‘38 Chrysler Royal Overdrive Review

[keithb7]

Today I finally drove my ‘38 Royal on the hiway. A trip of about 55 miles one way. There was a car event in my area. Finally we are seeing some resemblance of pre-pandemic life. I wanted to go to the car event. It was also a great excuse to test my car outside city limits. 
 

Up to today, I had briefly engaged the stock OD to test it. It seemed to work just fine. Today I finally got some considerable time on a divided hiway, OD engaged. 

I drove a mountain pass. Plenty of driving up and down hills. The Royal seems most comfortable to me at about 55 mph. It will go faster. I had it up to 62. The OD engaged and above 60, she’s not got much power left to overcome wind resistance.  Perhaps I should try 60+ without OD. Then the engine revs are a bit higher. Maybe the engine is able to produce a little more torque? 
 

Although for me, I have little desire to drive at 60+ mph. I lean more toward the conservative type. Safety is a major factor for me. Stock tires are pretty narrow. Not a lot of rubber on the road. I like the driving experience. Not speed. 
 

The car handled fine. No shimmy. No wobble. Steering true. It drove straight and had good road feel. I felt really planted and secure up to 60 mph. I felt I could easily cruise all day, without tiring at 55 mph. 
 

Overall, the OD experience was very positive. Lower RPM’s, less buzzy. Fuel conserving I suspect. Climbing long hills on the hi-way she lost some speed. To be expected. 

 

 The faster you go more power is needed to overcome wind resistance. Diminishing returns so to speak. So with a later 30’s flathead you can only expect so much. 

 

I got to thinking about cars and driving in 1938. Owing this Chrysler and cruising at 60 mph, I suspect you’d have been in a class above the majority of car owners. 60 mph in 1938 on public roads was pretty serious business I’d think. 

I am pretty-well convinced that my Chrysler would benefit from a 4.11 rear end. Based on where I live and drive, the hilly terrain, I think it would be better for me. From memory, I think my car currently has about a 3.9 to 4.0 gear set in it now. I’ve not opened it up to confirm. I’ll keep my eye out for a 4.11 assembly. 
 

A few pics from today. 

 

 

 

Edited July 25, 2021 by keithb7

[knuckleharley]

I LOVE that dashboard and the instrument clusters!

 

The very first car I bought was a 1938 Chyrsler Royale 4dr sedan. I was 14,and paid 20 bucks for it from the nephew of the original owner. Once we got a couple of valves unstuck,it ran whisper quiet.

 

I don't remember that dashboard,though. Being a one-owner car bought new by a woman,it seems unlikely it was painted over.

 

Can anyone explain this?

Edited July 25, 2021 by knuckleharley

[Daniel Jones]

Keith, I watched your overdrive video and have a quick question.  When your overdrive engages, do you feel it or does it engage smoothly?  I was expecting a bit of a clunk but mine seems to engage very smoothly.  Oddly, mine seems to engage overdrive when the knob is pulled out, not pushed in.  I don't have a tachometer in the car but, with the knob in, RPM seems higher when on the highway and I feel more engine braking.  With the knob out, I don't feel the overdrive kick in but I do notice the car coasts more easily and the engine RPM seems lower.  What I do notice when the overdrive is engaged is that, if I get off and back on the throttle quickly, there will be a bit of a mechanical lag.  Does your overdrive do that?  Also, while the car was in motion (well above 35 MPH), I depressed the clutch and tried to push the knob in but it didn't want to move.  When I attempted to force it, I heard a bit of gear clashing and quickly backed off.  The owner's manual states that "pulling this button out to the limit of its causes the overdrive unit to be inoperative.  Do not pull this button out when going more than 35 MPH.  However it may be pushed in at any speed while the clutch is disengaged."  I need to get back under the car and see if maybe the control lever was flipped so that it's 180 degrees out from where it would have been originally.

[keithb7]

When I engage OD I push the cable knob in. I never do this while the car is in motion. I am completely stopped. Push the cable knob down. Then drive away, shift normally.  You need to reach about 25 mph or faster. You can be in second or 3rd gear. Let your foot off the throttle. Do not put the car in neutral or push in the clutch. While briefly coasting, the OD will now automatically engage. It will feel like you just shifted into another gear. No big clunk, but I can fee it. Then drive away as normal. OD will stay engaged until you slow down below 25 mph.  The OD gear is engaged automatically by centrifugal forces on the drivetrain. It is set to occur at about 25 mph or so. 
 

Do not attempt to pull the knob to disengage OD while moving. Again, pull over and stop. Or at a traffic light. Then pull the cable knob to disengage OD. 
 

While OD cable knob is pushed down, in theory you could still prevent it from being allowed to engage when you are above 25 mph. Just never let your foot off the gas. Hard to drive like this though. 
 

 

Edited September 11 by keithb7

[Doug&Deb]

Keith if I’m not mistaken I believe od equipped cars had a 4.11 rear.

[keithb7]

You could be right @Doug&Deb I have not had my Chrysler rear end apart. 
 

Yet even with my Chrysler OD off, my ‘38 Plymouth coupe climbs the hill home faster. It has 4.11 gears. It has a fresh 237 engine. My Chrysler has a healthy 251 engine. 

 

My research tells me the sedans got 4.11  and the coupes got 3.9x gears. It feels like it when I compare the two cars.  You could be right though. Perhaps my Sedan is lighter than my coupe. Perhaps my sedan has different gear ratios in the tranny. 

[Daniel Jones]

Keith, my 1938 Chrysler Shop Manual states the final drive ratios for C18 Royals were:
   4.3:1 with overdrive (all)
   4.1:1 without overdrive (sedans)
   3.9:1 without overdrive (coupes)
   
For the 1938 C19 Imperial and C20 Imperial Custom, the ratios were:
   4.3:1 C19 with overdrive  
   3.91:1 C19 without overdrive
   4.55:1 C20 with standard overdrive

 

Oddly the T86 with R6 overdrive lubricant capacity is different in each application.  The C18 is 3 1/4 pints, the C19 is 4 1/2 pints and the C20 is 6 1/4 pints.  I can verify my C19 needed over 4 pints after I drained it. 

[keithb7]

Your info is believable. Yet the performance of my Royal with OD vs my 4.11 Plymouth has me questioning what is going on with my Royal. Perhaps my Royal got a custom swapped gear set. It Sure feels like 3.9x-ish to me.  One day I’ll have it open and can confirm. 
 

I’d say, my Chyrsler definitely does not feel like 4.3:1.  Definitely not.  Maybe its different tire sizes betwen my two cars. I never have never checked. 

Edited September 14 by keithb7

[Sniper]

14 hours ago, keithb7 said:

Maybe its different tire sizes betwen my two cars.

 

That may very well have an effect on rear gear ratio choice by the factory.  Shorter tire is going to have more of an effective gear ratio than a taller tire, all other things the same.  So maybe the factory chose the gears to take that into account?  Some days it feels like we are archeologists, lol.

 

 

I wonder what the effective gear ratios are?