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Ok, I know this has been discussed a million times and after reading the archives I think I know what I want to do but wanted to post and see what everyone thought.

I have a 55 2nd series 1/2 ton with a 235, 3 on tree and 3.90 rear gears. I also have this thing for things that go fast so...

I am thinking of keeping the 235 (its nice, its simple, and I have all the parts), putting in a 3.55 ring and pinion from Patricks and a T5 with .73 in 5th. From my calculations with 30" tires I show 82MPH at 2500 RPMs. Even with the stock 3.9 I show 74mph in 5th.

My understanding is that a 235 will tolerate 3000 rpms for a bit but not sustained without causing engine wear. Will it be happy at 2500rpm for several hours? I don't think I want to go any smaller on the rear gear as that will drop takeoff.

Any comments or suggestions welcome.
thanks

Your 235 will run for years at 2,500 rpm. One other item to think about is a brake upgrade if you're wanting to run that fast.

The 2500 RPM won't be a problem for your 235, but this combination of gears will net about 2.59 final drive ratio in OD 5th. You will be down shifting quite a bit. If you could actually pull 82 mph with a stock 235, I'd be REAL surprised. Scared too, with stock brakes & suspension! A 3.73 or 3.90 rear would be my choice here, and give better acceleration around town.

The factory geared the '55 trucks with 1st gear about 3:1, optimum with the 3.90 rear. You'll lose some punch by going to 3.55. With the OD 5th, you really don't need that much reduction. Of course a 4.03 1st gear S10 T5 will restore the initial gearing, but that's a real wide ratio tranny and it's entirely possible the shift to 5th gear would cause the motor to just go flat, i.e, drop RPM but gain no speed. Even if not, I still think 2.59 is too tall for a stock 235 to pull comfortably.

Ok, I should have told you I will be going with disc brakes on the front. Still undecided as to disc/drum on the rear.

sixpack, thanks for the info...something to think about. I really don't want to lose good acceleration around town but wanted to be able to cruise on the highway. I will go back an review the numbers with 3.9 rear. If I remember correct it still had very decent speed, 74 @ 2500 rpms and if necessary I believe high 80s at 3000 for a bit of acceleration.

Welcome to the 'bolt, ChevyGirl. I agree with the above comments; swap the tranny first and see if it needs the rear gears changed, I'd bet it doesn't. 3.55 is not a huge jump from 3.90, it may do more harm (1st) than good (5th). It will definately need brake and suspension work to safely pull it back down from 75+ mph.

Are we going to see this truck in the gallery?

Thanks for the welcome.

What suspension work would you all recommend. I wasn't planning on anything major in that area.

As for the gallery, maybe in a few years. Right now it is in pieces in the garage. Am doing some tinkering while waiting for it to warm up enough to por 15 the frame and don't want to rebuild old tranny before deciding if I was going to keep it. It needs major body work but at that age who/what doesn't

I'll keep you all posted on decisions.

Agree with Hedgehog and the others... I don't think the 235 will be able to overcome the wind resistance at high speed in overdrive.

Remember you are basically pushing a shoebox through the air, and the wind resistance goes up dramatically. If you had a streamlined vehicle and a high-torque engine, it might work.

I'd leave the 3:90 in place and see how it drove with the OD transmission.

Once had a company truck, a base '82 Chevy S-10 with an Isuzu 4 cylinder. It ran fine unloaded, but if anything loaded in the bed was higher than the cab, it would actually run about three MPH higher in third gear than it would in high (fourth), due to wind resistance.

---> Bill

From what I am hearing it sounds like I might need to get a bigger engine.

What do you all think would be a realistic crusing speed to expect?

thanks for all the info

keep that inline!
I vote for swap the trans, leave the 3.9 and upgrade your 235 with dual headers, dual carbs and new dist. I bet you will be happy with that but if not you can always do more to the motor like a cam and head work.

Where do you plan on driving this rocket ship ?

If you're keeping the straightaxle front end, a popular package seems to be monoleaf springs, short HD shocks, sway bar(s), front disc brakes (you'll need a new master cylinder). It addresses most of the big issues and passes for stock to the casual observer. Keeping rear drums means you won't have to re-invent the parking brake; they work fine if maintained properly.

In my mind there's a line you cross when you go IFS. At that point you might as well shove a 350/350 package in it and chop the top. :rolleyes:

I have a rice rocket to go fast. My truck is for trucking.

For suspension upgrade I suggest going to Patricks and getting his mono leaf front and brand new lowering blocks for the rear. Much safer to have the truck a little lower.

Keep it around sixty five and stay alive.

Thanks for the suspension info Hedgehog, I'll be looking that stuff up tonight. And thanks to everyone else for all the great thoughts and ideas. I am planning on dual exhaust and maybe in the future dual carbs

I would really like to keep the inline. Can someone with a similar setup tell me what crusing speed I should expect. with the 235, 3.9 rear and T5 overdrive?

I am not looking to cruise around at 80 all the time but I want it to be there if/when I need it. I don't think 65/70 is unreasonable.

So guys and gals, what can I expect???

thanks

A lot of wrenching, a few cuss words(maybe) , A good supply of money and a few good friends to persistently help through the upgrades
I would not be concearned about rear disc-brakes as the front brakes do most of the stopping anyway.
A cam out of a corvette 235, talk to Tony about his in-line 6 distributor upgrade(not pretty but works), maybe dual carb & manifold and a split exhaust from Kansas Kustoms http://www.inliners.org/Advertisers/kkk_ad1.html

My '51 truck, 3.90 rear, with .70 overdrive and 28" tires, is turning exactly 2200 RPM at a verified 70 MPH. So with the taller tires, you'll be turning a bit less RPM at the same speed. Nice comfort range, good passing torque, well below the governor - driver wimps out at anything over 80, slows down to let tailgating Acuras & BMWs pass - they just can't stand being behind an old truck going this fast.

I run the T-5 with 3.90 rear and 235 and like the gears as they are. I do live in Ct. and there are a few hills. Also towing a pop-up I would not want to go with a 3.55 rear. I run about 65 @ 2100 RPM, a good cruise IMO. Jack, I have had it up to 80 or so with this set-up, it's possible, and yes it is a little scarry.

You guys are awesome! Thanks for the great info and yes, I will be keeping the 235.

I will be off in search of a T5 this weekend. From what I have read on the tech pages I should aim for a 85 s-10 or an 85 astro with a mechanical speedo. Any other hints would be great.

Look at Inliners T5 page for some useful data on selecting the correct T5.

If you can find a dual point distributor kit that works almost as well as an HEI but is cheaper. I bought an upgrade plate off of ebay about six months ago (for $10, no less) that had everything but the points. I just installed it in my spare distributor and it went in really easy and looks spiffy, I'll have to take a picture of it. It looks like it is factory, and has a special bracket on the outside of the distributor for the condenser. Dual points increase the dwell of the coil to give you a hotter spark and double the point life because one set opens the circuit and one set closes it.

If you want to keep it inline and get a bit more power, you could find a 261. It's a big bore 235 with heavy duty rods, more agressive cam, and full flow oiling, with better cooling passages. They are found in two ton trucks and busses, and canadian pontiac cars. They are a direct bolt in replacement for the 235 and have more HP and torque.