Hey guys HAPPY HOLLIDAYS! Need some help on what to change on my 68 camaro, I have a 327 engine with alot of after market parts on it I bought it as is but I have drove my car on the HWY and my car feels hard on the engine, I have a 2 speed trans and it has a shift kit also. At 65 mph the rpm is at 4000-4200, I'm confuse here I don't know if I should fix my rear end, it's a 10 bolt and it's stock (I think) or if I should change my trans? If I change my rearend what gears should I get? Or should I change my tranny what should I look for, my tranny now is auto and I want to keep it that way.
What should I change?:yes:

Best solution would be an overdrive manual or automatic transmission.

Sounds like some really low gears, I would put the rear of the car on jack stands, put the car in neutral, put a mark on the drive shaft and a mark on the wheel ( the one that turns if its not a posi) count the number of turns that the drive shaft turns compaired to the number the wheels turn ie: 4:56

Any suggestions on the rear end? should I have it possi or keep it the same?

It sounds like you have 4:56 gears.
There are three different carriers (positraction), the difference is the lower the ratio, the smaller the pinion gear diameter, this requires the ring gear to be positioned more to the right the lower the ratio. There is a 2, 3, and 4 series carrier for ratios starting with that number.
To install 4:56 gears, you either need a 4 series carrier (posi) or a 3 series carrier and an aftermarket ring gear spacer with longer ring gear bolts. These spacers were sold to allow lower gears without having to buy a new carrier.

The reason I mention this is, your low gears either have a 4 series carrier with no spacer, or a 3 series carrier with spacer. You need to look and see what you have before ordering new gears.

If you have the 3 series carrier you can remove the spacer ring, and install any ratio from 3.08, to 3.73. If you have the 4 series carrier, you can only go to a 4.10 gear ratio, you will need to buy a 3 series carrier. If you don't have positraction, get an Eaton posi unit. Your axles may need to be replaced too. Camaro outer axle bearings ride right on the axle, the axle is the inner "race) of the bearing, so may be pitted. Just allow for extra costs like this.
David

I'd change the trans over to a TH-350 and add a set of 3. something gears if I planned on driving it on the freeway at all.Sure an overdrive would be better for the freeway, but more expensive.

Is it more race car or street car?

What size converter ?

I have a 10" 3000 stall which runs 3000 basicly at anything below 65mph. Maybe there's something there but I would still look to see what gears you have.

I had a TH400 and some really short gears. I didn't understand how someone could operate gears THIS short!! It would be near 4k around 30 mph.
Then I realized that the tranny was never really shifting into 3rd. Turns out, I do have short gears, 4:88's but not THAT short.

The tranny was never shifting despite my putting it into 3rd, it never came out of 2nd.

Your tranny might not be going into high gear for a variety of reasons. Vacuum modulator, shift linkage or maybe, as was in my case, 3rd gear was just hammered. A tranny rebuild fixed all.

Doug,
Are you saying your 3000 stall runs at 3k no matter what speed you are going below 65mph? My 3000 stall will run at about 2200 at 45 mph and varies rpm with speed. It will flash to around 3500 but has no problem running at lower rpms. You must have a very loose converter.
When take off from a dead stop does it go to 3000rpm to start moving?

If it's shifting, your gears are way too big. I would suggest 3.42's but it must be taken apart before anything to see what you have behind the cover.


On converter, my 3200 will move the car at idle if I let off the brake, will climb the driveway (30% grade) under 1200 rpm and will cruise at whatever rpm, usually 2200, but will flash immediately to 32-3500 rpm whenever I hit the throttle.

First of all. How tall is your rear tires? A trans change would not make a difference in your hwy. speed/RPM. Trans missions like you have are a 1 to 1 ratio in high gear anyway. Marking the drive shaft and tire is a quick easy way to determine the gear ratio. 4200 in high gear is a lot!!! Depending on what 10-bolt you have there are gear ratios availible up to a 5:57. Unless you have a very short rear tire I would imagine you have a 4:88 gear. Also, I am very suspect that anyone would use such low gears such as a 4:56 in a car with a 10-bolt rear. It takes a pretty stout engine to use a the gearing you are suspect of having and performing with it. Its nice to get your cruise RPM for hwy use down to 2200-2500 to run 65-70 mph and not taxing the engine and getting that dreadful loss of gas mileage. Just for grins measure your rear tire and post the height please. good luck....

Bob, not that bad... but ??? 30mph and up is 3000 or so and at about 65mph tightens up.

