Swapping Rear Ends ???

[FLYER15015]

No I didn't spin out on wet pavement or anything like that.

I've read with interest about changing the rear axle ratio, and slowing down the revs per mile.

So as a fall/winter project I would like to get started searching for the required components.

Question is how to do this on a 1940 series 90 Buick. Pretty long wheelbase here.

So far the torque tube is fine and we have new brakes, so is it possible to save the unit and transfer a new (1953 I've heard) ring ("crown" for Grant and Danny) gear and pinion with the lower ratio. Can I swap out the 3rd member, or do I have to swap the whole tube/ axle assembly, and if so how do I maintain the same wheel base ? Won't the torque tubes be a different length ? Or won't the torque balls/ spline be different ? Lots of research to do here.

I'm not afraid of tearing the whole unit apart and at the same time do all the bearings and seals.

Guess I'm looking for someone with a series 80-90 that has travelled this road to chime in here, before I go buying a bunch of parts that won't fit.

Mike in Colorado

:confused::confused::confused:

[1939_Buick]

The common information is about series 40 & 60. Using 1940 ~ 1954 is bolt in up to a point if you use the original torque tube

The 37-38 prewar guys cut & weld the torques tubes to fit 1940~1954 high speed diff's

Good information in 1937 and 1938 Buicks.com (but I will send you an email)

Your rear axle housing is not the same as series 40 & 60 The series 80 & 90 are a new game !

Edited June 26, 2013 by 1939_buick (see edit history)

[Guest Grant Magrath]

You gots the pioneering spirit Mike! And thanks for considering us folk down under when reffering to crown wheels, boots, bushes and bonnets. And may your grease nipple remain unblocked!

Cheers

Grant

[CHAD THOMAS]

I have a 41 series 90 rear end if you need/ want a spare before tackling this project.

[1939_Buick]

This is thread on H.A.M.B is very good (with photos) Technical For you Buick Torque tube guys that’s want to change gear ratio - THE H.A.M.B.

Another: Technical 1940s 1950s Buick ring and pinion interchange help? - THE H.A.M.B.

This may be of interest http://www.teambuick.com/forums/showthread.php?20920-rear-gear-swap

There are also threads here on AACA.org

Edited June 30, 2013 by 1939_buick (see edit history)

[Ben Bruce aka First Born]

Mike, I have done that in my '50. You will be thrilled. After the work is done, that is. I am not certain, but believe the gears from all series are the same. You will want at least a 3.4:1 [actually is a 3.36, if that matters]. Mine had a 4.1 and going to the 3.4 dropped 650 rpm in 3rd gear.They exchange through '55.

PM sent

Ben

[RiKi5156B]

I put a 50 special 3.6 in my 40 special housing.Bolted right in no mods. Different years had the spring pads either on top the housing or behind it. Naturally that would not work so check it before you buy.

[Guest BigDogDaddy]

Mike, I'm thinking more of how this will affect your around town driving. By going to a lower gear ratio, you are going to loose some low end grunt which is where you do most of your driving. With your car being a 90 Series, and quite a bit heavier than my 80 Series, your poor engine is going to have to work harder around town. I've often read the threads and listened to the stories of guys want to swap their gears for better highway driving. I've never even considered this since my car will easily do 70 mph all day long and not even break a sweat. Most of the people doing this swap are looking to make their car better able to achieve highway speeds. We've already got that. I don't do 70 mph often. I usually keep it around 60 - 65. I have no idea what rpms the motor is turning. But it sure is smooth. The Limiteds also have taller tires than the other Series, which helps offset the higher gear ratio. Unless you plan on running the Cannonball with it, I'd leave the gears alone.

A friend of mine did a complete rearend swap in his 1931 Essex Touring sedan because the car is comfortable only cruising around 45 - 50 mph. After a lot of work, he only gained a slight change in rpm and a few mph. The car still doesn't want to cruise at 55 mph. So he feels he wasted his time. By the way, he checked his speed with a GPS unit, and didn't rely on the factory speedometer. I check my speed the same way.

