Okay, I'm at the point where I need to decide on a ****** now. I've got a 59 Pontiac 389. It has the manual bellhousing/plate/flywheel, so I can run a manual ******. I've also got a 68-72 GM 10 bolt 2.56 ratio posi rear end to go on the other end. Which ****** should I sandwich into here? I'm more into cruising, but I wouldn't mind something that can get up and go when I want it to. Also, the rear wheels will *likely* be 30" profiles. This is all going into a 34' Ford pickup. Fully fenderless. Low. Thanks!
If you're running a 2.56 gear, there's only one way to go--and get ready for the anti-Saginaw onslaught to follow--a Saginaw four speed with either a 3.11:1 or 3.50:1 low gear. That way, you won't have to slip the clutch to get it moving, but will still be able to cruise at low rpm with the rear gear you've chosen. Say you ran a wide ratio (2.54:1 low) Muncie four speed. Even if you stepped up to 3.08:1 rear gears, 2.54x3.08=an overall gear ratio starting out in low of 7.8212. A Saginaw with a 3.11:1 low times your 2.56 rear gear=an overall starting out ratio of 7.9616. If you find a 3.50:1 low transmission, overall ratio in low goes up to 8.96. With a wide ratio Muncie, you'd have to move up to 3.55:1 rear gears to get a steeper overall ratio in low (9.088:1).
Muncie SM-420 truck granny box from a 55-66 chevy pickup the shifter will look old timey, added bonus!
I think I found a good candidate.... Tremec TKO 500 for GM's. GEARING: GM TKO-500 (TCET4616) 3.27 1.97 1.34 1.00 0.68 Should go nicely with a 2.56 posi rear according to my calculations. 3.27 should be a reasonably quick 1st... not to mention that the Pontiac 389 has no lack of raw torque.... and a .68 5th gives a great OD gear. (Or a high top speed.... hmmmm. )
FWIW, in my 52 Chevy, I have a 2.73 open rear with a wide ratio Muncie M-20 and 29" rear tires. It feels like I'm always starting off in 3rd gear. (But the fun part is that there are 3 more gears after that! ) 2500RPM in 4th (1:1) = 73mph. If you go with the TKO, you might find that you'll get better mpg by not using 5th gear! I actually get better mpg if I can keep it above 70mph (22.9 mpg on the way home from the Roundup!) than I do when I average 60mph! Basically, you wanna keep the RPMs at the bottom end of your engine's torque curve for optimal efficiency. I think some of the Super T-10's had deeper first gears than the Muncies. Summit sells new ST10's with a handful of different gear ratios to pick from.
Are you flying this thing or driving it? Holy Cow.....do the math. At 6000RPM at 1:1 in the trans and 30" diameter tires your over 200MPH! Add an overdrive trans into the mix and your into warp speed. If your going to run an OD box then install 3.50:1 gears and enjoy reasonable RPMs at cruising/highway speed AND enough gear reduction+torque to blow off the tires at will. I completely understand the need or desire to run whatever you have laying around but a well rounded/well thought out package thats correctly matched up will be oh, soooo much better, quicker and more reliable (easier on the clutch, etc) while still pulling down respectable mileage numbers. -Bigchief.
6000 RPM's wouldn't be very good considering that cl***ic Pontiacs like to destory themselves around 4500rpm's if you hold them to it too long. The rear end I have is the rear end I have. It's the same rearend that was run in cop cars, and with good torque (which the poncho has more than enough of) and a decent ****** there's no reason it won't be just as good. In fact, low bottom gears and high top gears would give me the best of both worlds, would it not? Either way, I'm also looking at a posi setup that will fit my housing that's a 3.08. I don't personally want to go up to a 3.55. As for flying or driving, I hope to do both. I want it to be a cruiser. As I said, I'm not into drag racing. I'm quite excited about sometime getting the car out to B-Ville and seeing what it can do.... which is when that high gearing on the top end would come in extremely handy.
Not enough gears. I like shifting, and I prefer at least 5 gears myself. Hell, if I had it my way I'd drop a richmond in there with a high 5th conversion. Too bad I can't find a god damn high 5.
6000 RPM's wouldn't be very good considering that cl***ic Pontiacs like to destory themselves around 4500rpm's if you hold them to it too long come with me to the wayback machine and Mr. Peabody will send us back to 1978 .... then we'll go for a little spin in my 69 GTO Judge... saw 6 grand on a regular basis.
