive aux. trans unit.

I want this truck to be able to pull heavy... but I also want it able to make it back down the trail to my broken trail rig and get it out... so street rubber/etc.. is a no go.

Who offers an under-drive unit these days?

 

[79jasper]

Only thing you'll gain with the zf6 is the granny L gear. 1-OD are practically the same as the zf5.
But that may be just what you need.
You can also adapt the nv5500. (Dodge 6 speed)
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[Thewespaul]

gear vendors is the way to go but they are worth their weight in gold and tough to find. Some guys have taken divorced transfer cases and flipped them to use as an overdrive

 

[Dieselcrawler]

Still your best bet with that tire size is regear to 456. I ran a calculator with your truck, on stock size tire (left chart) and on 37's(right chart). Yes it isn't the cheapest but it's the best way.

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[AcIdBuRn02ZTS]

Is that chart on the left with 3.55 rear or 4.10?

I was almost certain I'd need to step up to 4.88 (my truck is currently 4.10)

That is more then likely the route I'll go... just sucks. I'd like to do it myself but buying all the tools for setting up 2 axles is kinda pointless for a one time job. I'll do some calling around and see what I can find.

Thanks for the input.

 

[Dieselcrawler]

Left side is zf5, 4.10 gears with 32's. Right side is zf5, 4.56 gear with 37's

 

[Dieselcrawler]

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Here is 4.10 on left on stock tire, 4.88 on the right with 37's. So either will work. You towing heavy would make me want the 4.88's

 

[Dieselcrawler]

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4.56 on 37 on the left, 4.88 with 37's on the right, just to compare them.

 

[AcIdBuRn02ZTS]

Thanks bud. I'll probably go with 4.88s. Not worried about running over 70 in this truck so a bit higher rpm is fine by me as long as it pulls what I need it to.

Called one local shop and was quoted nearly 1k if I drop the axle off out of the truck. Doing some shopping around at the moment.