Has anyone tried a tall 4th gear

[Stewart A.]

I'm in the process of pulling my T 10 apart and wondered if anyone has ever tried a really tall 4 th gear. I love the 3.70 rear but 4th at 60 mph at 3200 rpm is getting rather tiring. We tend to travel long distances here. I have fooled with changing rear ratios but that's no fun. I was wondering if an overdrive 4th is possible ? Stewy

[Tom L.]

Re: Has anyone tried a tall 4th gear

Don't know if it is possible but my Mustang has a .68:1 5th gear ratio with 3.73's in the rear, about 2200RPM at 65MPH bit is a dog in 5TH. Down shifting means a drop to 3rd (passing by 4th, 1:1). Helps out on fuel economy but high gear is boring!! Have fun!!!

[Stewart A.]

Re: Has anyone tried a tall 4th gear

I thought 3 faster gears and a tall 4th would be ok. Overtaking might be a problem with a tall 4th. I never thought of that and changing down to 3rd might be dangerous. That's why they make a 5 speed ah. Stewy

[Mike M.]

Re: Has anyone tried a tall 4th gear

I'm in the process of pulling my T 10 apart and wondered if anyone has ever tried a really tall 4 th gear. I love the 3.70 rear but 4th at 60 mph at 3200 rpm is getting rather tiring. We tend to travel long distances here. I have fooled with changing rear ratios but that's no fun. I was wondering if an overdrive 4th is possible ? Stewy

with stock tires, a 3.7:1 rear should be running 70 MPH @ 3000 RPM. mike

[Stewart A.]

Re: Has anyone tried a tall 4th gear

Maybe my 50 year old counter is a wee bit out. It's still screaming at 60 mph though. stewy

[Steven B.]

Re: Has anyone tried a tall 4th gear

'easiest way to "change" the effective ratio is to put taller tires on it. what size do you have on it now?

[William C.]

Re: Has anyone tried a tall 4th gear

I've road toured my '62 just swapping a 3.36 rear gear and correcting the speedo drive gear. The T-10 case is not desiged for a overdrive 4th setup, so you would have to go to an aftermarket trans. Used 3.36 "pigs" for a solid axle are relatively easy and inexpensive to use, and it was also a gear used in many 63-67 cars.

[Steven B.]

Re: Has anyone tried a tall 4th gear

I've road toured my '62 just swapping a 3.36 rear gear and correcting the speedo drive gear. The T-10 case is not desiged for a overdrive 4th setup, so you would have to go to an aftermarket trans. Used 3.36 "pigs" for a solid axle are relatively easy and inexpensive to use, and it was also a gear used in many 63-67 cars.

Yep! I picked a set of 3.36's & posi from a junk yard for $35.00 recently.

[Stewart A.]

Re: Has anyone tried a tall 4th gear

If I use a 3.36 what would be the RPM at 60 mph then. My tires are 6.7 x 15 typical white walls. Stewy

[William C.]

Re: Has anyone tried a tall 4th gear

for a quick estimate, figure 25 mph per 1000 engine rpm so 60 is about 2350

[Duke W.]

Re: Has anyone tried a tall 4th gear

If I use a 3.36 what would be the RPM at 60 mph then. My tires are 6.7 x 15 typical white walls. Stewy

Axle ratio times tire revs/mile = revs at 60, and you can linearly proportion from this point.

This is an easy formula to remember.

Corvette OE tires from 1953 to 1982 were 760 (6.70. GR70, 225/70) or 775 revs/mile (7.75, F70, and 255/60)

Duke

[Richard T.]

Re: Has anyone tried a tall 4th gear

Years ago when I was in the military I drove my 340 HP 62 coast to coast a few times and installed a 3:08 for the trips. It ran around 2100 RPM @ 60 and was great on gas.
These rears can be changed out in an hour or less with the only expense being fluid and a fresh gasket. In my teens we would change to 4:56 s to go racing on Friday night and back to 3:70 s on Sunday evening.
If you travel long distances as a rule then the 3:36 or 3:55 is the way to go. Let's face it we don't really beat hell out of these cars very often any more so the deep gears are hardly missed. I built a fresh 3:55 posi for the 62 to replace the 4:11 s and someday I'll change it out. Rich

[Cecil L.]

Re: Has anyone tried a tall 4th gear

You could also do a muncie overdrive conversion with a new gearset and save your T-10.

[Ted S.]

Re: Has anyone tried a tall 4th gear

Also if you go to 3:36 you could change the T10 set to a wide ratio set verses the original close ratio. That way you'd still have some lower end for the "go fast".

[John S.]

Re: Has anyone tried a tall 4th gear

Stewy,

William Culpper's est is pretty close. I can tell you my 67 with the 3:36 gears turns right at 2700 RPM on the tach at 70 mph. I do not know how accurate my tach is, but according to my gps, I am only 1 mph off at 70 (actually 69). My car is only 300 hp (I have never ridden in a big block vette) and I can tell you even with the 3:36 gear it is still a kick to drive.

John Seeley
67 black/teal coupe
327/300 hp 3 speed