[spb350]

I am just getting my 69 firebird on the road, test driving and working out all the issues. One of the first things I thought I was going to do was change out the rear gears. My car came with a T400 and 2:56 gears (posi) but I converted it over to a M20. Other then the slow 1st gear take off I really like the 2:56's, from 3000 to 4500 it really flies and at 70 mph (might be off a little) my tach is at 2500. The original 400 was dyno'ed and is putting out about 410HP and 500fttq so it has plenty of power, 2nd and 3rd gears are in a great torque range for around town and of course 4th on the hwy is great. I think eventually I will change the rear end to an Eaton and 3:36"s or 3:55's but for now I'm liking them. Anybody else have a similar setup and has gone long term with the 2:56's? any issues like clutch wear? Thanks

[old66tiger]

Richmond 5 speed with a 1:1 5th gear would be perfect. Low drive line speeds and will pull out of the hole very well.

[Skip Fix]

I swapped my TA's 2.56 rear in the Camaro body and I could idle it seemed at 30 mph with the 81 Z28 4 speed tranny!

Whne it was in the TA the stock 180 HP motor could only pull 4000 in high gear-but that was about 130 mph.

A buddy in college swapped a 2.56ish station wagon rear in his 64 GTO to get better gas mileage. Sluggish in first but helped gas mileage for a poor college student.

[Tom Vaught]

Originally Posted by Skip Fix

A buddy in college swapped a 2.56ish station wagon rear in his 64 GTO to get better gas mileage. Sluggish in first but helped gas mileage for a poor college student.

When I was just running around town (strictly controlled 35 MPH speed limits in Kazoo, Michigan) I ran a 4.33 Posi rear axle with 26" tall tires. Easy on the clutch and aluminum flywheel I ran.

When I was going on a long trip, I would swap out the whole 10 bolt Housing (minus axle shafts and brake parts) for a 2.56 single wheel open rear axle. Great F.E. and high cruise speed capability. Could do the swap in about 2 hrs at my uncle's Pontiac dealership.

Then I spent some money and bought a Doug Nash 5 speed trans and went up to a 3.08 GM axle. That was a lot easier between city and highway driving. Just make a geat change with the shifter. Today I run a 2.75 gear with a Detroit "Soft Locker" in a Moser 9" A-Body housing.

With a steel 30 pound flywheel and a good clutch adjusted properly, a 2.56 rear is no issue with normal driving and a muncie 4 speed.

Tom V.

[geeteeohguy]

I am running a 2.56 posi in my '67 GTO convertible with a TH400 and a corrected speedometer. 2450rpm is 75 mph, and 3000 rpm is 91 mph. The car gets 20-21mpg at a steady 75-80 mph. That said, I once drove a '65 GTO with an M20 and a transplanted 2.56 rear gear, and it was kinda wild. Like 60mph in first gear. It didn't burn up the clutch, but it was doggy out of the gate. He ended up driving it from CA to MO, loaded with his entire family, and got something like 22mpg for the whole trip. 3.08 is the tallest gear Pontiac installed with a stickshift. I think you'd be ok with that, or maybe a 2.93 at the tallest. I would think twice before installing anything like a 3.55 in your car, unless you like cruising at 60mph. A 3.08 or 3.23 with your combo would be an excellent choice, IMO.

[71SportRagtop]

Funny,

When I scored my 68 Firebird it had a 4 speed and a 3:08 rear. I absolutely HATED it. I've always been a fan of steep gearing in my Musclecars. I swapped out the 3:08's for a 3:73 rear and I love it.

Keep in mind though that all my driving is local. I use my car for local Saturday night cruises, local shows, and an occasional run out for ice cream with the wife and kids. My car never sees highway driving and really never travels more than 15-20 miles from home.

[Rownbike]

I've got a 2.56 rear in my 400/4 speed right know and am in the process of swapping it out for a 3.55. It's really hard to get the car moving and I have to believe that it is hard on the clutch and engine. Had to replace the clutch last year. It too is just a weekend cruiser and rarely sees a highway or cruising speeds over 60, so the 3.55 should be fun. I'll let you know in a couple of weeks.
Mike

[461bird]

I have a 2.78 safety track rear and a 2.87 first gear tko 600 trans and it works very good. I did some research before selecting what I went with and most trans guys liked it to be between 7 and 10 when multiplying trans first gear by rear ratio for a street driven car. Pontiac motors make good torque so I stayed on the low end of their recommendation for traction purposes, still can roast the tires at will but with a little throttle control I can get it to hook up and get moving. All that really matters though is how you like it as long as you don't have the PITA of going thru clutches.

[gtofreek]

I had 2.56 gears in my 65 GTO with an M-21 4 speed, and a 428 around 400 HP. I burned up clutch's about every 2-3 month's. Had to ride the clutch too long to get going. It was great for highway cruising, but after about 6 clutch's in a couple of years, I got tired of it and found a 3.36 rearend, and put that in. Clutch's seemed to last forever then.

[Nicks67GTO]

Originally Posted by old66tiger

Richmond 5 speed with a 1:1 5th gear would be perfect. Low drive line speeds and will pull out of the hole very well.

This right here ^^^ The Richmond 4+1 1:1 tranny should bolt in, there's one for sale in the performance section right now I believe and its been for sale for a while. Sell the Muncie to a resto guy and youll be 3/4 the way there. Ive been running one for over 10 years and didnt have to touch my floor installing it in my 67 GTO, other than to modify the shifter hump a bit but that's easily fixed. My current configuration is a Moser 9" with 2.75 gears, 28" tall rear tires, and the Richmond 4+1 5 speed. It works awesome.

