5 or 6 speed manual transmission for a 77

[Russell Fulks]

All,

I have a 77 that is heavily modified so will not ever be judged. I thought about restoring it to original but the expense is too great considering the current state of modification and my pocket book. What I do want to do is drive and enjoy my car! The L-82 engine and 4 speed manual transmission are good for about 5000 rpm at 80 mph. I live in Houston where 80 mph is about as slow as anyone drives.

I was wondering if there is a 5 or 6 speed "overdrive" type of manual transmission that will fit in my 77 L82 car. If anyone has any experiences with something similar I would appreciate any help on the matter.

Thanks,

Russ Fulks

[Michael W.]

You want to go after your diff., not your

transmission if you're really turning 5K at 80 MPH. What ratio have you got? Think maybe about a 3.36, that's what your car orignally came with I believe.

[Michael W.]

You want to go after your diff., not your

transmission if you're really turning 5K at 80 MPH. What ratio have you got? Think maybe about a 3.36, that's what your car orignally came with I believe.

[Russell Fulks]

Re: You want to go after your diff., not your

Unfortunately, I don't know what diff. I have. I am going to get the rear end up this weekend and turn the wheels and count how many turns it takes to get 1 revolution on the drive shaft. That should give me a ballpark estimate.

The problem is that I don't really want to loose the lowend "go" power by swapping out the differential. In order to turn a more reasonable 3000-3500 at 80 mph, it would take me 1/2 an hour to get there because the low end torque and acceleration would be so bad. At least that's what the mechanic here in town thinks.

[Russell Fulks]

Re: You want to go after your diff., not your

Unfortunately, I don't know what diff. I have. I am going to get the rear end up this weekend and turn the wheels and count how many turns it takes to get 1 revolution on the drive shaft. That should give me a ballpark estimate.

The problem is that I don't really want to loose the lowend "go" power by swapping out the differential. In order to turn a more reasonable 3000-3500 at 80 mph, it would take me 1/2 an hour to get there because the low end torque and acceleration would be so bad. At least that's what the mechanic here in town thinks.

[Duke W.]

Re: 5 or 6 speed manual transmission for a 77

I believe the shortest available rear axle ratio on your year L-82 was 3.70:1, and with the OEM tires of about 760 revs per mile the revs at 60 should be 3.7 x 760 = 2812, and about 3750 at 80.

The easiest (non-OEM) tranmission swap is a Richmond five-speed with has a 3.28 first and a 1:1 fifth, and it would work very well with a 3.08 gear. They also make a six speed, with an overdrive sixth, but six gears is way overkill.

You should first verify what axle ratio you actually have by counting turns, then pull your speedometer driven gear and note the color and number of teeth. Also note the color of the drive gear in the gearbox. Find a speedometer check section on a highway, or go to a shop that can test it. I suspect that something is out of bounds in your speedometer or tach calibration. Also, what size tires are you running?

Figure out what you have first, then research the other available power teams of that era. A wide ratio gearbox with the 3.36 or 3.08 would be both a cheaper swap and easier to do.

Duke

[Duke W.]

Re: 5 or 6 speed manual transmission for a 77

I believe the shortest available rear axle ratio on your year L-82 was 3.70:1, and with the OEM tires of about 760 revs per mile the revs at 60 should be 3.7 x 760 = 2812, and about 3750 at 80.

The easiest (non-OEM) tranmission swap is a Richmond five-speed with has a 3.28 first and a 1:1 fifth, and it would work very well with a 3.08 gear. They also make a six speed, with an overdrive sixth, but six gears is way overkill.

You should first verify what axle ratio you actually have by counting turns, then pull your speedometer driven gear and note the color and number of teeth. Also note the color of the drive gear in the gearbox. Find a speedometer check section on a highway, or go to a shop that can test it. I suspect that something is out of bounds in your speedometer or tach calibration. Also, what size tires are you running?

Figure out what you have first, then research the other available power teams of that era. A wide ratio gearbox with the 3.36 or 3.08 would be both a cheaper swap and easier to do.

