The Stovebolt Site Forums The Shop Area Engine Shop Other ring and pinion set than Patricks

I have a 3.55 ring and pinion set from Patrick's on my chevy 52 truck with original transmission and closed torque tube.
It's nice but for freeway driving it's still a bit much rpm at 2900 and 70mph.

Are there any other existing r&p sets from other GM vehicles or current production vendors to bring it down further to around 3.00 or just under, giving about 2400 rpm at 70 mph ?
Both first and second gear of the original transmission would shift a lot better and later this way.


I will put a 261 in a chevy 47 coupe next spring and am thinking about the simplest way to lower rpm on the freeway while keeping the shifter and driveline stock and without having to go with an additional aftermarket overdrive unit or replacing everything entirely.

cant help you much,, I had your same set up in my 52 halfton,,,patricks 3:55, their modified sagnaw four speed shifter.......drove it a lot on the free way,, no problem except the high rpm even in fourth it would be close to 3000 at 65.........

the enclosed petered out so I just went ahead and had a s-10 five speed and blazer 2:73 rear ... I can now got 65 at about 1800 rpm.......a lot less strain on the engine.. I like it real well.. I drove the patricks set up for about 5 yrs,,not bad but I like my new set up better, like to drive it on the hiway.......not much help to you but I do under stand your problem.

You may be able to drop some rpms by running a little taller tires. Looking at the number cruncher I'm getting that you're running about 29 inch diameter tires. Going to a 31 inch diameter will bring your rpm's from 2,900 down to around 2,700,without any other changes. That appears to be about the best you can do without doing some tranny or rear end changing.
Speed

If you go the larger diameter tire route, have the tire shop get the hight and width dimensions first. Just asking for a 31" tire might end up getting you a tire that's too wide. Generally, if you ask for a 31" tire, they'll assume that you want a 31x10.50x15. That's a little too wide for an AD truck, and will rub on the fender. Any good tire shop will have a tire spec book that has the dimensions of the tires as they are mounted on a given width rim. You'll want to stay within 7"-9" to prevent tire rub. This is a lesser peoblem on '55 2nd and later, and the '67-72 can fit some pretty big tires in their fenders, 32x11.5x15 clears nicely on them.

I think CD has a set of 3.38 gears. This along with tall tires would help. The only way to get in the low 3's or 2's as far as I know is to go with an open driveline.

Experimented with various radial tire dimesions on my daily truck over the past decade.
Started out with 32" but found that the stock height around 29" handled best for around town.

I will leave the 3.55 in the truck, but am thinking about the passenger chevy I will make starting this winter.
I want to set it up for freeway driving but don't like the idea of modernizing the entire drive line. Just not my thing.

I know there are many r&p sets out there - maybe there is a good match...?
Or maybe I have a custom set made. Probably cheaper than all the other options I ever read about, including the illusive torque tube overdrive.
I will ask Patrick if he can help. Maybe he can make or assist with making a lower ratio.
The 3.55 or 3.38 sets are nice, but we need something between 2.5-3
I bet there are a few of us who would go that route, if it would be available.

This question has been asked quite often actually and to my memory no-one has ever been able to come up with any gears other than the 3:55 set to fit the old rear. For the new ride (car) I'd think long and hard about an AOD and open rear with 3:50-3:80 R&P. That would be an near perfect setup IMO.

Those 3.38s are for the '55-'62 open diff.

I would be hesitant to run a 261 in a closed driveline vehicle. Those 261s put out a lot more hp and torque than the original 216s. IMO a 261 w/ torque tube is a disaster waiting to happen, and it won't take too long to happen. You have an added advantage of not having to change the lug pattern for a driveline swap. There are a lot more choices for a 5 on 5 or 5 on 4.75 lug pattern. Just my .02

I don't think it would be possible to have a higher gearset made than 3.55's for the '40-'54 rear. If you could compare a stock 4.11 ring gear to one of Patrick's 3.55 ring gears, you will see why. The teeth on the 3.55 are almost cut through the ring gear, while the stock ring gear is thicker and stronger looking. I remember talking to Patrick about this in the early '90's when he was developing the 3.55 gear sets. I think he originally was shooting for something in the 3.36 range, but had to go with the 3.55 due to this ring gear thickness problem.

If you want something between a 2.50 and 3.00 final, an open rear and/or OD trans. might be the way to go.

Ah, thanks for the insights...!
I start to see why most go for a newer drive line.
I did some research a while back and it looks like the M21 tranny is the only one that bolts on directly to the bell housing and I get to keep the tree-shifter.

I thought of the 261 may be a bit much for the small tranny, but haven't thought of the torque tube.
So how did the rodders of the 30s-50s do it?

They used the stronger packard transmissions. The m21 isn't the only transmission that will bolt up. The saginaw 3s and 4s will also bolt as well as some warner t-10s. The m21 is a good transmission, but could be a little bit spendy. It might be hard to make that one shift from the tree properly... most would install a hurst shifter and cut a hole in the floor pan

I might be wrong, but isn't the M21 a 4 speed? I seem to recall that they were used in big block Camaro/Chevelles with the 396 or COPO 427. Also in Corvettes. If you want a 3 speed, you'll want an SM 318/319 or the later SM 326/330, preferably with the Borg-Warner overdrive. If you want a really tough 3 speed, look for the B-W unit that was an option in the 3/4 and 1 ton models.

34 years and still waiting for that disaster?

check out what this guy came up with on his 50 passenger car

http://www.chevytalk.org/threads/showflat.php/Cat/0/Number/1606083/page/0/fpart/1/vc/1/nt/2

I still don't understand how a torque tube would notice any difference between a mild 261 and a 235.
What kind of disaster is bound to happen?
Please ellaborate - never heard or read anything about that before.

I can only go by my personal experience so far:
I have a daily late 235 with duals in and out pushing my trusted original transmission, torque tube and 3.55 rear for the past 11 years and over 100K miles.
I go regularly for hours at 2500-3000 rpm on the freeway without any strain and have been up and down dirt roads and poorly paved mountain passes plenty.
I was always very relieved to have something pretty indestructible under my seat.

I should know all about weaknesses in early drivelines:
The first 50K and 5 years the clutch, transmission, u-joint, oakie bushing and 4.11 gears ALL were in terrible need of replacement.
None of the original parts could be rebuilt, they were so worn out! Still they held up for all these years and miles in that condition, before I could afford to replace them.
Unbelievably TOUGH these early drivelines!
Even far beyond the point of repair, they just kept going reliably. True story.


Thanks for all the upgrade advice and pointing out trannies that will just bolt up to the engine. Sounds like an option many have experience with.

I just like 10s-40s cars and trucks in general and their original technology. It's a lot more than their outside appearance to me.

If I would prefer higher power engines, later trannies, drivelines, suspensions, power steering, disc brakes, etc ... I would simply acquire a later model truck or car ond enjoy it as is.

People have put 292s and GMC 302s in trucks with the torque tube and not had problems with them. I don't think you will have any issues with a 261.

My origial drivetrain has held up just fine to my 261. I've floored it in 1st gear (in an SM420, no less), without breaking anything. In first gear, the SM420 is capable of applying at least 1200 ft-lbs to the driveshaft and I haven't heard of any of them breaking.

Yep, I know guys running sprint cars with 700 horses through a torque tube with no problems. Well, they have problems. It's just that the driveshaft isn't one of them.

Longbox, you're right, the M21 is a 4 speed.

Interesting topic here.

Good Luck.