Phil

[Dwight Romberger]

I am not a mechanical engineer (which is probably a real blessing to the automotive world), but I am surprised no one offers a small universal overdrive gearbox one can install between the trans and torque tube or drive shaft. It would not have to have the complicated connect/disconnect feature of the currently available $2000+ overdrive units. It would operate all the time. One would modify the length of their torque tube or drive shaft to accommodate the length of the unit. The car could be put back to original by removing the unit and reinstalling an OEM torque tube or driveshaft. This condition of high low end torque and low top speed bothers owners of drivers from Model T's to Packards. The product would seem to have a willing market.

Edited June 27, 2013 by Dwight Romberger
I can't spell suprized (see edit history)

[CHAD THOMAS]

I am not a mechancal engineer (which is probably a real blessing to the automotive world), but I am surprised no one offers a small universal overdrive gearbox one can install between the trans and torque tube or drive shaft. It would not have to have the complicated connect/disconnect feature of the currently available $2000+ overdrive units. It would operate all the time. One would modify the length of their torque tube or drive shaft to accommodate the length of the unit. The car could be put back to original by removing the unit and reinstalling an OEM torque tube or driveshaft. This condition of high low end torque and low top speed bothers owners of drivers from Model T's to Packards. The product would seem to have a willing market.

This has never occurred to me. I spent a lot of time thinking about modifying an OD unit to fit existing transmission, but what is wrong with a small box with and input and out put shaft and a small gear set inside to achieve the OD? cannot be that hard to do.........

[Dwight Romberger]

Chad,

Should we start taking orders?

Dwight

[Ben Bruce aka First Born]

R:E Phil's remarks in post #8, yes one loses a LITTLE around town. But only at real low speed in 3rd gear. If mine gets below 10 mph, I may have to shift to 2nd. Anything above that seems to be no problem. At 12 mph the engine rpm is at about 500. Just at idle.

Mike, it looks like I will not make South Bend, but if you do, and care to swing by, do so. Drive mine and judge for your self. I find I like the lower rpm even in town. Quieter..

Contact me about swapping. I will talk your head off!

I have a GPS speedometer and a tach setting between the steering wheel and dash.So numbers I quote should be accurate.

Ben

[jvelde]

I knew my speedometer was wrong, so I downloaded the GPS Speed mobile app on my phone to check it. Appears the speedometer is showing 45 mph when I am really going 40 by GPS. Haven't tried going faster yet to see if it gets further apart at greater speed - suspect it does though. Will be driving to North Texas Buick Club meeting on Saturday, so should have a chance to get going faster on the toll road.

[Matt Harwood]

I'll start by saying that I don't know if 1940s are the same as '41s, but I'm fairly certain that in '41 the Limited had an entirely different rear end than the other cars and I don't believe the rings and pinions (crowns and pinions?) are interchangeable with the other series, particularly post-war. The Limiteds had a really BIG pumpkin as opposed to a merely large one on the Roadmaster/Century.

That said, I have retrofitted an overdrive to my 1929 Cadillac which uses a torque tube. It actually fits in the center of the tube and if you do a search on this board, I'm sure you'll find all the details I wrote (I'm on my phone else I'd do it). It is a Borg-Warner unit from a '50s Ford, I believe, and offers a 30% overdrive without affecting around-town performance.

I also have a 1932 Buick 90 series that I have driven a lot recently, and it has a set of "high speed" gears in it that appear to be 15-17% lower than stock. 45 MPH on the speedo is about 55 MPH road speed, and that's where it likes to cruise. It does not seem to affect around-town driveability at all, and it still pulls cleanly from about 8 MPH on the speedo and in normal driving, I'm still in 3rd by 20 MPH. The reduction in cruise RPM isn't as dramatic as with the overdrive (the Cadillac does 2000 RPM at 60 MPH), but it's definitely not a handicap for regular driving.

The overdrive is a PITA to install, but I'm sold on them and am considering putting one in the '41 Century before I bolt it all back together. There's also a Mitchell overdrive that's popular with Model As that is designed to fit in a torque tube, and the guys at Gear Vendors will engineer you an overdrive unit for your application complete with tube halves and driveshafts so it's a bolt-in. It'll be expensive, since you're footing the bill for the R&D, but that is the absolute best overdrive unit, bar none. Overkill for an old car, but it'll never break and I like their ON/OFF switch actuation rather than the solenoids, free-wheeling, and hope that powers the Borg-Warner.

Hope this helps!