[JimC0217]

Hey all, new to the forum and new to the Nova, just need some input if anyone can help. '74 350, 30 over, big cam, 373 gearing and I believe the original 350 trans. I was told when I bought the car the gears were swapped from a 4.10 to a 3.73 ratio so it will ride easy at highway speeds, because of the engine work. Finally got the car on the road, has trouble going in to gear at times but shifts fine, but the RPMs seem wound pretty tight just at 50 mph. Could this be a mechanical issue or is the trans/gearing ratio just all wrong? Thanks for any help!

 

[msaul]

Manually and visually determine which gear the linkage is allowing the transmission to be in.
Install a tachometer.
Manually and visually determine the rear axle ratio: count the number of teeth on the ring gear and divide by the number of teeth on the pinion gear.

 

[JimC0217]

Manually and visually determine which gear the linkage is allowing the transmission to be in.
Install a tachometer.
Manually and visually determine the rear axle ratio: count the number of teeth on the ring gear and divide by the number of teeth on the pinion gear.

Thank you for the reply, but I'm not sure what that will help?

 

[ramportin1]

Thank you for the reply, but I'm not sure what that will help?

Counting the teeth as he said will tell you if infact its 3.73 or 4.10 or something else

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[JimC0217]

Counting the teeth as he said will tell you if infact its 3.73 or 4.10 or something else

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If it is 4.10, or 3.73, will dropping to a lower ratio ease down on my RPMs?

 

[ramportin1]

If it is 4.10, or 3.73, will dropping to a lower ratio ease down on my RPMs?

Definitely yes. The higher the number the shorter the gears are so higher rpm in final gear for cruising at highway speeds

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[JimC0217]

Definitely yes. The higher the number the shorter the gears are so higher rpm in final gear for cruising at highway speeds

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Thank you. Would I be wrong to say a lower ratio would affect acceleration? Is there a ratio for a comfortable median or is there no way around that unless I change the transmission? I'd like to keep the original 3 speed and have a little jump to it when I punch it, but I also need to be able to hit around 60-70 without screaming. Hoping for too much?

 

[ramportin1]

Thank you. Would I be wrong to say a lower ratio would affect acceleration? Is there a ratio for a comfortable median or is there no way around that unless I change the transmission? I'd like to keep the original 3 speed and have a little jump to it when I punch it, but I also need to be able to hit around 60-70 without screaming. Hoping for too much?

Your thinking is correct in acceleration being affected and sure there is a good number to get a good balance of both ends, that magic number I couldn't give you for the 3 speed even if I knew every mod you had done, but hopefully a expert will chime in and help ya figure it out. Good luck man

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[JimC0217]

Your thinking is correct in acceleration being affected and sure there is a good number to get a good balance of both ends, that magic number I couldn't give you for the 3 speed even if I knew every mod you had done, but hopefully a expert will chime in and help ya figure it out. Good luck man

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Thanks for your help!

 

[RifRaf]

'74 Nova, 350, 30 over, big cam.

Is there a ratio for a comfortable median or is there no way around that unless I change the transmission?

A comfortable median for your set-up might be a 3.42 ... or a 3.55 differential ratio, but your engine will still be turning aprox 3000 rpm to cruise at 65 mph. A 3.08 differential ratio would bring your rpms @ 65mph down to about 2600 rpm.

BUT....You mentioned that your 350 has a "big" cam. Since you are also running an automatic trans, I'm guessing you have a high stall torque converter. Based on some of my prior drive train set-ups I had in my 74 Nova > big cam + high stall converter + 3.08 gears was a dog out of the hole (a lot of stall with little forward movement).

If you want to retain your engine's performance characteristics AND gain low rpm highway cruising, an overdrive transmission (with a lock-up converter) is probably the way to go. I run a very healthy 400 sbc, 4.10 ratio, and have a 2004R trans > 70 mph @ 2450 rpm... swapping to an overdrive trans was one of the best upgrades I made.
If you don't want to go the overdrive trans route and only address the differential ratio to lower your highway rpms, you may want to consider swapping your current "big" cam to a milder version... along with a matching torque converter.

 

[JimC0217]

A comfortable median for your set-up might be a 3.42 ... or a 3.55 differential ratio, but your engine will still be turning aprox 3000 rpm to cruise at 65 mph. A 3.08 differential ratio would bring your rpms @ 65mph down to about 2600 rpm.

BUT....You mentioned that your 350 has a "big" cam. Since you are also running an automatic trans, I'm guessing you have a high stall torque converter. Based on some of my prior drive train set-ups I had in my 74 Nova > big cam + high stall converter + 3.08 gears was a dog out of the hole (a lot of stall with little forward movement).

If you want to retain your engine's performance characteristics AND gain low rpm highway cruising, an overdrive transmission (with a lock-up converter) is probably the way to go (I run a very healthy 400 sbc, 4.10 ratio, and have a 2004R trans > 70 mph @ 2450 rpm).
If you don't want to go the overdrive trans route and only address the differential ratio to lower your highway rpms, you may want to consider swapping your current "big" cam to a milder version... along with a matching torque converter.

