55 3200 drivetrain questions

[Msanantonio]

I have a 55 second series3200 (longbed) with a 350 chevy crate engine Edelbrock upgrades, a saginaw 4spd and the original HO33 rearend. Based on the serial # the truck originally came with the small v8 and the 4spd and what I beleive to be 4.10 gears. We spent the better part of the spring getting it back on the road and have been having a blast driving it this summer. Need some advice on the tranny and rear gears. I drive it a lot and sometimes travel at highways speeds engine is at 3300 rpm at around 65 mph. There are some drivetrain issues that I want to address in the fall. there are a lot of pros and cons to the saginaw (hp limitations ,durability gearing vs. availability and low cost to fix) does anyone have any thoughts on a good transmission /gear combo?

At the very least I am planning to open up both and refresh them as necessary as the tranny has a noise in 4th gear a rattle not loud and not at a high frequency. There is a also vibration (shudder) around 22-2300 rpm that goes away it's not gear related. This has the original 2 shafts with the center bearing.
Pinion angles look ok and clutch is not slipping.

Would like to keep the original rearend thinking the cheapest fix is to put a set of lower gears. I think the options back then were 3.38,3.90 and 4.10. I am not in favor of the 3.38 but it may be the easiest way to drop the rpm sat highway
speed.

The other options? I'm thinking is a 5spd . Not looking to break the bank at least for now. Thanks for your feedback.

[Hampshire]

3:73 seem to be a real popular option here. I have one out of a Nova in my 49 AD

[OrrieG]

3.73 is the ratio most 70's chevy trucks run with TH350 trans with 1:1 high gear output. I think some of the 4 speed (granny truck) got 4.10. Your stock ratio was made for a time when most truck putted around town or the farm and a trip to town was on a two lane road at 45 mph. For a while I had a 1 ton rear with 4.56 gears behind my 4 speed 235, but most driving was in town or on curvy mountain roads, when I put in the 3.73 I was amazed at how much faster I could get places I liked to hunt and fish. If you are going to spend a lot of time on the freeway 3.54 might me better if you can find one. You will probably find you can get a whole newer rearend for less than new gears for the stock one. There was a recent thread with links to rpm/trans/ rearend/tire dia calculators if you want to mess with them.

[Msanantonio]

Thanks for the info. Yep the history of these trucks are great.
I like the idea of the 3.73 or 3.55 just not sure you can get gears for the HO33 If anyone knows of a company that does please let me know thanks. Also what other manual transmissions fit behind and 350 . I know the position of the shifter can be a challenge.

[1project2many]

3.90 and 4.10 gears are very close. Most people don't notice the difference. 3.38 gears are a great ratio for a low rpm cruiser but you'd better be sure the engine's built for it. Reducing rpm significantly below the torque peak has a bad effect on fuel economy. Ask GM when they first started moving to numerically lower gear ratios to try and reduce tailpipe emissions.

Are you using a truck or car transmission? If it's a car trans there are a few different 5 speeds that can replace it fairly easily. The T5 is a common swap although it's not a really strong trans. The NVG3500 is also usable. If you have If you've got the $$ a T56 would be a nice trans to run with the 4.10 gear as it's a dual overdrive unit with 6th gear ratios at .62 or .50:1 depending on the gearset. And if you like truck transmissions, the NVG4500 retains the original creeper gear used with the Muncie 4 speed truck trans while adding OD. The shifter is farther back so some modification will be required.

[roger55]

Originally Posted by 1project2many

... Reducing rpm significantly below the torque peak has a bad effect on fuel economy.

I totally disagree with that statement.

[1project2many]

Originally Posted by roger55

I totally disagree with that statement.

Hmmm??? Oh, I see.

As a statement by itself it's worthy of discussion. Taken in context with the complete answer I think I can demonstrate validity. With no knowledge of engine specifics other than being told it has some changes from the original, unknown configuration, it would be very unfair to the OP to say that reducing RPM by 20% will increase economy when there's a high probability that cam overlap, poor atomization, poor scavenging, wrong head design, and / or improper spark and fuel curves, working together or individually, will impede success. Matching peak torque rpm and cruise rpm is a great rule for people who enjoy building more than they enjoy the design process and produces positive results more often than not, especially with mismatched engine components.

