The Stovebolt Site Forums The Shop Area Driveline 3:42's or 3:31's (1949 3600 original 4:10 axle)

49 3600 original 4:10 axle. 235 & 4 on the floor. need highway friendly gear. switch to 8.5 10 bolt 2nd gen camaro/firebird? mounts line up nice w/ leaf springs?
3:31's enough grunt wo/ giving clutch work out?
I'd keep original axle (hucks, lever action shocks n' all) but can't find gears.

new member, 1st post, hi! thx

A stock 1949 Chevrolet 3600 (3/4 ton) would have left the factory with a 4.57:1 rear end. Similar GMCs were equipped with either a 4.57 (most) or 5.14 gearset. There were drop in center sections with ratios at 3.73:1 used in V8 big block powered Chevy and GMC vans in the late 60s and early 70s (I may be off a little on the years), but they are made of unobtainium.

I have late 60's GM car rear axle in my '52 GMC 3/4 ton with a 3.55:1 ratio. I certainly don't have to worry about whiplash, but I haven't blown the clutch out of it in the 11+ years and 40K+ miles I've been driving it.

Fit any Dana Type 60 rear axle from a Ford, Dodge, International, or GMC 3/4 ton. It's a pretty simple conversion, uses Bendix drum brakes, and there are at least half a dozen suitable gear ratios in the mid to high 3.XX:1 ratios available. The original looking 8 bolt wheels are also a bolt-on fit, and you can still do real truck stuff. Thanks to round track racers, rock climbers, and drag racers, every high performance gear manufacturer on the planet sells gears, bearings, and installation kits.
Jerry

*Before* you do *anything* you should read our Tech Tip on axle upgrades for 3/4 and 1-ton Advance Design trucks...

My guess is that you'll come back with some different questions ...

And welcome to Stovebolt!!

John

did'nt think of a dana 60. 3:54's would work and keep original 8 lug wheels/hub caps
do they even make 5 lug original looking wheels that hub caps would fit?

Helloooooooo.... READ THE TECH TIP. You are over thinking all of this.

Jerry -- If he put a modern Dana 60 back there, wouldn't it be too wide? He'd have to relocate spring perches and his wheels would stick out from the fenders ... ???

I would think finding the 4.11 ratio third member from a '68-'72 3/4 ton HO52 would be the far simpler solution. I find the HO52/72 with the 4.11 gearing, coupled to either a 235 or 261, and running 17-inch wheels to be perfectly capable of highway driving/modern traffic. Not sure what the 15-inch wheels do to the mix, but my truck does great. I would be afraid of the 3.xx gearing being a touch on the tall side ... But what do I know?

I'm presently running a 4.57 on 265/75x16 tires with a 17% overdrive and even in direct drive I have no trouble keeping up with freeway traffic at 60+ MPH. I have had 255/85x16 tires in the past. They're about the same diameter that the factory option 7.50x17 tires of the day. Those were installed on 1-tons with 5.13 axle as standard but that setup was optional on the 3/4-tons. If by some stroke of luck, you have a 4.10 axle , I'd leave it alone. Even with a 5.13 axle and 750x17 tires you're turning 3300 RPM at 60, which was the rated RPM for max horsepower for the original 216. It's noisy at that RPM but won't hurt anything. With the 15 inch tires the 3/4 tons were pretty slow with a 4.57 axle. But big tires should get you about 10 mph. Mine turns 2750 at 60 in direct with the 265/75 tires, which are the same diameter as 235/85 tires which might be more appropriate for a 3/4 ton.

One reason to hunt up a later axle it to get away from the Huck brakes. Mind you, there is nothing inherently wrong with Huck brakes,it's just that you can't get drums. After 52, the 1-tons came with Bendix brakes. The 3/4 tons might have change a year earlier, I don't remember. Swapping to a corporate 14-bolt axle is an option (see Greg's treatise in the 1-ton and big bolt sections) but it's enough extra work that I haven't gone that route as my rear drums are fine so far. These days, though, these parts are rare in bone yards.

you're right Bill- i have stock 4.57:1 and she winds up quick.
4:11 from 68-72 still too steep for me.
don't wanna go t5 route.
looked at a 49" 3800 with full floating 14 bolt-looked good
and he told me it still had "split rims"
so no bolt in dana 60 with 3:54 gears i can pick up at the yard? lol

John, I'd just narrow the Dana 60 by a few inches to match the original spring width, and shorten the drive axles- - - -just like we did on the dirt track cars. Of course, if the rear axle happens to come from a "cab and chassis" made for a small delivery van instead of a pickup or another type of vehicle, it's going to be narrower than usual, and might possibly be used without any alterations. If he's running a flat bed instead of a pickup bed, a little extra width won't be a problem. A 3.73 gear, or maybe a 3.90 would work well- - - -or at least the Dana 60 with the 3.73 gears brought my 59 Suburban all the way from California to Tennessee without a hiccup- - - -loaded to the roof and towing another vehicle.

We'll let the gentleman discover that he's WAAAAAAYYYYYY over geared for a 235 on his own, with anything in the 3.50'ish range. He's going to be "rowing it with the shift lever" downshifting at every hill.
Jerry

Tommy -- Good points! The cool thing is he can swap in both the 3rd member (4.11 gears) from the newer HO-52/72 as well as the Bendix brakes -- it's a bolt in replacement from the backing plates out. But as I have found, living with Huck brakes isn't a huge deal -- you just have to drive conservatively and learn how to adjust them every year or so ... And if you put your ear to the rail, you can pick up drums from folks who are swapping out to other other options ... if you are willing to take entire axles off their hands. I have several sets of brake drums in my stash that way.