[1967Tempest]

My 67 Tempest wagon has 2.56 one legger and it is GREAT!!!!!


One difference is that my transmission is a Saginaw with 3.56 first gear. So when I start off the car actually moves quite well. The car is fun to drive and can annihilate the right rear tire. So I have the best of both worlds. Great off the line and 1:1 with highway gears.


It is a little weird as I can drive around in 3rd gear all day in town and the car is fine. GGet it on the highway and fourth is great!!!

I have to take a video for the wagon. I will post it here too.

Dave

[Tom Vaught]

Originally Posted by 71SportRagtop

Funny,

When I scored my 68 Firebird it had a 4 speed and a 3:08 rear. I absolutely HATED it. I've always been a fan of steep gearing in my Musclecars. I swapped out the 3:08's for a 3:73 rear and I love it.

Keep in mind though that all my driving is local. I use my car for local Saturday night cruises, local shows, and an occasional run out for ice cream with the wife and kids. My car never sees highway driving and really never travels more than 15-20 miles from home.

X2 on the city only stuff.

The 4.33 deal was maybe a bit stiff vs the 3.90 or 4.10 type stuff but was great when you hit the tri-power against a Mustang or decided to burn rubber for 3 city blocks.

Tom V.

I drove the car at highway speeds on I-94 (70+ mph) one time and except for consuming a great deal of gas (one tank full 21 gallons) in 150 miles the engine had no issues. A buddy drove a 4.56 Early Z-28 Camaro from Tennessee to Michigan and the 302 was humming.

[track73]

You could get a Saginaw or Super T-10 with a real low 1st gear. I have a 3.43 first gear T-10 that I'm mating to a 2.73 rear. I'm hoping it will be like a 3 speed with over drive. The torque of the 461 would make it very drive-able.

[spb350]

I think I will keep an eye out for a good used DN 5 speed, if I can get the tranny and other parts for a little more then the original Muncie and Hurst shifter it might be a good idea. I know if I go to an Eaton and pay someone to install it it will prbably cost me more. Do I need to swap the clutch, fly wheel or bell housing?

[Radman]

Look for a good transmission that has an overdrive as the final gear. I am working with a 700R4, yes it is an automatic. But the numbers will give you a good idea. The car is a 62 Tempest, with a 61 389, the tires are 27 inches tall (Hooser 28X9.50X15 Street Pro). At 70 MPH I am turning 2,000 RPM. I have had the car at one test and tune session at the track. In first gear I was roasting the tires if I did not feather the gas off of the line.
OK axle, gear, final drive ratio
3.50, 1st 3/1, 10.5/1
2nd 1.65/1, 5.775
3rd 1/1, 3.50
4th .7/7, 2.45

[tom s]

I have a 3.42 first ST 10 in a 62 GP with a 2.67 in the back.Have used them before and they make a great street trans.FYI,they have a very low TQ rating so big sticky tires will become a problem.Tom

[leeklm]

I did not notice if this was mentioned earlier, but you want to look at your final drive number to determine how suited the 4spd may be with your rear gear. To do that, simply add your transmission gear ratio (any gear) + your rear ratio.

For example, in Tom's post, you would add his 1st gear + rear ratio and get 6.09, which would work really well with a clutch.

From my experience, I currently have a 2.42 1st gear in my Muncie + a 3.31 rear, which is 5.73. I tried the same rear gear with a 2.20 close ratio munice, and did not like it. The final drive in this case was 5.51 in first, and required too much clutch IMO with my 27" rear tires.

Now my same wide-ratio Muncie with a 2.56 rear would be 4.98, and I personally would not like that at all, especially with a taller tire. Maybe you could get by with a 14" short tire.

[hellerods]

I just added a Muncie to my stock 256's in my 64' Catalina and the clutch and the rest of the drivetrain just can't handle it, to much chattering and slipping to get it to move, have bought and will install soon a new set of 323's. With a fresh 455 the car has plenty of power for low rpm starts, and on the freeway it flys, but for around town stop and go it sucks!!Lee

[Half-Inch Stud]

We had the 70 ATOLL blue GTO with 2.54:1 Posi type O rear, and the dearborn 3-speed.

2nd gear lasts to 70 or 80 MPH which is forever. 3rd on highway would resonate the exhaust into a loud DRONE.

pull-away was fine enough with that 3-speed & Torquey 400

[goatwgn]

Originally Posted by 1967Tempest

My 67 Tempest wagon has 2.56 one legger and it is GREAT!!!!!


One difference is that my transmission is a Saginaw with 3.56 first gear. So when I start off the car actually moves quite well. The car is fun to drive and can annihilate the right rear tire. So I have the best of both worlds. Great off the line and 1:1 with highway gears.


It is a little weird as I can drive around in 3rd gear all day in town and the car is fine. GGet it on the highway and fourth is great!!!

I have to take a video for the wagon. I will post it here too.

Dave

Ran my old 326 almost 300,000 miles with that same gear in there. It had the old St 300 slushbox behind it as well. It could downshift to first gear when you hit the gas at 70 mph. Have 3.42s in there now with a TH400/GV overdrive. Works out to close the same final drive (about 2.66). Did not care for the higher rpms on the highway with the 3.42 gears without the GV unit. It ran there fine, it just wasn't as "comfortable" as it is now. And uses a lot less fuel to boot.