So this was how it "read" to me as I was writing it: "3.38 gears are a great ratio for a low rpm cruiser but you'd better be sure the engine's built for it. Reducing rpm significantly below the torque peak [when the engine's not built for it] has a bad effect on fuel economy."

[Katrina/10]

As far as I know, there are no other ratios available for the HO33 other than original 3.90, 4.10, or aftermarket 3.38. I wanted to keep the original axles in my 51 and 55, but get a little more highway speed out of them. So I installed the 3.38 in both, and it works great. Its not like having overdrive, but much improved over the original ratio for highway driving. Still fine around town, and even some light towing. Neither truck has overdrive.

If you want to keep your original rear axle, that's what I would do.

[roger55]

Originally Posted by 1project2many

...Reducing rpm significantly below the torque peak [when the engine's not built for it] has a bad effect on fuel economy."

A cruise rpm for maximum fuel economy will always be significantly below the torque peak.

If you had said "Reducing rpm significantly below the torque curve drop-off has a bad effect on fuel economy", that would be accurate.

[Msanantonio]

Thanks for the input and discussion. The truck is what I would call a daily driver during the summer and into the fall. Looking for setup that lets me drive to shows and cruise-ins and is reliable (truth be told the gear set up fun and surprises people when to let is rip). The saginaw may not be the best choice but it's what I have and the the final ratio is 1 to 1 . Right now everything fits and it's simple. So I'm think ing the cheapest solution is the rebuild of the tranny over the winter and gears in the original carrier will be the way to go. While I'm at it going to do the clutch and check the flywheel...as I have a vibration that I can't pin down. Some other 55 owners in NY have 3.55 gears (not the original rear-end) and tell me that it's a real nice set up so the 3.38 is not too far away from the 3.55 and is available for this carrier. I have other projects on the truck I also want to tackle like disc brakes up front....either way I'm waiting to the fall and meantime I can keep getting more information from fellow second series truck owners. Thanks

[57taskforce]

I'll stir the pot. While I see both sides of the argument above, I'll add this, I tend to side more on an engine built for a little lower rpm performance in a non overdrive, numerically low rear gear choice. At the very least the cam could be degreed to allow peak torque at a lower (or higher) rpm.(most of us vortec 454 guys know a lot about factory bad cam degree.) While cam degree won't change overall output of torque it will change when peak occurs. Peak Torque at a lower rpm will make it more drivable under normal conditions(ie. 3.38 gears crising on the highway, not having to constantly search between transmission gears), at a higher rpm will obviously allow a little more high rpm passing power. I feel that to maximize your performance and efficiency, you need to have the engine built to suit the rpm levels it will be functioning in. These are some things I've learned and experimented with in both the 350 in my '57 and the 454 in my '98.
To the op: if it were me, I'd keep the 4:10s and swap an overdrive trans in. Though it does take modification to install, the nv4500 won't fail you.

[roger55]

Originally Posted by 57taskforce

I'll stir the pot. While I see both sides of the argument above, I'll add this, I tend to side more on an engine built for a little lower rpm performance in a non overdrive, numerically low rear gear choice. At the very least the cam could be degreed to allow peak torque at a lower (or higher) rpm.(most of us vortec 454 guys know a lot about factory bad cam degree.) While cam degree won't change overall output of torque it will change when peak occurs. Peak Torque at a lower rpm will make it more drivable under normal conditions(ie. 3.38 gears crising on the highway, not having to constantly search between transmission gears), at a higher rpm will obviously allow a little more high rpm passing power. I feel that to maximize your performance and efficiency, you need to have the engine built to suit the rpm levels it will be functioning in. These are some things I've learned and experimented with in both the 350 in my '57 and the 454 in my '98.
To the op: if it were me, I'd keep the 4:10s and swap an overdrive trans in. Though it does take modification to install, the nv4500 won't fail you.

No disagreement here. Moving the peak torque lower is also going to most likely shift the whole curve lower.

