anyone running a sm465 with 3.08's?

[no1udknow]

Hey guys, I was looking at gear ratios today, I want to do a manual conversion on the 68 but it seems difficult to find A.) a good 5 speed, or B.) a t56 for a reasonable price. But I have found many sm465's and I was looking at the 1.0/1 4th gear ratio coupled with a 3.08 final gear and 275/60/15's (26.99 height) and it puts the engine at about 2500 rpm at 65 mph.

Was wondering if anyone is running this setup and how do you like it?

[JJR]

Can't speak specifically to the SM465 but my 70 C10 is a manual 3-speed with a 3.07 gear and I have 30x9.50-15's (29.5 height). 2nd gear in the SM465 is close to that of the 3-speed. When towing, I have to feather the clutch to get going good but you would not have that problem with the 6.55:1 granny gear on the SM465. I do like that my truck can do highway speeds without straining the engine. Of course, you won't be doing any speed shifting with the SM465.

[SS Tim]

On a 68 C10/327/CH465 the factory ratio was 3.07.

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[WIDESIDE72]

I dont see why the sm465 and 3.08 wouldnt work. In trucks my dad had in the past, (one tons with steel welding beds, lincoln 200 amp welding machine, cutting rig and tools, he never used granny low unless towing. Granted they had 454's, but I also had a 1/2 ton gmc with a 250 6 cylinder and 3ott. I swapped the 3.73 for a 3.07 rear. Made it a lot more driveable on the highway. I never towed anything bigger than a 16' aluminum flat bottom boat with a 70hp outboard but it did fine.

IMO unless you are doing some heavy towing, the granny low will make up for the 3.08 gear.

[no1udknow]

i'm just looking at options because currently I'm running a th350 with 3.73 and 275/60/15's and my truck is screaming at 60mph. Did th350's come with different gear ratios? Only reason I ask is that when I'm cruising aroud 60mph (i'm guessing judging by the pace of all the other cars around me on a 2 lane rd) my speedo reads about 80/90 mph and my engine is running probably around 3000-3500 rpms. I am hearing the shift into third, but it just seems odd.

[no1udknow]

well, after looking at the ratios, it would be the same as the sm465 with a final gear ratio of 1.0:1. so i guess I need to start looking into a 5 speed o/d trans or a 700r4. My problem is my engine makes close to 400hp and everyone tells me I will smoke most 700r4's and t5's

[leftybass209]

There are no junkyard trans that will handle that kind of power for very long so you'll have to look at rebuilt. Bowtie overdrives claims their level 2 700r4 will handle 450 hp/tq and upwards of 600 on their level 3. I'm sure many re builders can get a 700 behind your engine to comfortably handle that power.

[JGray]

Years ago, I had a 72 K10 with a 350, SM465 and 3.08 gears. I felt I had to slip the clutch more than I liked with a 2nd gear start and it was kind of a pain going into low for every start (driving in traffic). I also had to downshift into 3rd on more hills than I'd have liked to. Granted, this was a fairly stock motor and probably a bit tired as well, and was running 32" tires. I currently have a 72 K10 (different truck) with a mild 350, SM465 and 3.73 gears and am much happier with the combination. With 400 hp and 27" tires, yours may be an entirely different beast...

[Mike C]

My Jimmy had the SM465 and 3.07 in it with a 350. It was a great combo with the stock motor and 28" tall tires.

I went to 33's and it was OK, but when the original 350 expired and I swapped in my 331 with 228 @ .050 cam, not so much. I went to 35's and 4.10s which is almost the same as the 3.07 and 28's.

But the best mod I did was ditching the cam. The SM465 is a great truck transmission with a truck motor. The Crane 266 that's in it now has just about the perfect power band for the transmission. It's 210 @ .050 and I think that up to 216 @ .050 with a 350 ci motor or bigger will be fine.

How much cam is in your 400 hp motor?

[no1udknow]

The motor was built before I got the truck but I have the box from the Elgin can and it says .320 cam lift in/ex, .480 valve lift in/ex , lobe centers 107 in. 111ex, 292 adv duration in/ex, .050 dur = 230 in/ex

On top of that, the engine has 202 heads that are ported with enlarged valves ( I don't know how big) . The cylinders have been bored .080 over (364 ci) and it is running a eddy torker with an eddy 750cfm.

I was told by the machine shop where it was built that it was designed to run a tunnel ram with 2 4bbls or 3 dueces setup to get a little more out of it. But whith the torker and the 750 it should make between 380 and 400bhp

[Scott Liggett]

I am planning to go the other way. My '67 GMC has the SM420 with a Dana 44 3.54 gears. I am changing it to an A833OD that were used in GM trucks and vans in the '80s. It's gearing is 3.06, 1.82, 1.0, .74, just like the 700R4, but I get the fun of the third pedal. I already have all the parts and will be moving the engine to the V8 position when I make the change. The truck was originally a sixer, so the 350 is wedged up against the firewall.

[Maxxd07]

Dads old 79 1/2ton 4x4 came factory with 2.76 gears, a sm465 and a 350. We used to pull a bumper wiper stock trailer frequently with it. Used to have to shift down in the hills but it worked fine. Stock 235/75/15 tires. I really noticed a lack of power when I put a 4 inch lift and 33" tires on it and drove it to college. We didn't know the gear ratio until I wiped out the rear end on one of the trips to school and read the gears during an over haul and a regear to 3.73s. Had to get the custom thick gear since the carrier is only good from 2.76s to 3.55s or something like that. All I can say is that a 2.76 pinion gear is insanely huge! Driving it in stock form it was fine and made a nice cruise around truck. You could start out in 2nd if you revved it a bit but starting in 1st (or low) was just fine. We even have had the front axle chained up with the stock trailer in tow rescuing calves during the blizzard of 97 and still didn't need 4 low. For a 2wd I think the 3.08s would be just fine.

[Mike C]

My own experience is that's too much cam, but your 30 cubic inch motor will certainly help. You just had to wind it up too much to keep it in the torque spread with my motor.