Gearing or rear end swap?

[extremesounds13]

I have a 67 3/4 ton burb that had a blown up 327 and a bad turbo 400 in it when I got it a couple years ago, long story short I swapped in a 454 and had the T400 rebuilt, I've been driving the burb for about a year and a half but I don't drive it as much as I like because at 55 mph it is pretty wound up, I can push it to 65 mph but I don't want to hold it there by any means. I'm getting it painted right now and want to drive it more when it's done. I feel like the rear end is at least 4.11 maybe 4.56, I want to either get different gears or swap the rear end out. Which is easier, and less costly? It's an eight lug so what years do I need to look for, for gears or complete rear end?

[LockDoc]

-
The first thing you need to do is find out for sure what is in it now. Check this thread for tips on how to find out what your current ratio is.

http://67-72chevytrucks.com/vboard/s...d.php?t=578793

Is it a coil or leaf spring rear end?

LockDoc

[extremesounds13]

Thanks I'll see if I can find out whats in it. It is a coil rear end.

[68 TT]

Most likely you have the Eaton HO52/HO72 rear end with 4.57 gears or worse. 4.10's are out there for them but are not inexpensive. I see the used 4.10 gears on an open carrier sell for $100 on a regular basis.

It is possible you have the Dana 60 rear end too which is far easier to get parts and gearing for.

I chose to put a 14-bolt from a square body into my old leaf spring 69 C20 to replace the damaged 4.88 geared HO72 that was in it rather than pay the $$$ to repair & rebuild the HO72 plus change the gearing. Far less money, easy to come by and just as tough if not tougher.

I am probably going to do the same swap to my new 68 C20 that has trailing arms. I know captain fab makes trailing arm mount perches to fit the 14-bolt housings so all you really need to do is figure out the panhard bar mount. Probably use the old weld on bar mount from the old HO72 housing so all the parts are stock. I guess if you are cutting off the panhard bar mount you could cut off the trailing arm mount perches too and modify them to fit the 14-bolt axle tubes. I am assuming that since he makes the brackets that the axle tubes are different diameters. Don't know for sure.

[68 TT]

Originally Posted by extremesounds13

Thanks I'll see if I can find out whats in it. It is a coil rear end.

Take a picture of the back of the housing and we can tell you if it is the Eaton rear end or the Dana 60. Either of them could be in there or have been put in there in the past 45 years. Makes a big impact upon your decision.

[capev86]

put 4.10 gears in my 72 Suburban C20 (Ho52) and it works great with the original 307 (Q-jet swap) and 3 on the tree. I still need to get my borg warner overdrive equipped 7 bolt saginaw installed for those long highway drives. comfortable cruising speed right now is about 50mph and i can get 15-16mpg on a long steady trip.

[Alex V.]

With the big block I'm sure your Suburban would pull itself along nicely with 3.73's (as long as the tire size is close to stock), but IMHO 4.10 is a very good all-purpose gear ratio. I have an '85 C3500 w/454, TH400, 14 bolt w/4.10's, and it doesn't lack anything down low yet is comfortable at 60-65 - when I get to 70 or higher you can tell everything underneath is humming pretty good, but its power peak is between 50 and 65. Now, the stock tire size on my truck is 32" diameter so that's a pretty tall tire to start with, but your 3/4 'Burb may have tall tires as well. If your rig has anything lower than 4.10's they need to change to be practical on the highway, but if it's 4.10's and you have a 31" or taller tire I think you'd be hard pressed to find a better combo unless you need to sustain more than 65 on the highway.

Note: My dad bought an '86 K20 new - 350/TH400, C6P heavy-duty package w/4.10 gears, and the engine now has 361,000 on it with no bottom end work, only two valve jobs. A good portion of those miles were towing substantial loads at highway speeds (55-65) and the engine is still not in need of a full rebuild. So I think that goes to show that sustained high(er) RPM's aren't always what kills an engine.

[extremesounds13]

Thanks for the replies, I want to swap either the rear end or the gears I need to get to a lower RPM and better mileage is always a plus. I went down to the body shop and snapped a pic or two of the rear end so I will post them, but they aren't very good.

