So yesterday, as I was driving home, I noticed a new clunking sound coming from my 1988 GMC Sierra 4x4 half-ton rear differential. This morning I jack it up and took the cover off and noticed that half of one of the teeth have broken off of the pinion gear and another tooth next to it is cracked. I want this truck to have the ability pull a 29 foot fifth wheel trailer once in a great while around town. So my question is, do I want to upgrade the axle to a three-quarter ton axle, or should I install a different ratio pinion and ring gear set? (eg. 3.42 to a 4.11) If I upgrade the axle, which axles will be compatible with my truck? I understand that I would have to shorten my drive shaft since the nose of the differential would actually be longer if I upgrade to the three quarter ton, but could I just use a drive shaft out of a three quarter ton truck instead? Also, if I change the rear end ratio, well I also have to change the ratio up front since this is a 4x4? Obviously, expenses are a major factor in my decision, so I need to know roughly what to expect with both options. Thank you in advance for any help

 

Well the key detail here is how heavy will this 29ft trailer be? Tongue weight? hydraulic or electric brakes? All things I would consider before I ever think of taking a 1/2 ton and think about doing heavy duty things.

Personally, I'm a believer of using 'too much truck for the job'. I'd just get a 3/4 ton. If that's not an option, I'd get an axle and leafsprings from a 3/4 ton, and swap it all over. If the driveshaft from the 3/4 ton donor truck doesn't fit, get everything all installed and drop it off at a driveshaft shop.

But yes, if you change the ratio in the rear, you'll most definitely want to change the ratio in the front axle. If you don't, you will end up with a "Push/pull" problem in your drivetrain. The only way you can get away with having different size gears in the front and rear is if you're on a surface where you have almost no traction for your axles even have the possibility of binding.

 

I definitely agree with NullHead.. I would consider moving up to a 3/4 truck for pulling your 29ft trailer