PB----advise

[broker-len]

this is for a friend with no access to this forum----PB roadster---,,as far as I know stock    for some reason feels the motor is over reving at 40 mph  though has power   wants to change the gears in the rear end      assuming his rear is as stock   4.33 to one    he tells me he has found two possible set ups   3.54 and 3.46     from 40s chryslers     is there any one who has attempted this swap ??    out come  ??   did it achieve the desired results ??    has any one just put on an overdrive ?   were you happy with it ??  is it worth the work ???      I thank you in advance for your comments  BR   bobnroman@yahoo.com

[32plywood]

some of the old timers put a later year ring and pinion in the original rear end but not sure how it was done and the last person that talked about that is gone now.

 

Paul Curtis put a s10 t-5 in his PA convertible and he built adapter parts for a while.

 

they also have mated a late 40 to early 50 overdrive rear gear set to a stock PA -PB trans but I do not know anybody that still knows how to do that anymore ---- a while back one of the conversion transmossions sold on Ebay. 

 

this could be a good question to the plymouth club groupe --Allan

Edited August 11, 2022 by 32plywood (see edit history)

[broker-len]

have a phone number and E mail for paul     both are no good     any one know how to contact him would like to fine out more about the job--------------------     BR

[F&J]

On 8/10/2022 at 10:36 PM, 32plywood said:

some of the old timers put a later year ring and pinion in the original rear end but not sure how it was done

Back in the late 80s at Hershey, a group of Ohio PB owners shared a few swap spaces.  They all said they used a entire center section gear chuck from a very late 40s or very early 50s Plymouth rear end, I think they said to find one with a 3;90 ratio.

 

So I found a complete 3;90 rear end from a 1950 Plymouth, and the gear carrier chuck did have the same splines as the 32 axle shafts, the depth of the centerline for the axle shafts were the same.  But, the 1950 chuck did not fit into the opening in the 32 main housing, and had wrong bolt pattern.

 

Then I saw them again the next year.  They forgot to say that they had to cut the bolting flanges off of both rear axle housings, then weld the later flange into the 32 housing.  Too much fussy work for me back then, so I sold the 32 conv. after a few years as i hated driving it.  Most cheaper cars were geared for 40-45 MPH roads back then.   Mine just couldn't stay up to the needed MPH on secondary State Routes without over-revving.  I had to run in the gutter to let modern cars pass. 

 

My experiences with any early 30s transmission First and Reverse gear ratios is that if you go to a numerically lower number rear end ratio than a 3;90, then First and Reverse are then geared up too high. Car goes too fast in reverse, and First and Reverse you have to ride the clutch more to get it moving. (so I am sure a 3;50 ratio would not work well)

 

The 5 speed might be a better choice, but you'd need good machining skills to make it fit the PB engine. Also some 5 speeds have the shifter coming up through the floor too far back.

 

. 

[broker-len]

F&J    thank you so much for the info     I have sent it to my friend with the PB

[F&J]

1 hour ago, broker-len said:

F&J    thank you so much for the info     I have sent it to my friend with the PB

I forgot one more very important thing about trying to use a ratio around 3;50 with these lower power engines in the 30s...  If he lives in the flatlands of Kansas, etc, he might be OK except for riding the clutch to get moving.... but, if he has hills, even moderate somewhat longish hills, he will run out of power and road speed and be forced to downshift to 2nd gear!   Then he'd be screaming at 25-30mph.

 

That would be a huge disappointment after doing all the work.   

 

A friend has a 47 dodge pickup with a newer 3.54 gear carrier which is a very common popular bolt-in swap for those trucks, but the bigger engine has enough power and torque to not slow down on hills.   So, if your friend knew about those trucks doing fine with that gear, he might assume that the 32PB should do fairly good too.  It just won't, on many hills.

 

A short hill you could speed up first with 3;50 gears, but a longer hill you just keep losing speed until you must downshift.

[31plymouth]

You have a PA  broker -len.  Do you think it revs too high at 40MPH?.  I've been driving my PA for 50 years and never thought it was reving too high at 40 .  Does he do a lot of long trips?  Does he want to go 55MPH?.   Seems like a lot of work to change anything in the rear end .

 

 

 

 

 

[nzcarnerd]

He said he 'feels' it is over revving. Compared with what? Old cars are much noisier and busier sounding that even car from a few years alter. Has he actually put a tachometer on the engine to see what revs it is pulling.

 

Our all-stock and mostly original 1929 Plymouth has the stock gears in it. I guess compared with the PB it is very slightly taller geared due to its 20 inch wheels but even so at 55 mph it is only doing 2700 rpm - which is close to peak power for that model. It is certainly noisy - and of course in that era cars didn't have any thing like the sound and vibration proofing of later years - but not so much that you can't converse with the front seat passenger.

[Grimy]

1 hour ago, nzcarnerd said:

He said he 'feels' it is over revving. Compared with what? Old cars are much noisier and busier sounding that even car from a few years alter. Has he actually put a tachometer on the engine to see what revs it is pulling.

 

Our all-stock and mostly original 1929 Plymouth has the stock gears in it. I guess compared with the PB it is very slightly taller geared due to its 20 inch wheels but even so at 55 mph it is only doing 2700 rpm - which is close to peak power for that model. It is certainly noisy - and of course in that era cars didn't have any thing like the sound and vibration proofing of later years - but not so much that you can't converse with the front seat passenger.

