38's and 3.54's - need thoughts

["Mad Max"]

... okay, okay... I posted this in the off-road forum too before y'all think I'm looney, read the whole thing



The Truck: '78 Ramcharger (ridiculously modified) - 6BT Cummins, 518, 203/205 doubler, D60/D70, 3. 54's.



Currently I've got 35's, and it was built that way with a big block, 727, and a 205. Worked well enough, but I decided to upgrade to the 6BT, 518, and doubler. So now I've got double the torque and double the gear reduction. With the Cummins I've also now got a heavier truck, to the tune of about 7000 lbs total. And now... the 35x12. 5's are, well,... . small.



I'm getting wider tires either way, but I'm now thinking taller, specifically 38x15. 5/16 (395/70r16) Mickey Thompson Baja Radials. With the 6BT I know the truck won't hate 38's with the 3:54's. My question is... . and please 'dig' my meaning... . will I need to upgrade to 4:10's sooner... . later... ... . or at all????



I'd love to do 4. 10's now, but I need tires now and I'll do gears... if necesary... . later. Can anyone out there in 6BT land give me some 'reasurrance' that, for now, I'll enjoy the 38's for at least one season?



Engine power output will be +/- 300 hp and 600 tq in the end. transmission is fresh with hard core 6BT rebuild (converter, v-body, kit).



Also, my '93 Ram has 3. 54's and 35's and it loves 'em - rolls on 35's with zero effort. transmission has a DTT converter. 38's are a little taller but not a huge jump from 35's, so I know the hole shots may feel a bit slower but I'm guessing with a nice fresh transmission it'll feel purty sweet on the highway, and the highway is one of this rigs' primary play grounds. Add the doubler (4-1 ratio) and I feel it'll crawl pretty good too. It's being built to cruise as easily as it crawls.



Anyone have 3. 54's and running 38's? Got any good info for me?



... . I'm not so crazy after all... ... ... right?



- Sam

 

[EBung]

You answerered your own question I'd love to do 4. 10's now, but I need tires now and I'll do gears... if necesary... . later. You will get by but it will be long legged in OD.

 

[Flexiheep]

Your not crazy Sam I had a friend once with a 401 in a CJ7 with 42 Swampers... . Poor thing had 3. 07 gears for a year or so and could still light them up.



You will want 4. 10 but you will live just fine with 3. 54. Life is about what we have not what we want, so build it with 3. 54 and you will have plenty of fun with it. Plus then you will be that much closer to the megacrew... ..... Oo.

 

[JLEONARD]

Your not crazy Sam

Come on... . we almost had him committed!!!:-laf:-laf

 

[CSchafer]

your good to go I had 39. 5's with 3. 54's. Mine is a stick but could still take off in second easy even with a ceraimic clutch. For off roading your doubler will be more than enough.

 

[Steve Graham]

Do it right and put in 4. 56's, other wise OD is useless.

 

[MChildress]

ditto:4. 56 gears

 

[Simplysmn]

Hey madmax if you want some really nice but heavy tires I can get 325-85R16 michellin's pretty beffy tires and rated for like 5500 per tire thats what i put on my old crewcab before I sold it but I also had 411 gears maybe the 354's will be to much ?

 

[klaybus]

Mines a 2nd gen but 4. 10s we're a huge improvement over the 3. 5s especially if you tow fwiw.



Clay

 

[Moab4x4]

After watching the build, seeing the RC and knowing your stated uses of it, keep the 3. 54's. It's not the tow vehicle.



My gear ratio calculations and arguments are posted in the offroad post https://www.turbodieselregister.com...54-s-38-s-need-some-thoughts.html#post1946273