low rear end ratio's....where at? 3.07/3.23 etc

[hcaz095]

I am looking at doing a diesel conversion in the future... Due to the low rpm's of diesels, I would need a low ratio rear end, which is somewhat uncommon in these years trucks. Since I would be re-doing the drivetrain anyways (engine/trans) I would need a new driveshaft length, so the rear-end is not that big of an issue. What other options do I have for a regular width rear axle? preferably with rear disk brakes. Any info is appreciated. I am not sure on power, but options for low power(cummins b3.3t), or rear ends that will hold up to the torque of a 6bt. Thanks for the input.

~Zach

[Longhorn Man]

actually, you'd be wanting a high gear, not a low gear.
Are you looking at doing a 3/4 ton, or a 1/2 ton truck?

[hcaz095]

Depending on what truck I picked up.... I would definately be a 2wd....


1971-72 SWB 1/2 ton... I am leaning towards this for looks, parts availability, more of them around etc... with the b3.3t or qsb3.3 as it is only 550lbs, about the same as a 350/396. you can get them at 100hp/300 ft-lbs.... more than enough to drive around, although I wouldn't be smoking the tires anytime soon.


Or a c/20 longhorn due to the 8.5 ft bed... I have a few motorcycles, and a 30ft sailboat (only 4000lbs), where the 4bt or even a 6bt is an option, but the 4bt is ~760lbs so it is already getting a bit heavy esp with the 900+lb 6bt.

Thinking about diesel conversions is always a great thing, but the cost to convert is a super long payoff, so the 5.3efi always looks good, but its not capable of running svo no matter what you do...

~Zach

[Old Yeller 1970]

Old Yeller and the '71 donor I used to swap out the brakes and rear end both came with 3.07's. I don't think they are that hard to find.

[67_C-30]

As Andy said, it would depend on whether it is a 1/2 ton or 3/4 - 1 ton. I put a turbocharged low-mileage 6.2L CUCV takeout diesel in my '67 C-30, but since it is a 1 ton, I upgraded to a 14 bolt, which is plenty adequate. I have a slighty turned up DB2 4911 injection pump (which is the hottest mechanical pump available for 6.2/6.5's), I added a stud girdle to strengthen the bottom end and ARP head bolts, and I plan to run 10 - 12 psi boost. That is about the max amount you can run on these engines with without lowering compression ratio. They will produce between around 215 - 225 HP and around 440 - 450 TQ tuned this way. In stock form without the turbo and 4911 IP, the CUCV J code engines are rated at 155HP and 250 TQ. I considered a Cummins 4-BT swap but they are very noisy and vibrate badly. I also thought about a 6-AT since they shorter than a 6-BT. I even considered 3-53, 4-53 and 6V-53 Detroits, but in the end, the 6.2L swap was the easiest since it was a direct bolt in, and had the correct pattern for my transmission. The Detroits are still the sweetest sounding diesels ever built though, IMO! I'm running a NP-435 4 speed as of now the 14 bolt has 4.10's in it. I'm going to swap them to either 3.42's or maybe even 3.21's to make it better out on the road. I had a 6.2L in a '84 K-10 with 3.08's and it towed out on the road better than a '83 C-20 with 4.10's that I had at the same time. Both were automatics, and the 4.10 geared truck took off a little better, but it struggled on hills out on the interstate worse than the 3.08 geared truck. The 4.10's put it so far above its torque peak at 70-75 mph that it towed better, slower in high gear. That being said, I'm not afraid to go that high with my '67 C-30 since the NP-435 will have no issues taking off.