Question on running 37's

[72K5er]

I am changing some parts on my K5 and I am thinking of stepping up to 37's. I have a 72 K5 with a 350, 4l60e, np208 drivetrain with a dana 44 front and 12 bolt rear. I have enough lift to easily install the tires and I plan on regearing. Do the axles need to be beefed up to accomadate the bigger tires. I had 35's and it did good. For now the truck is for mainly street but may eventually be used for offroad. I know with Jeeps, people say that alot must be done to run 37's but since this is a full size Chevy I was not sure. Thanks

[onlyifihadachevy]

Well if a jeep needs a lot, then a full body should need more because of power and weight.


If it is for street only then the axles shouldn't be a problem. If you are just trail riding and not to heavy on the trottle then might be a problem but should work for a little. As long as theres no bouncing it should be fine. But if you are going thru mud wide open, hill climbs, or night wheeling then you might have some problems with axle strength.

[71blksuper4x4]

My old 72' had a Dana 44 (3/4 ton) and rear 14 bolt (3/4 ton) and they held up great to mudding and such when I had 37"s on it. Did a little bit of the same with the same axles and 42"s. I wouldn't trust 37"s on half tons if you plan to do some off roading. The front axle would probably be fine, but the weakest point is the rear end. Trevor

[liftmeup]

swap out the wheel studs to some 220,000's You don't want sheared lug suds ,even drill them out and move up a size.

[amullis]

You can run the 37's on your half ton set up. If you do mostly highway driving and the ocasional trail ride you should be O.K. It's really up to how much money you want to spend. The easiest and cheapest way would be to convert your front axle to 8 lug and then find a 14 bolt in the junk yard. I saw 4 or 5 in a local yard about a month ago and the guy said he wanted $125.00 a piece for them.

[litebulblsc]

My dad mudded 1/2 tons with 39.5''

[liftmeup]

"My dad mudded 1/2 tons with 39.5'' I hope most are smarter than that

check out google/youtube for all the broken wheel stud crashes, any racing onroad or off has rules about studs Hell you can't run a truck with 36inch+ tires at the local mud races here because they know what happens when a 40 inch tire thats spinnng 60-70 mph cuts loose. People Die thats pretty much what happens. 35 is the max on 6 lug truck.

[Burt4x4]

I twisted a rear 12bolt with 33s It was all my fault as I was too heavy on the throttle while climbing a hill. It had a freash Auburn Posi in it and I ripped off the driveline at the same time the pumkin tiwsted on the axel tubes. Luckly I had an axel truss on it as that "held" the axle togeather while I drove home in front wheel drive. Most agree that 35" is the max for 1/2ton but if your mostly street then they will last..off road the rules change.
Not much aftermarket beef for a 12bolt but I would look into an axel truss. I ran Con-Ferr on mine..not sure if they are still around or what?
D44 has alot more beef like Axels & ujoints & Warn Prem hubs..
Might be cheeper to get beef from a donor 1ton truck and swap in D60/14FF for max beef
.02c

[70 beast]

id have to agree with Burt. its sometimes easier to buy a junk k30 for the axles and swap those it. those will handle the 37's no problem regardless of if its a street driven rig or trail abuser. you might even be able to put your old axles underneath the k30 and sell it to counter to price of buying it. im running 38s on 3/4 ton axles and am thinking that instead of paying hundreds of dollars to beef up the axle with ctm u joints and chromo shafts, i might as well get a d60 and call it quiets.

[72K5er]

Thanks for the advice. I was 50/50 on the tires. I think I am going to stick with the 35's especially since I will have my wife and kids with me sometimes. Just not worth it. Also cant really afford to beef up or swap out axles right now, I am still crossing my fingers and hoping Obama will send me a stimulus check........

[litebulblsc]

My dad, uncle and there friend all mudded 1/2 chevys with 37'' and taller tires. Only thing to break between all 3 trucks was one front axle shaft.

[liftmeup]

litebulblsc either thats the 3 tuffest 1/2 ton trucks ever built or something. Around here we see people explode dana 60's and upgrade them with chromemoly shafts and such quite often


Please go easy with the language, there really is no need to be arguementative.

[litebulblsc]

But is it just mud bogging? Mud bogging is hell on motors, not necessarily axles.

[onlyifihadachevy]

When you Are mud boggig the motors get used, but the axles/drivelines/tranny eem to get more stress because of traction then no traction, then traction again. The bumps, many things to break axles.

[k14burb]

I've been running 37's on my 1/2 ton burb for a few years now. 10 bolt front, 12 bolt rear. I take it out desert bombing quite often, but nothing too hard core. Sand and some hill climbs. The 454 is plenty stout, but I'm easy on the throttle and just crawl up the hills.

I will upgrade the front to 8 lug, and put a heavier duty rear end under her when money allows. When the 35's I had on it got bad I opted to swap on the 37's from my 3/4 ton burb I was selling rather than by new 35's. So far it's been okay, but I drive it aware of it's limitations.

[OKGMC4]

So if you have a 3/4 ton truck with 8 lug then 35" should be fine? I was thinking staying conservative with a 33 would be the "safe" option because of the dreaded "37 inch rule". Still learning...