[charles69]

I have a 1969 chevelle ss 396/325hp. The engine is basically stock. I use the car as my every day driver. I have owned the car for 3 months and still am learning things aboout it . It has the orginal 3.55 rear, the transmission is not original, it is a manual four speed from a 1978 trans am(I did not put this tranny in the previos owner did). I have several question. The first is how can I find out information on this transmission, for future reference? The second is I do alot of cruising, and at present I run about 3000rpm @60mph. This is alot of work for my engine to do. What I want to know is what would be a good combination for cruising alot , I would like a combination thaat pulls low rpms at highway speeds. Should I change rears? Maybe transmissions? Maybe both? I would appreciate all comments, and please share the combinations tou are running, I would like to know. Thank you in advanced.


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[Alan F]

I've got the same rear gears with an automatic and the same dilemna. You could drop an over-driven 5 speed in there. I am going to exchange my rearend for a 3.08:1. I don't mind the 3,000 rpms, I just want to be going 70.

 

[COPO]

3,000 is nothing. If you had a Muncie M20 you would be reving the same. The trans you have is a Borg Warner Super T-10 that the 77-81 Z28 and Trans Ams used. It's a good choice if you don't have a Muncie. If you change the rear gears to a lower numerical number then you won't have any balls on the street. I had a M20 with my 4.10:1 and didn't like the high revs in town. I'd sometimes shift to 4th if I was going 40+. I removed my M20 gears and replaced them with M22 gears, plus I wanted the sound of the M22 whine. On the highway in 4th at 70mph I am reving almost 4,000 rpm with my LT1. I would keep what you have, unless you want the Muncie for originality.

Mark

 

[Gene Chas]

How much $$ do you want to spend? You could put in an auto/OD trans and get a bit more low and topend. You could drop your rear to 308 and get your cruise rpm down, etc., etc., etc. I recommend you check out Wes Vanns' Tech Reference on this site. He goes through a bunch of calculations and comparisons you might find helpful. My ideal setup would be a Richmond ( or old Nash ) five sp with my 3.31's. It would give me a 1st and 2nd gear like a Muncie with 4.88's ( YEAH!) and a final drive of 3.3 which is ok for the open road. But I want a "wheels up" launch and am not too concerned with going 85 on the highway. The same tranny with 2.73's would suit you fine. Check out Wes's work, it'll give you good food for thought. For a daily driver, where I'm not worried about ripping the s&%@ out of a 5.0 Mustang off the line, I'd put in 308's.

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[This message has been edited by Gene Chas (edited 05-19-99).]

 

[Jim Elliott]

Hi
Looking at my chart and if your tach is correct you have a tire size 24" tall. By switching to a 235-70-15 tire the height is approx 28" tall and will bring down your rpm's to 2559

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[Jim Elliott]

Hi
Looking at my chart and if your tach is correct you have a tire size 24" tall. By switching to a 235-70-15 tire the height is approx 28" tall and will bring down your rpm's to 2559

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[DZAUTO]

I have a 70 conv with a SB400, wide Muncie (M20) and 3.08 gear. At 78mph the tach is 3000. I like this combo. Yes, off the line is a little slow, but boy does it wind out through the gears. By the time I hit 4th, it's out there!

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[Bob Tiley]

In my opinion the 3.55 rear gear is the best for around town cruising and highway use. My 4.10 gears are a little steep on the highway but that does not stop me from driving 2 hours to a good Chevelle Show. The transmission from the 78 Trans Am is the Borg Warner Super T-10 and it is a very good 4-speed box.
The easiest option is to switch to a set of 15" tires and wheels.