This is exactly what I was looking for. Unfortunately I only know what's been done to it from what I was told and I have no idea what a they specifically mean by a "big" cam, but your right to say it has a stall converter, from what I understand. How much of a headache would you say I should expect from swapping the trans? Thanks for your reply!

 

[Alf]

Jim, you mentioned that you are experiencing a delay when shifting into gear. My suggestion would be to disconnect the lower cooler line on the transmission (pressure), add a hose and run it to a bucket. Start the engine and have a friend add fluid via the dipstick tube while you slowly run it thru the gears. Watch the fluid as it goes into the bucket and turn off the engine when you see clean fluid. Drop the pan and change the filter. Buy a dozen bottles of fluid and use 'em all.
This won't fix your ratio issue but should resolve the transmission's lazyness.

 

[RifRaf]

How much of a headache would you say I should expect from swapping the trans?

Swapping from a turbo 350 to a 2004R.... or a 700r4 is pretty straight forward and not much of a headache at all.
Both overdrives bolt right up to the engine, same flywheel, you will need a new torque converter, and will have to purchase a new trans crossmember (with a 2004R)... or shorten the driveshaft (with a 700r4). You can also retain your trans cooler lines (with some slight bending at the trans). You will need a TV cable and the correct geometry corrector bracket. You may also need a new shifter (depends on what you currently have).
Just do a search on 2004R... or 700r4 swap into a 3rd gen Nova or a 1st gen Camaro (nearly same procedures for both models). There's a lot of useful information out there. I (along with other members on this forum) will also be glad to answer any questions that may come up during the swap.

If you do go this route, try to purchase an overdrive transmission from a reputable builder that can make recommendations based on your horsepower and driving goals.

 

[JimC0217]

Jim, you mentioned that you are experiencing a delay when shifting into gear. My suggestion would be to disconnect the lower cooler line on the transmission (pressure), add a hose and run it to a bucket. Start the engine and have a friend add fluid via the dipstick tube while you slowly run it thru the gears. Watch the fluid as it goes into the bucket and turn off the engine when you see clean fluid. Drop the pan and change the filter. Buy a dozen bottles of fluid and use 'em all.
This won't fix your ratio issue but should resolve the transmission's lazyness.

Thank you, had my suspicions about the filter but it has been changed to an external cooler, same principle?

 

[Alf]

Yes, same thing. Pull the return line off the trans as it returns from the cooler, (the line that returns back to the upper port on the trans) and stick it in the bucket. That way you will flush the cooler as well.
The color of the used fluid will be much darker. Watch for the color change as it pumps into the bucket. At that point the trans, converter and cooler are flushed.

 

[JimC0217]

Yes, same thing. Pull the return line off the trans as it returns from the cooler, (the line that returns back to the upper port on the trans) and stick it in the bucket. That way you will flush the cooler as well.
The color of the used fluid will be much darker. Watch for the color change as it pumps into the bucket. At that point the trans, converter and cooler are flushed.

Ok, thanks for your help!

 

[Redrider66SS]

jimc..... here is a link to a gear,rpm,speed calculator. you will have to have some known numbers to work it or just put in numbers to see what might be the gears you want for finally rpm's

Gearing Calculator | RPM and Tire Diameter to km/h - mph with Shift Tracer

www.blocklayer.com

 

[Corbinstein]

My suggestion is to get a Tach to determine exactly what you are looking at RPM wise. IF it is over revving at speed for sure, try disconnecting the Kick-Down at the carb temporarily to see if the problem suddenly goes away. it's possible you may not be actually getting into 3rd. My car did it and I disconnected the Kick-Down and just hand shift when I want to pass, etc. It's a temporary solution that has morphed into permanence on mine.

 

[JimC0217]

My suggestion is to get a Tach to determine exactly what you are looking at RPM wise. IF it is over revving at speed for sure, try disconnecting the Kick-Down at the carb temporarily to see if the problem suddenly goes away. it's possible you may not be actually getting into 3rd. My car did it and I disconnected the Kick-Down and just hand shift when I want to pass, etc. It's a temporary solution that has morphed into permanence on mine.

Makes sense, thank you!

 

[Cvy210]

Hey all, new to the forum and new to the Nova, just need some input if anyone can help. '74 350, 30 over, big cam, 373 gearing and I believe the original 350 trans. I was told when I bought the car the gears were swapped from a 4.10 to a 3.73 ratio so it will ride easy at highway speeds, because of the engine work. Finally got the car on the road, has trouble going in to gear at times but shifts fine, but the RPMs seem wound pretty tight just at 50 mph. Could this be a mechanical issue or is the trans/gearing ratio just all wrong? Thanks for any help!

Welcome. I had the same set up in 68 nova. With the 3:73. Your RPM’s are going to rev hi what I did put Tranny with over drive cleared up problem. Then you have best of both worlds could still drag / Cruise