The Stovebolt Site Forums The Shop Area The HiPo Shop engine swap questions

first off, the truck is a 59 1-ton with a 235 and four speed manual with the granny gear.

i found a cheap 350 to swap in for my 235. it comes with a th350 tranny. here are my questions:
-will the 4 speed tranny that is in the truck now bolt up to the 350?
-will the 4-speed explode behind the 350 (will have 200 hp when i put it in, but will change the heads/cam to get it to 300-350 hp)
-if i use the th350, will the original driveshaft work? will it be long enough/mate up to the th350?

The trans. will fit useing a 63-72 bell housing.
It will not last long with that kind of power
& the ratios are wide. It would not be a real
good driver. You might use a 4Speed car type trans.
or a 5-speed from a late model chev. truck.
Any drive shaft shop can modify the drive shaft.
What about the E-brake. Is it on the back of
the trans.?

It will with the right bellhousing.

Maybe

change the above maybe to probably

No, you'll need one custom built.

Side note: If you want a race truck why are you starting with a 1-ton?

Question: Do you know that your rear end ratio is lower than 5 to 1?

because i bought it for $1.00, and it will not be a race truck, it will more like a mild street rod.

the rear end will be replaced eventually by a 12-bolt, or 9". what is the rear gear ratio for a 59 1-ton? does anybody know?

get a six speed from a 94 up camaro/firebird.its double overdrive will tame that rearend.

Zenish that's interesting on the 94 camaro--I am unfamiliar with that--do you know the ratios on that tranny?

Try this site

Or do a Google search for T56 transmission. Lotsa stuff out there on them.

There are better ratio differentials from later trucks that can be swapped into that axle. Some even came with factory Detroit Locker units. The old Eaton drop-out axle ended production in '72, look for '67-'72 trucks for the best ratios.

Yeah compare the price of a 94 camaro 6 speed. You may think twice about using when after you price them. I had to have my 6 speed rebuilt in my 97 camaro ss. The previous owner cooked it. A junkyard unit was 800-1400 bucks. Rebuilt with warranty was 1800.00. Ouch. It is however a nice transmission and the car really flies.

Also on the truck I put a 283/th350 combo in my 54 and used chevy duty mounts with great luck. You can see pics on my website.

both fifth and sixth are overdrive with sixth .50 over.

Two overdrive gears?

Since you are going to have power loss every time you use a pair of gears or a planatary set, wouldn't it make more sense to have the highest gear (sixth in this case) be direct, and then determine the correct rear gear ratio, and then the rest of the gears in the transmission?

I guess I need an engineer to tell me this design is driven by something other than marketing.

The reason the drive ratio is changed in the transmission and not just the rear end is all for packaging. The T56 trans commonly has 2.97:1 first gear ratio, (though there are 3 or 4 others available depending on application), with a 3.42:1 rear end gear, you get 10.15:1 final drive,

If the 6th gear were 1:1, then the rear gear would have to be 1.71:1, which to achieve the same first gear final drive would require a 5.94:1 first gear. Basically you would need a larger transmission case to house the gears, which would then take up more interior space, or eliminate any ground clearance.

There would also be an issue with a 1.71:1 rear end gear, you would either need to use a VERY large pinion gear (not a good idea), or a small ring gear (would limit power handling capability).

As a side note, If I could afford a T56, I would put some 4:56 gears in my truck to take advantage of it. (I don't see much point in having your cruise speed be at 1200RPM)

Thanks 3100 for explaining that. I guess since all my toys are trucks, ground clearence hasn't been something I've though about too much...

And welcome to the Stovebolt! Did you join just to answer my question?

OldSub -

I just happened to find this website a few days ago - thought I might as well join

I'm glad you did. Fun bunch here.

I'm new to the early chevy trucks but I think that 4 speed you have is a sm420??? correct guys? If that the case then it is a very strong tranny. Much stronger and more reliable than your th350. I went thru a th350 a year in my wheeling truck...but since I switched to a sm465 (the newer/weeker version of the sm420) I have yet to hurt it. Its also stronger than any of the car trannys out there....

But there are drawbacks. First gear (granny) is a 7:1 and isn't sincroed. There is a big gap between 2nd and 3rd. Plus its a truck tranny so its going to have to be shifted slow compaired to a car tranny. I would also upgrade to a bigger clutch. The 2 420's I have sitting here have clutches much smaller than the one I use in my wheeling truck.

thanks for the response. is there any way i can find out what it is using a casting bumber or something? any idead where to look on it? what are the drawbacks of the gears not being syncroed? any ideas on a larger clutch that fits?

