VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 rear end ratio change

i have a 1940 special deluxe stock. i heard that a fellow had put a truck rear end 3.08 in his car...is this possible? or is he pulling my leg? i would like to go faster than 45mph. the 3.55 change over is very expensive so that avenue is out. tried to find a 1954 power glide rear end near by but they are few and very hard to find. any suggestions. thanks guys... vcca still rocks after all these years!!!!

1940 Chevy passenger cars generally came with 4:11 gears. The 1940 Master 85 models had 3:73 gears. The good news is that 3:73 gears are a direct bolt in for all 1940 passenger cars. I can travel at 60 mph all day long with my 3:73 gears. Occasionally I have been known to drive 65.
I have also seen less 1950-54 Powerglide 3:55 gears available for sale. They are a direct bolt in if you use the carrier.

dtm

There was NO truck that had a 3.08 rear end and torque tube drive.
There is an adaptor you can buy so the ring gear and pinion from a later Power Glide can be fit into a 1940. The 1950-54 PG gears (3.55) or the 1953-54 Stick shift gears (3.70) and any of these "gears" are still arond. Chevk in the street rod circles as they like to rip out the stock drive lines.
I agree with the "other " reply. My '39 sails along happily at 65 MPH with the 3.73 gears.

thanks guys, i thought that my leg was being pulled. i got to catch the swap meet in louisville, ky. this fall. maybe i can locate what i need there...

I have a 37 Master Deluxe with a 4:22 rear end. Is it possible to change it to a 3:73 ratio? or what are my options? Thanks,
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Joe's 37

YES, same deal. You need to find the "rear end" from a 1937-1939 Master (the front leaf spring cars)

My 37's a Master, so I'm assuming it's got the 3.73 rear end.

Now, one would think that the more upscale Master Deluxe would've came with the more high speed rear end. One would think it'd have been just the opposite; the plainer Master would have been developed for people who drove them in places where pulling power would have been more important than high speed.

I often wonder why Chevy did stuff like this...

Well, think about road conditions in 1937. Paved roads? Far and few between. Smooth dirt road? Not likely. Top speed on country road to grammas house? Probably like 40mph if you were a speed demon.

The higher gears used in the "cheaper" model were for more for economy, not speed. This was because Chevrolet offered only one engine in 1937 and the economy car got economy gearing. They described the 4.22 ratio used in the Master Deluxe as a performance ratio. The cars with the 4.11 and 4.22 gears could go up most hills without downshifting. In 1937 good high gear performance between 10 and 60 MPH in high gear was important. They both can cruise all day long at 60 MPH if the engine is in good shape. The 3.73 gears would give about a 2 MPG advantage at that speed.

I converted my '41 from a 4:11 to a 3;73 by installing a 1954 Chev. powerglide rear end. It worked like clockwork thanks to Chevgene Gene Schneider. Gene walked me through the purchase, installation and followup. I can now go 60-65 MPH where I used to strain to get 50 MPH. I found my rear end through a friend that has played with cars for years. I'm sure there are several junk yards and individuals that would have a rear end laying around. I gave $100.00 for mine. When you get ready to convert be sure to contact Gene and he will help you. Even if you think you dont need help it will make it a lot easier and you will do it right the first time. As you know the speedometer will be wrong when you change the ring gear and pinion. I had a local sign man make a decal to put on my speedometer making the needle correct. How did I know what to do on this project. Gene Schneider gave me the percent change of the speedometer and I calculated them and the sign man made the decal. Those computers are great. If any one would like a picture of the installed decal send me your email address.
This forum is worth its weight in gold. There are several members that are "experts" on Chevrolets. I know for fact that Gene is among the top experts.
Good luck JIM JAR41

Well, thanks guys for all the info on the rear end ratio's. It was a busy day today, giving rides, to family members and such. Thanks to this club, and it's members, the old girl has never ran better!
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Thanks Agin, Joe's 37

I am a little confused on all this rear end swapping when it comes to how the axles will interchange. A few years ago I asked if some '39 axles I had would work in my '38 Master. I think I asked the question because I wanted to get rid of them if I couldn't use them. Someone, I believe it was Chev Nut, told me only '38 axles would work in the '38 Master rear end. How do axles come into play on a rear end change? Beamer

In lieu of finding a replacement rear end, can't the ring and pinon gears be replaced? I've seen some on ebay, but they are likely not for the older cars.

http://cgi.ebay.com/ebaymotors/gm-c...torsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Rich

Thanks for the link. This is a complete kit with bearings and gaskets. Looks like a deal.

I also believe that a replacement gear for the speedometer is available so that it will read correctly.

Rich

So that would be $700 for the kit and ring gear and pinion? + the speedometer adaptor....ouch

The original axles are used. When a swap is made the axle banjo housing and axles from your car are retained. Only the torque tube , center housing and internal differential parts are changed.
Remove rear cover, remove axle locks and pull out axles. Unbolt differential housing from axle housing. Drop U joint. Pull housing forward from axle housing - to install reverse operation. Would advise replacing bearings in an unknown unit. This requires setting up the pinion depth and ring gear to pinion clearance.