Another thing to keep in mind, and Jerry and the other gray beards can back me up, is a way to extend the life of those precious Huck drums -- don't get them turned every time you do the brakes. Maybe just take the outer ridges off, but grooves are ok as long as the drums aren't out of round. Grooves actually increase the braking surface, too

Jerry -- Ah ... "just narrow the Dana 60 by a few inches" ... you make it sound sooooo simple ...

69 coupe -- not sure what you mean by the 4.11 being too steep and winding up too quick. I'm running the 4.11 gear set in my truck (261, SM-420 and the original 17-inch multi-piece wheels with bias ply tires) and it is nearly a perfect set up for my truck. Good in traffic and cruises comfortably on the Interstate at 65 MPH. If you're running a 235, you should get similar performance, especially with the wheel/tire set up that Tommy describes.
??

LOL- - - - -you mean it won't shrink if I wash it with really hot water?
Jerry

Hi John- so when you're running down the road at 65 mph w/ 4:11's and 17" wheels your engine is'nt spinning at 3000 rpm plus?
i'd like to have rpm's in the 2500 range at that speed.
i had a 70 barracuda when i was a kid that had a 440 and 3:23:1 gears (auto) and it was 3300 rpm at 65 mph but it had 15" wheels.

[John should be answering your question but *I* wanted to let you know that you are now past "moderated" status. So from here out, your posts will go thru without needing approval. Plus, you'll be able to do Private Messages (PMs) ... you have them already in your PM box but NOW you can reply to them. ]

69 Coupe

I don't have a tach so I don't know what my RPM's are. I do know, however, that its far from red lining. It sounds/feels like 63 - 65 is a comfortable spot. It's not howling or wound out. And with a little more throttle, it easily accelerates past 70 MPH. *I* do not enjoy the 70-plus experience, but the aural and tactile feedback the engine gives me indicates it can cruise all day at 63-65 mph. And I have had it there many times now on 3-4 hour trips that include Interstate Highway System travel.

Hopefully, some of the other crew around here who are running similar set ups can give you a better answer on the RPM's at 65 MPH. Maybe even Jerry -- he's ridden in my truck and pretty much did the rebuild on the 261.

Hope that helps,
John

Oh, and for what its worth ... While I'm no expert in these matters (like most here), I am a professional truck driver (low boys, RGN's, etc). I learned on a '72 GMC 9500 with a 5=2 behind a 6-71 Detroit ( ). I have a pretty good idea of what a wound out engine sounds like. And I'm not hearing one when driving my '49 at 65 MPH.



As the stockbrokers say, though -- My past experience does not guarantee your future performance ...

My truck is 100% stock 216, 3 spd, 4.11:1 rear end and I drive it every week on the interstate at around 60mph. No problems and no sounds indicating that the engine is going to blow itself up.

235 and 261 engines both run the same crankshaft, and very similar connecting rods and rod bearings. As long as the oil clearance on the rods is close to the minimum specification (,0015") the engine will live happily at 3K RPM- - - -all day at full throttle, pulling a maximum gross weight load (or a big overload, which is what these engines did when they earned their keep as daily drivers). That's considerably more revs than 90%+ of the restored trucks of today ever see. With a little weight matching of the rods and pistons, stovebolts are capable of 4K RPM with no damage. Most people are just too timid to use those engine speeds frequently, if ever. The fan blades are the source of most of the engine noise- - - -pull the fan off and run a few miles at highway speed- - - -you'll be impressed at how quiet the engine actually is.
Jerry

thx for replies guys, good stuff.
it's actually my wifes truck so i'm trying to make it modern & smooth as possible. daily if she wants to.
of course that includes:
12v, electronic ignition, electric fuel pump, pvc, 3 point seat belts, turn signal/tail lights,
usb radio/antenna, gas shocks, hucks? etc, etc, lol!
they make 3:55's for a torque tube but it's not a 1/2 ton.
Jason

i ended up not buying the 3600 49' & got a 53' 3100. original torque tube-3 on the tree.
i'm gonna put in a colorado (6 lug) 3:73 open and a t5.

With that setup, I'll be surprised if you ever get to use 5th. gear except when running downhill. A 216 simply doesn't have enough torque for an overdrive top gear paired up with a 3.73. You'll be lugged down with the power valve in the carburetor wide open, at <10 MPG all the time
Jerry

John,
What is your tire height on Charlie?

Carl -- Don't know off hand. I can go measure it tomorrow. The tires are 7.50 - 17's if that helps...

my truck has a 1955 235 ci motor
block no. 3836233
123 hp
still won't be able to use 5th?

What axle ratio and what tire height are you planning on?

235/75/15 tires
3.73 rear axle ratio

That should work for you, especially if your 5th gear is .86 overdrive. I am assuming that your tire height is close to 28"

Carl -- My tires look to be 33-34 inches in diameter

That is why you have no need to put a T-5 in Charlie to comfortably go highway speeds with 4.11 rear gears. I could feel that in the seat of the pants when I rode in it with you at Wrenchfest.

T-5's are like Jeeps -- for girls

I like girls, except for icky ones...
If my 3100 had come with a 261 and 33-34" tires and a 4 speed, I wouldn't see a need for a T-5 either.
But alas, all I have is an itty bitty truck with a puny 235, so I went with a T-5 and a limited slip rear axle.
We need to set up a Race Day.

Well this is my wife’s truck-I’m just the mechanic-lol

What’s nice about a pre 93 s10 5t is I can use my original bell housing, pressure plate, flywheel, clutch fork and throw out bearing, just need a 14 spline clutch disk