[65madgoat]

Having set up several of my own plus countless others, a Pontiac does not need a 3.27 first gear -- so then it comes down to OD desired.

Either .68 or .81

Dropping over 30% from 4th gear is not ideal. The .81 is just right as long as set up with no more than 3.55 gears with 3.42 being a great choice

[jhein]

The choices you have it narrowed down to are so close I don't see any benefit from the wide ratio. Given those two options I'd go close ratio with the 3.73.

[65madgoat]

American Powertrain is the best to get from by the way and their shifter is top notch compared to others. They sell and set up more cars with the 2.87 first gear trans.

So now OD option is your choice - either .68 or .81 -- choose according to rear end gear selected and highway use expected.

But again, 3:55 usually great common ground in a Pontiac. The LS guys with less torque go 3:73 rear gear.

3:42 (or 3:55) rear gear and .81 OD hard to beat for you I believe with 2.87 first gear trans.

[Formulajones]

Shucks I use the .64 in 2 different cars, both with 302's and I find even those little engines don't complain. One with 3.55's and the other with 3.73's. I don't even need to downshift from 5th pulling the mountain grades around here so a Pontiac shouldn't even notice it.

[Formulajones]

Originally Posted by PontiacMatt72

A lot of great feedback, thanks everyone! It’s funny though, there have been 22 “votes” cast in the poll for this thread as of 8:45am Oct 31. I’ve attached a screenshot of the current results. (Three of the choices each have an equal 6 votes, and the fourth option isn’t far behind with 4).

Obviously any of these choices are a drastic improvement to what I’ve dealt with as far as the first gear situation. The upside to the M20 and 2.93 rear gear is I can keep right up with interstate/highway traffic effortlessly. But around town is tricky.

How do I drive the car is the question that everyone keeps going back to, and I understand why. But that’s tough, because I drive it in a lot of scenarios. From occasional parades to hot rod power tour (this past year). HRPT consists of pretty much all driving conditions - stop and go traffic to interstate routes. And, I’ve been equipping the car with suspension and braking components that would support occasional autocross. I’ve not competed in any autocross events ever, just considering trying it out. But this will not be a dedicated autocross car.

Can’t have it all, I’m fully aware there will have to be sacrifice somewhere.

I think I’ve narrowed it down though to two options: the wide ratio TKX (.72 OD) with the 3.31 gear, or the close ratio TKX (.68 OD) with the 3.73 gear.

Effective first gear ratios:
Wide/3.31 = 3.27 x 3.31 = 10.82
Close/3.73 = 2.87 x 3.73 = 10.70

Cruise speed RPMs:
60mph
Wide/3.31 = 1,807 rpm
Close/3.73 = 1,923 rpm

75mph
Wide/3.31 = 2,259 rpm
Close/3.73 = 2,404 rpm

I can easily deal with cruising rpms up to around 2,500. That’s a non-issue for me.

Is there any secret formula to decide on between the wide or close ratio trans?

Yes there is. The 2.87 trans you're thinking about with 3.73's has better gear multipication through the gears. Meaning 2nd through 4th are much better so you gain better/easier acceleration going through the gears.
The 3.27 trans with the 3.31's you mentioned is going to be a bit soggier 2nd through 4th. This is something many don't take into consideration but it does make a big difference in drivability as well. Slowing to turn corners, slow rolls etc.... the 3.27 trans with 3.31's is going to have you looking for 2nd gear all the time where the 2.87 with 3.73's does it in 3rd, so there is less shifting involved.

Many people don't consider this because these are weekend toys, but when you drive them day in and day out like I do, or you plan those big trips you're talking about like power tour, you're going to notice those differences pretty quickly.

[PontiacHO]

Any choices you’ve presented are going to be a really short 1st gear. For street use you’ll be shifting into second about as soon as the car starts rolling.. The M20 and 3.31 would be more enjoyable in my opinion.

[Formulajones]

What are you guys shifting at? lol

The 2.87 with 3.73's rolls out nicely, I get completely through an intersection before I'm looking for 2nd gear, yet it's still nice enough you don't need a bunch of clutch to get moving, and no need to keep clutching it in traffic. The M20 with 2.73's is absolutely horrible in that scenario, as the op has already pointed out.

The only car I complained about 1st being too short is the bug with it's 3.80 first gear and 4.37 ring and pinion. You want to talk about short, Now that's SHORT

I changed that one to 3.44's and a 3.88 ring and pinion when the big motor went in.

[soupman]

I have the close ratio and many times if I don’t come to a complete stop, and just moving about 5 mph, I don’t bother with 1st. I just use 2nd gear to accelerate away from an almost complete stop.

[Formulajones]

I do that with most of our stick cars, mainly to just save a shift

[jhein]

Why are stick guys so not into shifting gears? There's a reason why there are 5 of them in a TKX. You're supposed to use them. Otherwise, just put in a powerglide and be done with it.

[Formulajones]

We daily them, they aren't just weekend toys for our family.

[scott70]

I’m still waiting for a driveshaft to get delivered so I can try out my close ratio tkx with .81 OD with a 3.31 rear. My m21 has 2.20 1st gear and was decent to drive around but would be much better with a steeper 1st gear. I think this new setup will be much more pleasurable to drive and also help with my 60 fts. at the track. .81 of should knock the rpms down around 550 rpm’s at 60 mph. All sounds good to me. Why Pontiac didn’t put the m20 in the 455 70 gto is weird. The 2.20 with a mild rear sucks. I wouldn’t go close ratio tkx and a 3.73 rear… don’t think you need it that steep.