I should add - while your in there replace the drive shaft bushings with an Oakie bushing.

Gene,

I misread the catalog. In this picture, they showed the ring and pinion along with all the other parts. I thought the $299 was for the complete kit.

http://www.patricksantiquecars.com/ringpinioninstkit.jpg

Yes, that's a chunk of change.

Rich

You guys all make me laugh. These are real people behind some of these outfits. Go ahead and make an offer instead of just accepting the printed price. Do you pay sticker price on your car? Last time your kid asked you for $50, did you just hand it over? Or did you say, "How about $5" Now I am sure they won't come down too far from that, but, I worked them over on the phone, got better prices for stuff I don't plan to buy until next year! Just try and see!

Maybe they will have a half price sale for Christmas.

You would also need some kind of an adaptor as the 1940 and up pinion gear will not couple up to a 1937-39 drive shaft.

With the 3.55, high altitude power loss, and mountain driving you can plan on being in 2nd gear 50% of the time. The other 50% you will be going down hill.

Gene,

Right now, my wife's car is in the shop for hail damage repairs. She is driving my ride and I am driving the '37. So, I have put on several hundered miles this past few days and each time I upshift, I feel like just one more gear and all would be fine. But, the car does fine at 55 mph and that's where I do my "high speed" cruise. While I would like to have the engine going slower, I think that I will just leave well enough alone. It "ain't broke" and that's good.

The power loss at altitude is a factor too. I was recently tempted to drive the car to the top of Mt. Evans. That's about 14,200' on the road. I checked on the internet and found that water will boil at about 183 degrees at that altitude. I don't know what the un pressurized cooling system would do if it were operating at a full boil so I did not try it.

Rich

While climbing mountains the work done by the engine increases thereby increasing the heat to be removed by the radiator. However the atmospheric temperature decreases as you go higher so cooler air in going through the radiator. The third factor is the rate of air movement through the radiator decreases as road speed (also depends +/- on wind direction) decreases thereby reducing the heat transfer. Fourth the circulation rate of coolant is dependent on engine speed. Fifth as you increase engine speed it produces more available horsepower. Sixth as you noted the boiling point of the coolant decreases with an increase in altitude.

The bottom line is that if you take it easy and make sure to keep the rpms up climbing mountains can be done safely in an old Chevy. If it begins to over heat or loose coolant then pull over, keeping the engine running for a few minutes to help dissipate the heat built up in the engine (that will help keep coolant in the system).

If I lived in your area and did most of my driving west of home in the mountains I would also leave well enough alone. Especially if you are conent with 55 MPH.
Believe it or not those old 216's were know for their excellent hill climbing ability. (with a 4.11 or 4.22).
Your car will out preform the other two 1937 low priced cars in high gear and most higher high priced cars. Some cars offered optional mountain ratios like 4.55 and 4.78.
To help with cooling the Master with the 3.73 ratio had a larger and noiser fan and more cooling fins in the radiator.
At best the 1937 and 1938 Chevrolet cars had a marginal cooling system and even offered a heavy duty radiator for better cooling......Even with the set=up you have there again they would not overheat as easily as most cars.
I was to the top of Mount Evans and Pikes Peak with my 1941 Chev with no overheating problesm...that was in 1951.The '39 was up to the top of Pikes Peak , got warm but never overheated. When the going get slow I pop into 2nd geat to keep the RPM's up so the fan sucks more air through the radiator.
How many miles since the ring job and how is the oil consumption?

Just thinking back to my Colorado trips
1951 Pikes Peak and My Evans - 1941 Chev
1953 both - 1953
1956 --- PP 1955
1968 Both - 1968 Impala wagon demonstrator
1976 PP - 1939
Visited Colo in 1985 and 1994 and 2006 but no big mountains
Most exciting - July 3 1976, the Gold Camp Road during snow storm

Gene,

I have over 500 miles on the rebuilt engine and as near as I can tell, I have zero oil consumption. The car starts and runs well. The longest trip I have made is about 40 miles at highway (55 mph) speed with a little stop and go at each end of the trip. That was today.

On a hot day, I do feel that the cooling system is marginal. I have the water jacket cleaned out very well and I have a new water pump and new radiator (nos.) Until I read your message tonight, I did not know that there were different radiators on the master and master deluxe. How can I tell which one that I have?

This evening, I had the engine die when I was about 1/2 mile from home. It died at a red light. I tried to start the car with the starter and it did not seem to want to start. I was on a slight down hill grade and I managed to coast to pick up a little speed and then I popped the clutch and the engine took off again. I wish I knew what caused this and what to do about it. The engine was not hot and it was running just fine right upto the point where I stopped at the light. I drove the car again this evening and all seemed normal again. I did increase the idle speed not long after the rebuild and that was a big help. Any clue as to what is happening?

Rich