I've done this very same thing with a few variables...my car was a 3300 lb 50 chevy sedan delivery and the final ratio was 2.29 to 1. The Heathen knows what he's talking about. Go find a cheap-*** vega 4 speed saginaw. Look for the one with 3 rings machined into the input shaft, where the clutch disc rides. The 3.50 [some guys argue it's a 3.40 1st gear...it ain't] first gear will allow you to come off the lights without having to slip your clutch much. The RPM drop through the gears sounds similar to a close-ratio muncie in a light car with good acceleration. Plus, you'll be able to kick anybody's *** in a reverse-gear race! When you settle into 4th gear, sit back and let the engine idle down the road at 75 mph. I wouldn't reccomend a big cam with this drivetrain setup. Uhhh.....is your '59, 389 my old one? Didja get it from Smalltown speed? If so...you're either gona relpace the lumpy cam or go for some steeper gears...maybe drive it around in 3rd gear? If it's a stock-cammed 389....grab your *** and hang on. The low RPM torque with those 2.56's will get you to about 150 MPH before the engine complains.. Do you own this engine? If so, it has a pretty radical ram-air IV cam. I did install Rhoades lifters to help get a little bottom end torque.Hell, it may be ok on a light model A, even with the killer cam...Photo of engine
That's the info I was expecting from someone with experience with my motor. To answer your query, nope, my 59' isn't your old one. Mine came from a local guy in Minneapolis who had purchased the complete 389 and a brand new still stickerd GM manual bellhousing/pressure plate/flywheel for a hotrod he was building when he was a kid. He started to work on the car and never finished it. Now some off 40 years later he and I were chatting and he offered to sell it to me. I picked up the entire setup for a song cause he knew I'd put it to good use. It's a stock cammed 389 and I've got a tripower to drop on top of it (***uming I can find carbs. haha). Everyone I've talked to who has personally owned one of these mills has said the same thing. TORQUE with a capital "T"! That's kinda the reason I bought it. Here's the basics of the equation I was thinking of... correct me if I'm wrong. 1 lightweight truck + 1 VERY Torquey motor + 1 low 1/2/3 gear and higher 4/5 gear ****** + 1 high geared rear end= A tiny hotrod that can come off the line rather quickly and respectfully, but can really lay it down on a long stretch for some serious speed. Like I said at the beginning of this post, I'm not really into drag racing. Hypothetical: I want a pickup that is geared to run well at bonneville, but still has the ability to get off the line and suprise a few people in the process. I think that the correct transmission would definitely let me achieve that goal. I've heard things about the durability of the Saginaw.... especially packed behind something like a 389. Any thoughts? Thanks for the reply. Most helpful!
a friend has had a saginaw 4 speed behind a warmed over 396 in his old pickup for a couple decades...he drives it sanely. You can break one if you want to, but if you're easy on it it'll live.
My '60 Pontiac the 389 was pretty happy with a 3.08 gear. I had 235/75R15's on the back most of the time, it would run around 1800 RPM at 65 and give me just about 20 MPG on the highway - with the stock hydro, and the stock 2bbl carb. I never ran it much over 4400 RPM, but you never needed to, moderate acceleration in that car would take you past everyday traffic like it was standing still. What are the ratios in a stock Hydramatic, for comparison's sake? I'd almost be afraid of one in a light little pickup, no matter what gear is in it you'll be able to buy tires on a weekly basis if you want to. Sounds like a lot of fun actually, hmmm..... Stock car guys run those Saginaws, I remember the tech article telling you to look for the three rings for the best gear ratios. I think I even have one somewhere I bought years ago. You want one out of a Monza that came with a 305 motor, as I recall.
Thanks for the responses guys! Good info here! From what I gather the Saginaw will either be a 2 groove (3.11 1st) or a 3 groove (3.55 1st). The ranging goes to a 4th gear of 1.00. If that gearing sounds optimal (which I thought it did) then I'll probably still invest the $$$ to buy the Tremec up above. It's got very comprable gearing 1-4 to a Saginaw, but it has the OD 5th gear. Thanks again for the replies. You guys rule.
If you're plunking it down for a Tremec, you might give the Richmond "4+1" a look just for comparison. The reason I'm saying this is b/c everyone I know that has put an OD ****** in front of a tall rear gear has been disappointed. The mileage really isn't better since you are barely above idle, and not really into the torque curve yet (especially if you have a warmer-than-stock cam and/or intake). The 4+1 ****** has a 1:1 5th gear, so it really acts more like a 4-speed plus a real low granny gear... pricing is slightly more than the Tremec, plus you'll hafta get a shifter to go with it. Just MHO, but I think you'd really be happier in the long run with a 1:1 final gear if you're gonna keep the rear gears that high. If you want OD, you'll end up changing out the rear to something at least 3.20's or numerically higher (if you don't sell the truck first). Check the Richmonds out @ Summit.
Already compared. I actually want the Tremec specifically because of the gearing... that really tall 5th won't barely get used at all. I'm not going with that tall 5th for fuel economy... I'm going with it for overall top speed that it can supply. Obviously, in terms of possible top speed runs, a 1.00 5th will be a significantly slower top than a .68 5th. There's nothing that says that you have to run it in the OD gear on the freeway. If I can spend less money, get a higher top end gear, and still cruise a 1.00 in 4th on the road with a decent economy, but still have that relatively low 1-3 gearing, that's really the best of all worlds. As for the rear end, I don't plan on changing it at all.
OK... that makes sense. It sounds like your expectations are a lot more reasonable than the usual installer of overdrives. Now go squeal some tires!
That's the part I'm really pumped for! Now if I can only find some good 30" profile cheaters for the rear....
IF you've got the horsepower. 4500 rpms with your setup in 4th would give a speed of almost 160 mph. I doubt a reletively stock 389 has the power to push your truck through the wind that fast, but if it did shifting to a tall .68 5th would drop the rpms down a lot and you'd find yourself slowing down, not speeding up. Just another thing to think about... -Bones
Reaching top speed isn't instantanious in high gears like it is in low gears.... that's why flats like bonny are well over a mile long. As for the motor not having the power, I disagree. A 59' Poncho 389 tri power will lay out 350hp and around 425tq all between 2800 and 3400 RPM's. It's not the lack of power that would stop a hot rod from hitting 160... it's a lack of aerodynamics. 160 isn't exactly unachievable in a hot rod you know....
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