As I said in another thread, my rule of thumb for cruising speed is NTE (Not To Exceed) 70% of the published redline *or* (if no redline published) the rpm at which max horsepower is calculated.  I'm talking about cruising speed; occasionally one may need to exceed that speed to pass or to get a run at a hill.

[Canadian PB Kid]

Here's page three from the 1932 Plymouth PB sales brochure indicating that the PB is capable of doing 70MPH+ and almost 50MPH in second gear with factory gearing. One would think that the factory engineers would've tested the engine to see just how long and well it held together at the RPMs required to achieve this speed and would not have advised to promote such speeds (RPMs) if it didn't stay together?... I certainly wouldn't want to drive one at 70MPH but it would be nice to know the max RPMs that Walter was promoting. 

 

Can anyone figure out what RPM the PB engine would be turning at 70MPH with factory 18" wheels and the stock driveline?... math isn't my thing...

 

Hope this helps,

 

Dave

 

STAY SAFE!

[ply33]

I have an RPM calculator on my page about how fast to drive.

[nzcarnerd]

1 hour ago, Canadian PB Kid said:

Here's page three from the 1932 Plymouth PB sales brochure indicating that the PB is capable of doing 70MPH+ and almost 50MPH in second gear with factory gearing. One would think that the factory engineers would've tested the engine to see just how long and well it held together at the RPMs required to achieve this speed and would not have advised to promote such speeds (RPMs) if it didn't stay together?... I certainly wouldn't want to drive one at 70MPH but it would be nice to know the max RPMs that Walter was promoting. 

 

Can anyone figure out what RPM the PB engine would be turning at 70MPH with factory 18" wheels and the stock driveline?... math isn't my thing...

 

Hope this helps,

 

Dave

 

STAY SAFE!

The Standard Catalog quotes peak power for the PB at 3400 rpm. Assuming a tyre diameter of 28.5", (18 + 5.25x2) 70 mph is just over 3500 rpm.

 

Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio (purperformance.com)

[Grimy]

3 hours ago, Canadian PB Kid said:

Here's page three from the 1932 Plymouth PB sales brochure indicating that the PB is capable of doing 70MPH+ and almost 50MPH in second gear with factory gearing. One would think that the factory engineers would've tested the engine to see just how long and well it held together at the RPMs required to achieve this speed and would not have advised to promote such speeds (RPMs) if it didn't stay together?... I certainly wouldn't want to drive one at 70MPH but it would be nice to know the max RPMs that Walter was promoting. 

 

Can anyone figure out what RPM the PB engine would be turning at 70MPH with factory 18" wheels and the stock driveline?... math isn't my thing...

 

Hope this helps,

 

Dave

Aren't we talking about sustained (cruising) speed here?  I for one don't think the engineers were talking about that.

[Bloo]

Was it the engineers talking or the sales dept? There weren't too may 70mph cars around in 1932. Some makers might put their car in some race with some tall gears and set a record, and then put lower gears in the ones they sold the customers because the true test of a good car was how well it pulled hills in high gear. Nobody wanted to shift, and maybe with good reason before synchromesh came along.

 

Chrysler, for what it's worth, was an engineering oriented company, and probably made it tougher to hurt the engine than some of the others. In fact, in later years they "ran in" their flathead sixes in a process that probably would have killed some of their competition's engines. 1932 is pretty early though. It wasn't even possible to drive fast in most places, and the speed limits were low. You might be able to brag down at the bar that it would do 70mph, and maybe it would, but there would most likely not be any way to test it, and even if there was, you couldn't sustain it.

 

In about 1940 the Pennsylvania Turnpike opened, a modern highway with no speed limit. The sheer volume of blown engines that resulted is legendary. I think @Grimy's rule of thumb is a good one.

 

Edited August 26, 2022 by Bloo (see edit history)

[F&J]

All of these primitive cars and trucks with different engines, different ratios, all have their own sweet spot where they feel great.

 

I was chastised here long ago by another PA/PB owner when I told of my PB not being able to maintain required road speed on my State Secondary roads.  They miss the point about a cars' sweet spot. Sure, you can go faster with the PB but it vibrates badly. Who would find a badly vibrating car as being "fun" or a nice pleasure ride?  Don't give the same reply as I was given then about "no, my PA/PB does not vibrate"  

 

The factory tried to tame the vibrations with the sales gimmick of floating power diagonal mount system with the quarter elliptic leaf spring keeping the motor from flipping over.  They knew it vibrated, period.

 

Sweet spot:  Do you want to run any mechanical object, engine, grinders, tools, at it's maximum vibration speed?  You think that will be OK?  That you won't be causing stress cracks on certain parts of the car?  Take apart any Model A with high mileage, there are cracks everywhere. Remember seeing those aftermarket roller things to keep door glass from rattling at certain Rpms? 

 

There are no early stock prewars on my roads for almost a decade now.  I suspect it's due to the cars not being able to run in their sweet spot, because that sweet spot is too slow for todays world.  Countless threads on AACA about people with all brands of cars wanting to gear the car up.  There is a reason for that. Many cars only need re-gearing for 5-10 more MPH to not vibrate on their desired secondary roads.

[broker-len]

I am so happy I started  this thread      I have a 32 PA    and with the comments from other owners I feel I know more about my car and am clearer about performance expectations      my car is happy at 40 to 43    any more it is not enjoyable      I think I need to balance the wheels which may improve ride a bit     thank you all