[capev86]

a Dana 60 or newer 14 bolt with 3.54 gears would be a good compromise gear. the 2000 and up 14 bolts feature 11.5 inch ring gears and disc brakes. at 60 your rpm's would be around 2600 (or just above 1800 w a .7 overdrive)


lower rpm's not only reduce engine wear and fuel consumption, but also makes for a quieter ride. glad i swapped the original 4.57 gears for 4.10's. but i'm still turning 3k at 60mph which is way too fast even for that little short stroke 307. the stout gearing is good around town and will be needed when towing 6,000 pounds of 1971 Holiday Trav'ler. but i still want to get my overdrive equipped 3OTT installed one of these days. with a 2.87:1 effective ratio in o\d (2100 rpm at 60mph) i should still be able to tow at reasonable speeds (55-60mph) on level roads and just shift down on the hills.

[extremesounds13]

Best I could get, sorry.

[extremesounds13]

Another one...

[vectorit]

That appears to be an Eaton H052.

Best thing in my mind at this point, strictly thinking along the budget lines.

Determine what gear ratio your Eaton is currently running.
If it is 4.57, then you can search for a 4.10 3rd member in the classifieds.
Swapping out the 3rd member is very straight forward.

I am getting ready to swap my 4.57 3rd for a 4.10 3rd I found on CL for 30 bucks.

I just searched for a while on CL for axles out of 67/72, once I found one listed it just said "3/4 ton axle out of 1970 PU".

I called, and asked him to describe the axle to me. From what he told me, it was an Eaton. Went to his house, and he wanted 100 for the whole thing.
I told him all I needed was the 3rd, and he said OK for 30.00 bucks I can have it. He just said that he was going to scrap it anyways.

For the price, I didn't waste any time getting it home.
I figured I had a 50/50 chance it was going to be a 4.10 ratio, and after counting the pinion and ring gear teeth it is a 4.10.

If you do score one like that, ask for the axle shafts so that they are matched (I was able to get the 3rd and the 2 axle shafts for 30 bucks).

If you are in a hurry, and not having any luck in locating a scrapped Eaton. Then I would recommend finding a Dana 60, since there are more options for gear sets on the Dana 60.
The next choice is a Corp. 14 bolt axle, which is very common these days.
The 14 bolt will afford you choices for ring and pinion sets in a more highway friendly ratio as well.

Swapping the axle is easy too, but there are a lot of little things you will have to pay attention to as compared to finding a 4.10 3rd for your Eaton.
Such things as welding on new spring perches and shock mounts, break lines, E brake cabling, drive shaft, and the pinion yoke.
All those little things add up in time, and little part expenses.

Finally, if you do go to a newer axle. Chances are you will get the larger diameter lug studs, since the earlier studs are smaller. That will mean that you will have to buy new lug nuts that are flared, this is so that they will seat properly on your existing wheels

Just my .02

[72MARIO]

have you considered a Gear Vendors OD unit ?

[extremesounds13]

Originally Posted by 72MARIO

have you considered a Gear Vendors OD unit ?

I would love one but they are expensive!!!

[extremesounds13]

Vectorit, thank you for the info, a lot of good information to think about there.

[capev86]

If I was going to swap axles, I'd find a 2000+ GM truck with the 11.5 inch ring gear 14 bolt and disc brakes with 3.73 gears. I'd also adapt the front brake setup if I had a 67 like you.

Start with the 4.10 swap and then look into an overdrive trans down the road. That really is the only way to go to have your cake and eat it too!

[71K20chevy]

Originally Posted by capev86

Start with the 4.10 swap and then look into an overdrive trans down the road. That really is the only way to go to have your cake and eat it too!

Not to mention if you swap in a 700r4 with the 3.06 first gear, you'd get better acceleration compared to the TH400's 2.48 first gear. Most people seem to say 3.73's are the best compromise, but keep in mind that these trucks, no matter what will be gas hogs. Might as well enjoy them since we only live once.

[LockDoc]

-
I put a 3.07 in the White '67 with a 454 and TH400 and I was really happy with it. It ran down the road great and didn't have any low end problems. That's the way I would go.

LockDoc

[extremesounds13]

Could I find a 3.07 to swap into my axle, or would it be a complete axle swap?

[Bigdav160]

As Vectorit mentioned, your Eaton axle only came with 4.10:1 or 4.56:1 gear set. There is no aftermarket support.

You'll have to change the entire axle out to another type (brand) to get any gear ratio selection. This might mean an aftermarket solution to the panhard bar setup also