Here's a dyno chart from an LS1 (flywheel measured):

http://www.hotrodders.com/gallery/data/3537/LS1.jpg

Notice the peak torque is about 4,000 rpm. Yet, the cars they put them in had a final ratio of about 1.70 (T56 with .50 6th gear combined with a 3.42 axle ratio). They would get extremely good gas mileage running on the highway at about 1,600 rpm at 70 mph. That's an engine speed that is 60% less than the peak torque. Also notice that at 1,600 rpm the torque is still a little over 300 ft-lbs because of the extremely flat torque curve of these engines.

In an older designed engine without fuel injection or a roller cam, you won't see these kinds of numbers. Normal built 400's, 383's and 350's without radical type cams all have decent torque curves. The shorter stroke 283's, 302's and 327's are not as good. We are also talking about vehicles that have no where near those newer car's aerodynamics.

Based on what the OP has said about his 350, I'm going to say he doesn't have an overly aggressive cam and that a good rpm to shoot for for highway cruising would probably be around 2,200 to 2,300 at 65 mph just like he said.

If he does run 3,300 rpm with 4.10 gears then his loaded rear tire radius is 13 1/2" (that would be around a 28" diameter tire). Changing to a 3.38 ratio will give him 2,700 rpm at 65. Still higher than ideal but a significant improvement in noise and mileage. This is surely not going to be too low of an rpm at all.

The only thing I don't like about going to a 3.38 is the investment value. Not a lot of parts are available for these rears and a posi is not available. Parts that are available are on the expensive side and gears are imported. A rear swap makes more sense as far as an investment IMHO.

See this:
http://www.tomsdifferentials.com/201...og/Pages13.pdf

[roger55]

Originally Posted by 57taskforce

...
To the op: if it were me, I'd keep the 4:10s and swap an overdrive trans in. Though it does take modification to install, the nv4500 won't fail you.

Good advice but the 700R4 is the most economical and easiest way to get the objective he's asked about.

Keeping the 4.10 and going to the 700R4 will give a final ratio of 2.87 (.70 OD X 4.10). That will yield him a 2,300 rpm at 65 mph. It will also improve the off-the-line performance with the 3.06 first the 700R4 has. Biggest draw back would be no posi and that would be pretty huge. He would really, really want one with that setup because without that and the light rear of a pickup, you'd have to be very careful or you will be spinning that tire easily. There is the other side of that though. If you break them loose with a posi, you've got to be careful of the rear of the truck coming around on you. A concern in wet weather and a bigger concern if the OP lets anyone drive his pickup without experience in that regard.

If it were me, I'd do both. Get a 700R4 and swap the rear end out to one with a posi.

[57taskforce]

Originally Posted by roger55

Good advice but the 700R4 is the most economical and easiest way to get the objective he's asked about.

Keeping the 4.10 and going to the 700R4 will give a final ratio of 2.87 (.70 OD X 4.10). That will yield him a 2,300 rpm at 65 mph. It will also improve the off-the-line performance with the 3.06 first the 700R4 has. Biggest draw back would be no posi and that would be pretty huge. He would really, really want one with that setup because without that and the light rear of a pickup, you'd have to be very careful or you will be spinning that tire easily. There is the other side of that though. If you break them loose with a posi, you've got to be careful of the rear of the truck coming around on you. A concern in wet weather and a bigger concern if the OP lets anyone drive his pickup without experience in that regard.

If it were me, I'd do both. Get a 700R4 and swap the rear end out to one with a posi.

Sorry I should have been more specific: I was assuming he wanted to keep the truck a manual. If he's willing to swap to an auto than certainly a 700r is the way to go. I got the impression for some reason he wanted to keep it a stick.

[Msanantonio]

great discussion . Want to keep the manual and it sounds like the 3.38 maybe the answer for now. I can always change the whole rear-end down the road. Still going to hold off for a while. Having way too much fun just driving it....

Quick change of subject several fellow 55-58 owners have been telling me the for the front disc brake swap the power booster is really not necessary? Thoughts? I know the kit is complete but just thinking about space with the exhaust running close by and I haven't really given it a close look to make sure it fits (still on the frame under the cab)

[Msanantonio]

Another pic

[57taskforce]

Nice looking truck!
You Might want to check ogres brake setup out, it's in his build thread. if my truck was still on the stock frame that's exactly what I would do.