Frank, I have 20's on the back and 18's on the front. I don't know what gears I have, But maybe that's the problem. I really like that look on it so I dont want to change it. Any suggestions?

What is height of your tires on the rear.

My tires are 235/45/20 on the rear, I will say 26'total?

Tire = 28.3
MPH = 65
RPM = 4100
Trans ratio = 1:1
Converter slip = 8.8%

Currrent rear gear = 4.88

A 3.42 rear gear would drop to right under 3000 rpm at the same speed. An overdrive trans would help lower the rpm more. Depending on how the engine is built, too high of rear gear could kill the power badly.

Ray, The engine is built with 202 valves 58cc chambers, forged flat top pistons and a cam LOP.680 Holly carb and a Edlebrock air gap intake I bought the car like that, just rebuilt. I want to get all the power I should get from this engine . so go with the 3:42? posi?

You have to decide which is more important. Big gear = better acceleration = more rpm on the freeway. A 3.42 gear is a decent compromise if much long distance driving is in the picture, but performance does suffer some. 327's like to rev up to make power. A 3.73 gear is more performance oriented gear but would work well with the 28" tire combo.

3.08 = 2600 RPM @ 65 MPH
3.42 = 2880 RPM @ 65 MPH
3.73 = 3150 RPM @ 65 MPH
4.11 = 3460 RPM @ 65 MPH

You want an Eaton posi unit. They work great on the street for traction and drivability. If it was my choice, I would go Eaton posi and 3.73 gear with the 28" tire.

A trans swap later down the road would have benefits also. The 2-speed is not the best compromise trans. The first gear is much higher than in a 3 or 4 speed. A 200r4 would be a good trans as it is over-drive and still has a decent 1st gear. The 700r4 is good also but has a real low 1st gear.

I took my car to the shop today, to get my gears install they told me I have 3:08 gears, I'm getting a Eaton posi for sure install this Tues. I guess I will have to stay with the 3:08 and just get the posi installed and get a trans? I'm paying $700 to get the posi installed is that a good price? I dont know nothing about rear ends.Or should I change the gears to a different gear ratio?

If that includes the posi price, not too bad.

If you have 3.08's, your trans isn't shifting into high gear. You're cruising in low. Linkage could be the cause along with a few other things. Make sure you get that checked out also.

The 3.08's are a good highway gear.

I took my car to the shop today, to get my gears install they told me I have 3:08 gears, I'm getting a Eaton posi for sure install this Tues. I guess I will have to stay with the 3:08 and just get the posi installed and get a trans? I'm paying $700 to get the posi installed is that a good price? I dont know nothing about rear ends.Or should I change the gears to a different gear ratio?

Whew! The first option I ordered for my car was 4:10 posi. As I recall, the cost was $42.00. And that was with a 12 bolt-high impact set of gears. Now it's $700 for 3:08's!

$700 out the door, new seals and evrything else. I will have it installed this Tuesday and then I'll take it to have it check out to a transmission shop. Thanks for your help!

$700 out the door, new seals and evrything else. I will have it installed this Tuesday and then I'll take it to have it check out to a transmission shop. Thanks for your help!

Call the BBB and other consumer agencies before going to a tranny shop. I've found that usually, their goal is to sell you a new tranny. So If you go in wanting a new tranny anyway well...........

But if you just have a lingage problem, that is all you want to pay for. They know you don't know and may try to take advantage. A 200 dollar fix could be turned into a 2k new tranny if they are untrustworthy.

I found an honest shop here in my area and I treat them like kings. They do good work for competitive prices but I KNOW they aren't taking me for a ride. For a shop like that, I'm happy to pay because I know they're honest.
I've been taken to the cleaners by tranny shops before. Just buyer beware.

2-speed trannies are dinosaurs, heheh. As stated, make sure the thing is shifting. It could easily be something as simple as a broken vacuum line or adjustment of linkage. Are you certain the tranny is shifting? Just doesn't sound right that someone would build a street car running in excess of 4,000 rpm at 65mph. This means your top speed is not much over 100mph........ I mean, I could understand if it was a 7,000rpm race engine, but not an average street car.

I got my posi installed and it makes a big difference, well I haven't taken the car to a tranny shop. I'm asking around for a good shop.

I got my posi installed and it makes a big difference, well I haven't taken the car to a tranny shop. I'm asking around for a good shop.

Do you feel it making the 1-2 shift? Try putting in in L1 and then about 35mph shift it into H2. You should be able to feel the shift.

You should be taching about 2600 rpm at 65 mph with 3.08's.