[jhein]

Originally Posted by scott70

I’m still waiting for a driveshaft to get delivered so I can try out my close ratio tkx with .81 OD with a 3.31 rear. My m21 has 2.20 1st gear and was decent to drive around but would be much better with a steeper 1st gear. I think this new setup will be much more pleasurable to drive and also help with my 60 fts. at the track. .81 of should knock the rpms down around 550 rpm’s at 60 mph. All sounds good to me. Why Pontiac didn’t put the m20 in the 455 70 gto is weird. The 2.20 with a mild rear sucks. I wouldn’t go close ratio tkx and a 3.73 rear… don’t think you need it that steep.

Obviously, that's the set up that I have. I think it's near perfect. It's like having a M20 with a 3.77 rear gear in first and 2.68 rear gear in 4th. I think you're gonna love it.

[Bill S]

Originally Posted by PontiacMatt72

After developing a noise in my 70 GTO M20 transmission, I discovered a broken gear tooth on first gear.

Have you looked into the Gears Vendor option (fixing your M20 at the same time)?

The idea sounds good: kept my excellent shifting Hurst shifter, no need to change the clutch., .78 OD, can clutch shift into "second gear (1st gear OD). Not sure how good the GV unit is, or other install issues.
Talking from a street driving perspective, not track car.
https://www.gearvendors.com/hrgm4sm.html

[scott70]

Originally Posted by jhein

Obviously, that's the set up that I have. I think it's near perfect. It's like having a M20 with a 3.77 rear gear in first and 2.68 rear gear in 4th. I think you're gonna love it.

Actually got a email today… dennys driveshaft shipped today. Sounds like a good combination for the OP.

[jhein]

Originally Posted by scott70

Actually got a email today… dennys driveshaft shipped today. Sounds like a good combination for the OP.

Yeah I thought about that too. I was just wondering about the fact that the OPs motor is a stockish 400. So I thought that may tolerate a 2.87 1st gear with a 3.73 rear a little better.

[The Champ]

Originally Posted by jhein

Yeah I thought about that too. I was just wondering about the fact that the OPs motor is a stockish 400. So I thought that may tolerate a 2.87 1st gear with a 3.73 rear a little better.

The OP has been driving his GTO with a 2.52 first gear and a 2.93 rear gear (effective 7.4 ratio).

I think a 2.87 first gear alone would be more than 'tolerable', even with the current 2.93 rear (8.4 effective ratio - a 12% improvement).

Going to a 3.73 rear would take a major change in his driving habits to avoid doing burnouts from every stop sign/stop light.

[PontiacMatt72]

I agree, any way ya shake it, this will be different, in a good way. But, it’s nothing I can’t handle.

I frequently get the opportunity to drive a 2015 Camaro SS 6-speed car. It has a 3.01 first with a 3.45 rear gear. That math comes out to a 10.38 effective first gear. Of course, it also has traction control, and I believe a 315 tire in the back… but point is, I can adjust, and probably avoid the inadvertent burnouts. 😎

I may consider the 3.55 rear gear with the close ratio… still a good first gear ratio (10.18) and (of course) slightly lower cruising rpm’s (60mph = 1,830 / 75mph = 2288). Although, for whatever reason, that’s the least voted for option in the poll… if I trust the poll, the “best” option would be the wide ratio trans with the 3.31 rear gear. Hmmm

[jhein]

Don't listen to me or anyone else. The poll was fun to see what others think, and it was quite interesting. The fact that it was essentially even between all the options means that there is no right answer for everyone. Choose the one that YOU think fits YOUR driving in YOUR car.

[Formulajones]

Originally Posted by PontiacMatt72

I agree, any way ya shake it, this will be different, in a good way. But, it’s nothing I can’t handle.

I frequently get the opportunity to drive a 2015 Camaro SS 6-speed car. It has a 3.01 first with a 3.45 rear gear. That math comes out to a 10.38 effective first gear. Of course, it also has traction control, and I believe a 315 tire in the back… but point is, I can adjust, and probably avoid the inadvertent burnouts. 😎

I may consider the 3.55 rear gear with the close ratio… still a good first gear ratio (10.18) and (of course) slightly lower cruising rpm’s (60mph = 1,830 / 75mph = 2288). Although, for whatever reason, that’s the least voted for option in the poll… if I trust the poll, the “best” option would be the wide ratio trans with the 3.31 rear gear. Hmmm

I didn't even look at the poll, I just give my experiences with the the options you posted and why. As I mentioned, I use the 2.87 with 3.55's in one of the cars, with a .64 5th and it's a pleasure to drive. No reason it wouldn't be. Nice easy cruising on the interstates for the long trips. Every one I've ever swapped in I hear the same thing, "best money I've ever spent on the car" or "don't know why I didn't do this sooner" etc..... You'll be happy with either option.
The most likely reason your poll shows the 3.27 as a favorite is simply because most people on this forum don't have much rear gear in their cars, and the simple answer is they don't want to bother changing rear gears, it's expensive to do it right, takes special tools, and most can't do it themselves anyway and would have to pay a shop, so rather than dig into a rearend change, they opt for a steep 1st gear to basically avoid that deal. It's an extremely small sample rate on the forum here that really won't represent the vast majority.