[indetrucks]

I'm looking to put a little more mellow gearing in my 67 GTO.

It has 4.10's in it now with a Muncie 4spd (not sure which one) and posi-traction. PHS shows the posi was factory and it is the 10 bolt, but clearly the gears are not stock.

I don't do any freeway (highway/motorway) driving so speeds tend to be 45mph around town. The car is comfortable at 45mpg but anything over and the rpm's get up there.

I'd rather be comfortable at around 55 mph but no necessarily highway specific gearing as I really like the low end oomph

1) What gears should I go with? 3.73?
2) Where is the best place to order these gears?

[67GTONUT]

IMHO....

If you never intend to put a 5/6 speed in it..... then I would do 3.55's

If there is a chance of 5/6 speed in the future.... then I would do 3.73's

[indetrucks]

No, will be keeping the stock 4spd in it.

Would I gain at least 10mph cruising speed if I went from my current 4.10's to 3.55's?

[67GTONUT]

http://www.advanced-ev.com/Calculato...?tire_dia=26.0

Looks like at 45mph, you are at about 2400rpms with a 26" tall tire with the 4.10's

would drop to:

2100 rpms @ 45mph or 53mph @ the original 2400rpms with the 3.55's

I have 3.36's in mine.... which gives me 55mph @ 2400rpms

[merlotgoat]

Love my 3:36 gears for all around driving, but if I did a lot of long-distance highway driving I would go with taller gears just to get the revs down a bit.

[AG]

Switching to 3.55s would make you go 52 mph at the same rpm you are going 45 mph at with the 4.10s.

[geeteeohguy]

3.55's were the common ratio for 4 speed cars. I hate them on the street, but that's just me. They cruise at 55 mph, and start to get busy at 60mph. I changed the 3.55's in my '65 to 3.36's, because that was as low as I could go with my carrier (same one you have). Car is responsive around town, and fun, but will now cruise at 70mph. These cars have so much torque that a high gear is not needed. Who wants to be in fourth gear at 35 mph???

['ol Pinion head]

indetrucks, might measure current tire height & calculate engine rpm @ 50, 60, & 70 mph.
Read your post & realize the GTO will mainly be driven in town. Agree with geeteeoguy! With a wide ratio Muncie, short tires (24.5-25.5" tall), the 3.36's may be a better choice than the 3.55's esp if you end up getting out on the freeway some. With a taller tire: 255-60's or 275-60-15's, 3.55's could still make it out on the freeway... a little.

For 3.36's or 3.55's can purchase new Yukons from Randy's or Summit. Also, those ratios are avail in Richmonds. Have had better experience with the Richmond 8.2 Pontiac gears than I have with Richmond 8.5's... refuse to install their 8.5's.

For 3.73's, believe those are a Motive only deal, & am currently out on Motives, until get a ton more quality* feedback on Motive Pontiac 8.2 gears in quiet cruiser type Pontiacs.

* owners that are half deaf & have flowmaster 40's under their car, usually not going to get very good feedback on r/e gear whine/noise

[66 Gas Tires Oil]

right now do you know if you got the correct speedometer drive gear in the muncie. if not your mph may be different than you think. maybe check it against a gps mph indicator. after you get you new gears picked out intall the correct speedometer gear it is easy to do and get a new seal all for around $10. and installs easy.

Jim

[indetrucks]

Originally Posted by 66 Gas Tires Oil

right now do you know if you got the correct speedometer drive gear in the muncie. if not your mph may be different than you think. maybe check it against a gps mph indicator. after you get you new gears picked out intall the correct speedometer gear it is easy to do and get a new seal all for around $10. and installs easy.

Jim

Good point... my speedo is def. off and I assumed 45mph based on the speed limit and the cars around me.

I'll run the GPS next time.
It sounds like 3:55's are the way to go.

[GT182]

Inde, if you go with 3:55s also go with at least 255/15" tires. I'm running 255/60-15 BFGs with a 3:55 rear on my GTO and they helped lower the rpms by 350 to 400.

[Nicks67GTO]

Here is an option....

If you're never going to run a slick at the racetrack you could do this.....find a 2.73 gear and install it. Sell the 4.10's. Sell the muncie/shifter. Buy an old used Richmond 1:1 5 speed and a 26 spline clutch disc with the money you get out of that muncie. Ive seen them go used for as low as $1000 with a shifter before, so there shouldnt be hardly any major expense because on the other hand....ive seen guys pay a mint for Muncies.

With the deep 1-4 gears, it will give you an effective drive ratio about the same as 3.55's and an M21 around town. Then shift into the 1:1 5th gear for pleasure cruising the interstate. This is just about identical to my current setup and a 9" ford with 2.75's and the Richmond 1:1 5 speed.

If you're worried about cutting the floors there will be no need. Use your stock crossmember and lower the mounting pad by about a 1/2" It calls for an 1/8" but this will give you room to shim up with washers and play with your driveline angle if necessary.

This is just my opinion. Of course if you have a stock console i guess this wont work without a custom stick and even then im not 100% sure there is room.

Just a suggestion....

