lower gearing choices

[bbbbuick]

Hi all,

I've been debating whether to go OD trans or lower rear gear set to get better (lower) rpms on highway for quite some time, I'm currently running 3.55s. I've settled on rear end change as the method, mostly due to cost, but wonder how low to go. From what I've read from the forum it seems 3.08 or 2.93 is what would have come stock. JDRace is out of those but does have a set of 2.73s. Anyone running that low a set that could comment on drivablility? Thanks.

Elvin

[gssizzler]

Are you running a nailhead with the stock st 300!? I know on my buddies skylark which is a 300 st 300 combo with a set of 2.78’s posi ,it is running 500-700 rpm less at highway speed! His car gets the best mileage and rolls down the road the best at 60-65!? If this helps!? So not fast off the line but super great cruising gear and not beating things up! Unfortunately they don’t make the 2.56 - 3.08 gears new that I know of and no posi units new under 2.93!? I believe so you have to find good used! I had to find a good set of 3.08’s for my convertible! Was a challenge! Put a want add up here and on V8!

[WkillGS]

To put 2.78 gears into your car you will need a new carrier, the 3.55 carrier will not work with the 2.78's.
Does Jim @ JDRace have everything?

There are RPM/gear/speed calculators readily available to help you determine what the effect would be:
https://www.randysworldwide.com/calculators/rpm

Going from a 3.55 to a 2.78 would change your rpm about 600 rpm, or give you 15mph more at the same engine rpm.

Adding a GearVendors overdrive will give a similar result. The 0.78 OD ratio would make your 3.55 like a 2.77 when engaged. Cost is about $2600 for the setup:
https://www.gearvendors.com/hrgm3s.html

I have a 2.78 in my '66 Special with the 300 engine. I opted to put a Richmond 5 speed in it. I love it!

[Jim]

Hi,had  overdrive in our last three cars really miss running 70 at 2,300 rpm .jim

[dsags]

Adding a GearVendors overdrive will give a similar result. The 0.78 OD ratio would make your 3.55 like a 2.77 when engaged. Cost is about $2600 for the setup:
https://www.gearvendors.com/hrgm3s.html

I have a 2.78 in my '66 Special with the 300 engine. I opted to put a Richmond 5 speed in it. I love it!

Explored a gearvendors unit for a 65 Skylark. The owner said that the tunnel would have to be beat on quite a bit to make it fit.

Dan

[Lou Perfetto]

Hi,
Don't take those 3:55's out. That is a fun gear. Our cars have to make a statement, your not going to do that with 2:73's at a red light. I know we all drive our cars different. Gear Vendors overdrive are too heavy in my opinion. I would keep your gears and run a 2004r behind the nailhead. I found this on V8buick, hope this helps.

Bendtsens Adapter, $675:
http://transmissionadapters.com/Nailhead_install.htm

https://www.nailheadbuick.com/transmission-options
 
Keep frying them.....

Lou     

[TrunkMonkey]

...
Explored a gearvendors unit for a 65 Skylark. The owner said that the tunnel would have to be beat on quite a bit to make it fit.

Dan

I had GV in my 64 behind nailhead and T10. Only had to put two "dimples" in the tunnel between the bucket seats.

(think large ball peen/golf ball) maybe to obtain about 1/2 in the 10 and 2 oclock position at the top of the tunnel).

Certainly not "beating quite a bit". I actually used a 21 oz ball peen and a small sledge to make the dimples.

FWIW.

And, yeah, 3.55 rear gears, the car pulled great when splitting 3rd around town, or spitting 4th on highway for passing.