373 swap to 410 or 456

[chris989]

Hello all,

1996 burb 454, 4l80, 265/75/16.. all stock

The truck runs great and tows well. We are towing ~6000 and cover a lot of mountainous states. I would like the lower gear and generally do not tow above 65mph.

Question.
Has anyone gone to the 456 gears?
the L29 torque peaks at ~3200 rpm, what might be the final rpm at 65?
was it a positive or negative in the end?

I know the 410 will work well but thinking the lower gear will help even more considering speed is not the goal.

Thanks in advance,
Chris

[Blue97]

Im looking forward to seeing some responses, I also want to re-gear.....

[chris989]

Originally Posted by Blue97

Im looking forward to seeing some responses, I also want to re-gear.....

What are you running now?

[Blue97]

Originally Posted by chris989

What are you running now?

97 silverado C1500 ECSB 5.7 with 3:73 gears and 33" tires .

[LynnJr]

http://www.ramblerman.com/blazer/gearcalc.htm

[68Timber]

I had a 99 C2500 that I swapped the 3.73's out for 4.56's and it worked great. Mine was a 5.7 truck. I did have to take it to the dealership to get it programmed for the gears to correct the speedometer.

[chris989]

Originally Posted by Blue97

Im looking forward to seeing some responses, I also want to re-gear.....

Blue,

I just finished a 2500 mile trip and I am now thinking i might just stay with the 373.

What i find is when pulling a hill, (6000# trailer < 7% grade) I downshift to third and the RPMs are 2900 @ ~60mph which is right about the height of the torque curve. I had a few issues with my crank position sensor before and now that that is fixed the truck pulls much better.

I do have a donor K3500 now that has 411s in it. not sure if i want to go through the labor of the swap though.

[Blue97]

Originally Posted by chris989

Blue,

I just finished a 2500 mile trip and I am now thinking i might just stay with the 373.

What i find is when pulling a hill, (6000# trailer < 7% grade) I downshift to third and the RPMs are 2900 @ ~60mph which is right about the height of the torque curve. I had a few issues with my crank position sensor before and now that that is fixed the truck pulls much better.

I do have a donor K3500 now that has 411s in it. not sure if i want to go through the labor of the swap though.

I have to drive around town in 3rd gear just to stay out of Overdrive unless I hit the Highway.... I think im just going to drop the truck and get a BB tune.

that should make it a fun ride

[chris989]

Originally Posted by Blue97

I have to drive around town in 3rd gear just to stay out of Overdrive unless I hit the Highway.... I think im just going to drop the truck and get a BB tune.

that should make it a fun ride

I have an 89 5.7 tbi and it ha 373 with 33"bfg. If is way to high a gear. In that truck i might go to 4.88 but at least 456. I have a 4l80 trans to swap in so the steep gear will help it a lot.

[Blue97]

Originally Posted by chris989

I have an 89 5.7 tbi and it ha 373 with 33"bfg. If is way to high a gear. In that truck i might go to 4.88 but at least 456. I have a 4l80 trans to swap in so the steep gear will help it a lot.

I was thinking of 4.56 gears and a trutrac diff , the only problem I have is I don't trust ANY shops in my area to do the work..

I thought about going to the dealership , but I would have to bring my own jar of K/Y.......because its gonna hurt

[chris989]

Originally Posted by Blue97

I was thinking of 4.56 gears and a trutrac diff , the only problem I have is I don't trust ANY shops in my area to do the work..

I thought about going to the dealership , but I would have to bring my own jar of K/Y.......because its gonna hurt

I am in vegas, not to far from you, I have used Adams Driveshaft for almost 20 years. They are in Henderson, the southeast end of the valley. They are honest and they know what they are doing.

[b454rat]

I had a 97 k2500 that had the 454, 4L80 and 4.10s with 265/75s. I towed a RCSB on a tow dolly, with a Dana 60 front, 2 454s, a welder and who knows what else in the back of the 97 with the cruise set at 70, and there is some pretty decent hills on RT81, it never dropped below 70. 350+ miles and used a tank of gas.

[BigBlocksRule]

Forget swapping gears, swap out the complete rearend. Find a 14-bolt semi-floater with 3.73's. Pop the cover and check gears, swap pinion and axle seals, fill 'er up with your favorite diff juice and you'll be good to go. Complete rearends around here go for $250. They're close to indestructible and even the factory gov-lock works well in the bigger rearend.

[Cabnchassis]

Originally Posted by BigBlocksRule

Forget swapping gears, swap out the complete rearend. Find a 14-bolt semi-floater with 3.73's. Pop the cover and check gears, swap pinion and axle seals, fill 'er up with your favorite diff juice and you'll be good to go. Complete rearends around here go for $250. They're close to indestructible and even the factory gov-lock works well in the bigger rearend.

I can't think of one good reason in the world to swap a 14ff which his burb most likely would have come with stock for a 14 bolt sf unless you have to have the ground clearance. I have both and while I don't have any problems with the 14sf or the eaton locker, I wouldn't put one in a truck on purpose. It's got way to many extra moving parts. I've seen one throw an exploded bearing race right through the diff cover when it failed, they don't go quietly when they go. Also most of them are limited slip and require limited slip specific gear oil.

My k2500 has 4:10s and I have no complaints. Mine is a 5.7 and you don't notice it's such a dog with those lower gears. Only gets maybe 14 hwy at best though and about 8-9 around town. With a big block i doubt fuel mileage was your worry anyway but you'll lose some doing the swap.

Should you want to swap axles (it will be cheaper but quality is obviously unknown) look at the 3/4 ton burbs from the 90s you should be able to find a 14 bolt ff single rear wheel in 4.10 with no problem, most big block/6.5 burbs I see at the wrecking yard have that dif setup.