[roger55]

Originally Posted by Msanantonio

great discussion . Want to keep the manual and it sounds like the 3.38 maybe the answer for now. I can always change the whole rear-end down the road. Still going to hold off for a while. Having way too much fun just driving it....
Quick change of subject several fellow 55-58 owners have been telling me the for the front disc brake swap the power booster is really not necessary? Thoughts? I know the kit is complete but just thinking about space with the exhaust running close by and I haven't really given it a close look to make sure it fits (still on the frame under the cab)

I thought that might be the case as far as you wanting to keep the manual. Realize it is going to cost you about $700 to put that 3.38 in that rear. ($454 in parts and $50 for shipping plus about $150 - $200 for someone to put it together for you.) And, that assumes the rear doesn't need anything else.

Even with a rear end swap, you can't get your desired cruise rpm without a transmission change. If you went to a rear gear to get you the ratio you would need with your present transmission, your off-the-line performance would not be fun at all. Between the cost and/or more work involved going to an OD transmission, the 700R4 makes a bunch of sense.

I do understand that a lot of people just got to have a manual though. But, you might want to think about that pretty hard.

Btw in my '57 pickup, I put a 305 TPI in with a 700R4. My rear came out of a '65 GMC pickup (Dana 44) and it has a 3.54 posi. That's going to give me about 2,000 rpm at 65 mph. The 305 TPI has good torque at lower rpms and I expect it to be really good. I haven't had it out on the road yet as I'm not that far along in the project. Probably a few more months.

I also put a front disc kit from CPP on the truck and stayed with 6 lugs. I used their firewall mounted power booster setup that comes with a new swing pedal and bracket assembly.

[Msanantonio]

Thanks for the advice and the true cost... Which is something a lot of people don't think about. I would do my own work as I am capable but you do raise valid points. Probably will get to think about it for a while . I live in New York and plan on going to some of the fall shows including the adirondack Nationals at lake George ny the weekend after Labor Day ad there is usually a bunch of vendor and 55 owners to talk to....

[roger55]

Originally Posted by Msanantonio

Thanks for the advice and the true cost... Which is something a lot of people don't think about. I would do my own work as I am capable but you do raise valid points. Probably will get to think about it for a while . I live in New York and plan on going to some of the fall shows including the adirondack Nationals at lake George ny the weekend after Labor Day ad there is usually a bunch of vendor and 55 owners to talk to....

Kudo's to you for having the tools and experience to set up rear end gears. Not too many of us can do that. I do just about everything myself but setting up rear gears and upholstery. I've done a little upholstery but hate it so I'll never do it again.

When I bought my 3200, the PO had already swapped the GMC rear with 3.54 gears in but it was a sloppy job. I took it out and had to re-do the spring perches. It had the gears I wanted but I took the assembly to my rear end guy to check it all out. Everything was bad except for the axles. The gears were pitted badly so I had to buy another set of 3.54's. The spiders were shot too so I upgraded to the trac-loc as it wasn't much more money than the spiders anyway. I ended up with over a a thousand in it. My guy charged me $150 to set up the gears.

[1project2many]

Msanantonio, that's a nice looking truck.

I know there are disc brake kits out there but some of them don't seem to be well thought out imo. Most people don't think about how the truck will react if the brake bias is changed. Pickups in general and TF trucks especially have more weight on the front axle. Even with stock brakes the tail end likes to come around during aggressive or panic stops. Any change to the brakes that puts more brake bias on the front will make this tendency worse.

As far as the booster, I've been driving my 3200 with manual brakes since I put it on the road it up back in '92. For many years it was my daily and "I didn't need no stinkin' booster." But as I get older and drive the truck less often I find myself thinking about pedal effort. In heavy stop and go traffic my knee gets sore and my calves get tired. I'm putting in power assist. I've managed to find an original style Hydrovac and I plan to duplicate a factory booster installation. YMMV.

[1project2many]

From above:

Any change to the brakes that puts more brake bias on the front will make this tendency worse.

Should read "Any change to the brakes that puts more brake bias on the rear will make this tendency worse."

Humblest apologies.