Old Sub, I might try to answer your question about two overdrive gears. Your idea to use the final overdrive gear as a 1:1 and then adjust the rear end ratio is typically the European approach. It is also the way Richmond approaches the issue on their 5 speed. Their 6 speed, however, does overdrive 6th gear.

Back to your question, double overdrive isn't really a marketting ploy. That is how the new Corvette gets almost 30 mpg and accelerates like a big block. That double overdrive makes the engine just loaf at highway speeds.

I guess it's all in how you look at it. If you're going to change the differential anyway to get a posi, or a more highway-friendly rear end ratio, then it would make sense to go the Richmond route, and have 1:1 fifth be your overdrive and take advantage of the much steeper first (compared to a Muncie for example). That could end up being the route I take.
But if you're happy with the rear end you've got, then getting overdrives would make sense to get the rpm's a little less buzzy on the highway.

A thought comes to mind. The strong 420 transmission described above, with it's wide gear separation, would do really well if you could get a Gear Vendors overdrive unit on it. It would turn the 4 speed into an 8 speed with the 0.78 OD. Try that with a close ratio Muncie and every overdriven gear is equal to the next gear anyway. But on the 420, it might actually give you 8 real gears to choose from. Hmmmm.

The only problem with the SM420 is the "granny" first - the only thing it's really good for is starting with a heavy load or climbing over rocks. Doesn't the owner's manual even recommend starting in second when unloaded?

I don't know. But I have an uphill driveway and a lot of times I'll get into first to creep over the curb and up in my driveway. I've also used it on especially steep streets when taking off. I'm sure I'll use it when I tow things too.

I'm glad it's there, even though I don't use it too often. I almost always start off in second gear from a light in normal driving.

Nobody answered the question about the axle ratio! But with those stock gears, you'll top out at 55, and that may be a liberal estimate. Were it mine, I'd stick a T-5 in it and be done. Good luck with it, 1-ton of fun!

WITH A 1TO1 FINAL RATIO IN A ONE TON THAT IS NOT GOING TO BE USED AS WORK TRUCK THE REAR AXLE RATIO CAN BE CHOSEN FROM A WIDE RANGE.IF YOUR TRUCK DOSEN'T DO MUCH HI-WAY 3.70 WILL WORK FINE A COMBINATION RATIO 3.54 TO 3.25.FOR ON THE HI-WAY MOST OF THE TIME 3.00 TO 2.73 WILL WORK.MY OLD 51 MERC TRUCK RAN HI-WAY WITH A 390 AND A BORG WARNER T18 WITH REASONABLE MILAGE WHEN I KEPT MY FOOT OUT OF IT.THE REAR RATIO WAS 2.75.GRANNY GEAR 1ST WORKED WELL TO CRUISE SLOW BUT THE TRUCK WAS A SLUG UNTIL 30 MPH THEN LOOK OUT.SO NOW MY 52CHEV TRUCK IS A 235 WITH A TREMAC 4 SPEED 4TH IS .78 3RD IS 1TO1 WORKS FINE WITH 3.54 REAR AXLE RATIO.SO YOU DECIDE WHAT YOU WANT AND GO FOR IT. AS I SAID TO THE WIFE "THERE IS A TRUCK UNDER ALL THAT RUST TRUST ME" R

try switching cap lock off
that realy gets some people fired up because thay think youre yelling at them

The factory gear ratio on that 1-ton will probably be over 5.00:1.

SORRY FOR THE CAP LOCK MY SON BROKE THE KEY.NOT RAISING MY VOICE JUST TRING TO RAISE A STUCK KEY.

THAT'S A 1TO1 AT THE TRANS NOT AT WHEELS

I've got 4.56 gears in my 3/4 ton and I can comfortably drive at 65, which is about 3000 rpm. I can go faster, I've gone up to 75, even 80, which is around 3500 rpm, but the vibrations from the driveline are so bad that I tend only to use that speed for passing in the left lane.

If I switch to a 3.73 rear end, (if I buy my friend's posi Dana 60), my top speed would probably be almost 90, but unless I fix my driveline vibe, I probably still won't be able to exceed 65!

A 1959 Chevrolet 3800 had a 5.14:1 rear axle ratio.
Ref.: 1959 Chevrolet truck specifications in the "Resto-pac".

for you folks that are interested in that t-56

Here is a link to a place in Oregon that will custom build one to your needs based on rear end ratio and application.

http://www.sallee-chevrolet.com/BorgWarner/bwt56.html

I called these guys about this tranny and spoke with them for quite a while - very friendly, helpful and informative.

- Ryan

WO, keyboards are cheap these days. Watch the office stores' ads, sometimes you can get a $10 keyboard on a "free after rebate" deal.

Sorry about the off-topic post.