Duke

[Ed Jennings]

Re: 5 or 6 speed manual transmission for a 77

Duke gives excellent advice as usual. Another point to consider: If you are indeed turning something like 5 grand at 80 MPH, you must have a differential ratio of 4.56:1 or better. I haven't calculated that, but it would have to be a very high (numerically) ratio. If you were to install a .5:1 overdrive, your final drive would be on the order of 2.23:1. I suspect that this gearing would give you very anemic performance on the highway. I have driven cars with 2.73's that were positively dogs as far as high speed acceleration went, and if you dropped down a gear the wide change in RPM wasn't allthat great a sensation either. An L82 shouldn't be all that anemic with a 3.36 or a 3.55 in anything like normal, adult driving. I guess anemic is a subjective thing.

[Ed Jennings]

Re: 5 or 6 speed manual transmission for a 77

Duke gives excellent advice as usual. Another point to consider: If you are indeed turning something like 5 grand at 80 MPH, you must have a differential ratio of 4.56:1 or better. I haven't calculated that, but it would have to be a very high (numerically) ratio. If you were to install a .5:1 overdrive, your final drive would be on the order of 2.23:1. I suspect that this gearing would give you very anemic performance on the highway. I have driven cars with 2.73's that were positively dogs as far as high speed acceleration went, and if you dropped down a gear the wide change in RPM wasn't allthat great a sensation either. An L82 shouldn't be all that anemic with a 3.36 or a 3.55 in anything like normal, adult driving. I guess anemic is a subjective thing.

[Jack layton #896]

Re: 5 or 6 speed manual transmission for a 77

www.muncie4speed.com
Try these guys for a gear set which has a very low 1st gear in a very wide ratio box. I remember that the 1980 Z-28's used a very low first gear to give them some launch with their smog/low horsepower engines. It may have been a 2.74 or some such ratio. Then combined with a 3.36 rear in a much lighter car(Corvette) this would give you both ends of the spectrum.
Modifying your Muncie would seem to be easier than adapting a Richmond trans. And who really wants to shift 6 times in a street car? I bet most of us only use 3 gears in our 4-spds. 1-2-4 or 1-3-4 around town.

[Jack layton #896]

Re: 5 or 6 speed manual transmission for a 77

www.muncie4speed.com
Try these guys for a gear set which has a very low 1st gear in a very wide ratio box. I remember that the 1980 Z-28's used a very low first gear to give them some launch with their smog/low horsepower engines. It may have been a 2.74 or some such ratio. Then combined with a 3.36 rear in a much lighter car(Corvette) this would give you both ends of the spectrum.
Modifying your Muncie would seem to be easier than adapting a Richmond trans. And who really wants to shift 6 times in a street car? I bet most of us only use 3 gears in our 4-spds. 1-2-4 or 1-3-4 around town.

[Russell Fulks]

Re: 5 or 6 speed manual transmission for a 77

All,

Thanks for all of the info. I am going to count the ratio this weekend to see approx. what gearing I have in the rearend. I have a blue drive gear in the transmission and was missing the driven gear. I had to buy about 3 different driven gears until I finally found the gear that showed a 1 minute mile at 60mph. The actual numbers are ~4750rpm at ~81mph. It sounds like a wider gear box would be less costly and indeed easier to do. Any suggestions on where to start looking. I did note the www.muncie4speed.com website posted earlier. Is this the place to start?

Thanks again for all of your suggestions.

Russ Fulks

[Russell Fulks]

Re: 5 or 6 speed manual transmission for a 77

All,

Thanks for all of the info. I am going to count the ratio this weekend to see approx. what gearing I have in the rearend. I have a blue drive gear in the transmission and was missing the driven gear. I had to buy about 3 different driven gears until I finally found the gear that showed a 1 minute mile at 60mph. The actual numbers are ~4750rpm at ~81mph. It sounds like a wider gear box would be less costly and indeed easier to do. Any suggestions on where to start looking. I did note the www.muncie4speed.com website posted earlier. Is this the place to start?

Thanks again for all of your suggestions.

Russ Fulks

[Grant M.]

Re: 5 or 6 speed manual transmission for a 77

I don't know about '77s, but our '78 (L48) came with a 3.55, which I believe was the standard ratio for the lower horsepower motor, to give it a little better off-the-line performance. RPM at 70 mph is about 3500.

[Grant M.]

Re: 5 or 6 speed manual transmission for a 77

I don't know about '77s, but our '78 (L48) came with a 3.55, which I believe was the standard ratio for the lower horsepower motor, to give it a little better off-the-line performance. RPM at 70 mph is about 3500.