If you really want to know whats up with your speed based on gears, RPM and tire size go here http://richmondgear.com/index.php/ge...on-calculators and select the street calculator... it is a very useful tool thats very easy to use.

[Nicks67GTO]

BTW im running a 28" tall 275/60/15 and @ 75 mph im only spinning 2450rpm

[moto-d]

Got stock 3.23 posi in my '67 GTO (A/C car) with 14x6 Wide Oval redlines ... to me it's a nice combo. Keeps me at about 2100 on the highway but still gets up in town. I've got a spare 3.55 open rear end and thought about it ... but nah.

[geeteeohguy]

X2. 3.23 is by far my favorite all around gear for a stickshift GTO. Have owned several of them and they do everything well.

[Doug]

It is unclear about whether or not your tranny is wide or close ratio. (Either one would have the same 4th gear so road speed/engine revs would be the same for both.)

I'm guessing you have a wide-ratio so I suggest you buy yourself a complete rear-end with 3.23 gears and switch out the complete rear-end. Since you like the feeling of oomph the 3.23 will be "responsive" enough. I doubt you really need a posi for your
street driving so an open 3.23 would work ok.

You could keep your complete 4.10 posi rear-end and switch it back in if you ever want to.

I ran a 65 GTO wide ratio using a complete 3.90 posi rear-end and a complete 3.23 open rear-end which I switched in and out as needed. Worked great.

X3 on the wide ratio with 3.23's.

[Nutts]

Hi,
If you search under my name, I've posted lots of messages on a similar thread. Essentially you need to physically check:
1) GPS actual current mph vs engine rpm. Use the gps figure when using online calculators.
2) measure your physical gear ratio - raise rear end and count revolutions of rear wheel vs prop rotations to check what you actual have. Don't assume anything just because the bloke you bought it off told you so.
3) ensure you know your actual 1st gear Muncie ratio eg 2.56 or 2.2. You may have a M20, M21 or M22, important bit is understanding your true first gear ratio which ever Muncie you have, not assuming that cos you'd gave a M20 you have 2.56, as gears can be changed. Do this by counting teeth or spinning engine and counting revolutions in 1st and doing the math. There is a post on how to do this also in my threads which works if you physically can't access the gear case to count teeth or your propshaft / rear end is off (as mine was, making it extra hard to know).
4) physically measure your rear wheel diameter when using online calculators. I have cooper cobra gt 225/70R14 tyres which physically measure 1" diameter less than what the spec says it should measure. I have no idea why, no one knows, but it all affects rpm when taking it all into consideration.
5) I have a 8.2" 10 bolt rear end in my 67 Gto which had 3.73 gears. 59mph was 3000rpm and on its limit of what was tolerable. I've now had 3.08 Richmand gears installed WHICH FITTED MY PARTICULAR CARRIER. Therefore get an expert to check what carrier you have - don't assume that cos it's a 8.2" 10 bolt your lowest gear is 3.33, which people may say.
=> key to my message is don't assume anything, measure everything. Better to get the facts and make informed decisions than assume and get it wrong!

I live in uk so our decent roads are 60-80mph (legal limit 70) so at 60mph, big lorries are trying to pass. Now I cruise 70mph at 3000rpm and the car is less noisy, less jumpy, smoother, and more economical. 3.08 may be numerically too low for you in US? Also, I have a 2.56 1st gear so 3.08 works well. If I had the close ratio 2.2 first gear with 3.08, I'd be burning the clutch in 1st and reverse - in effect, my 3.73 2nd gear would be similar to my 3.08 first gear - this can get overlooked. As I said with a 2.56 1st, 3.08 is still good. Yes it's not as punchy but I feel the torque more, hear the engine tone longer in each gear, and still have fun :-)

[Region Warrior]

I'm a "lot of gear with big tires" guy, but don't drive it regularly. Mostly to friends bbq's and such.
They expect...no...demand a show when you leave

[leeklm]

In summary, I think you will be happy with anything from 3.23 to 3.55. My car originally had 3.90 when I bought it, which as you know was terrible on the highway. I ended up with a 3.31 chevy 12bolt and have tried both the 2.56 & 2.20 first gear in my Muncie. I went back to the 2.56, which is a lot easier on the clutch.

I rarely drive faster than 65, and the only time I wish I had something steeper than my 3.31 is the occasional trip to the drag strip. Of course the ultimate drive-ability option is to go with the 5spd OD, but if I wanted that much technology, I would sell my 66 for a 2006!

[indetrucks]

Thanks for all the tips guys. I want to go with either the 3.23 or the 3.55's. I also want to keep the posi and just do the gear swap (not the whole rear end)

Who is the best supplier to buy the gears from? I tried doing a gear search on Summit but it didn't work out very well.
I need to be looking for the 8.2 set-up right?

Am I on the right track with these options?
3.55's
http://www.drivetrainamerica.com/p-2...ntiac-355.aspx
3.36's
http://www.drivetrainamerica.com/p-2...-gear-set.aspx

Summit 3.36's
http://www.summitracing.com/parts/rm...13-1/overview/