Ring and Pinion PITA...

[James_Douglas]

I really do not want to have to replace the rear end in the big Desoto with something else. But, the ring and pinion is becoming a PITA.

The DeSoto Suburbans share the large chassis of the Big Chrysler 8. If it only had the eight!

 

The issue is that I have called and called everyone that has parts and nobody has a set of NOS ring and pinion gears. My 4.11 set is way to pitted to reuse. I have a NOS set of 4.55 gears. But this may be way too much. Keep in mind that with the 3.91 gears in the car right now it is straining to make it up a big hill or mountain. I almost have to drop from their gear (on-OD) to Second. For those of you that know the SF Bay Area, on the way home to SF I am in 3rd non-OD at full throttle to make it up Waldo Grade to the bridge.

 

Attached is an screen shot of an excel spreadsheet of my trans and the the gears 3.91, 4.11 and 4.55. Until I pull the unit I have no idea as to what the shape of the 3.91 is, but it is howling like a sick dog.  It could be just a bad bearing, but I doubt it.

 

I would like peoples thoughts after looking at my spreadsheet as to QUALITY of driving with the NOS 4.55 gears in a car as big and heavy as the Suburban with the overdrive. I added a line for second gear overdrive for city driving at 35. I am thinking it may be a little much as the OD governor does not kick in now until about 25 MPH.

 

Thanks, James

[Bryan]

I changed the rear end of my 92 Dodge Dakota from a 3.2 to a 3.9 ratio.  It has overdrive.. seemed to kick it up from 1800 at 55-60 to 2200 (from what I remember).  If you have the 4.55 and with the hills I'd go with that.   Not scientific, just a gut feeling.  Especially with your comment about full throttle to make the hill.   Maybe you can't cruise at 70-75 anymore, but 60-65 won't be that much change.    Have you overhauled a Dodge rear before or are you paying to do it?

[Sniper]

Can't help on your question, but have you considered a shorter tire with 3.91 gears?  I don't know if you can find a NOS/good used 3.91 gear set though.  I calculate a 3.91 gear set with 27.1" tall tires gives you 2375 at 70 in 3rdOD.

[James_Douglas]

Shorter tires means wider tires...without power steering here in SF parking is PITA with anything wider...

 

It looks like Desoto started to use 3.91 in these cars and quickly switched about six months into production to 4.11...

 

I may just build a 4.55 since I have all the stuff to do so and see how it feels.

 

The other option is to have a custom set made but that is in the $3K to $4K range!

 

I do think that a 4.0 to 1 ratio would be perfect for this car with its weight to power ratio. But they never made one. 

 

I know the Hudson's of the 1940's used a 4.55 in their cars that they shipped from the factory with BW-OD.

 

James

[Go Fleiter]

I´m not sure if I understand You perfectly.

If it is the deactivation speed of the OD,

I can switch its´s OD- relais off by an extra toggle switch (see pic 2).

I´ won´t miss this, I even use the hand switch instead of the original kick-down layout, which seemed to brutal to me.

 

As I didn´t know how OD works, I had 3 LED controls to see what it is doing. The rpm meter is for the same reason.

After I had understood the system, I liked the provisorial panel and let it as it was.

[Adam H P15 D30]

You pull the Waldo Grade at 70?  Impressive

[James_Douglas]

On 10/4/2021 at 9:22 AM, Adam H P15 D30 said:

You pull the Waldo Grade at 70?  Impressive

Usually around 55 to 60 and that is it on Waldo...

 

Today went from bad to worse on the rearend front...

 

Turns out that the ring gear carrier's are different. That is the unit that the ring gear bolts to. For 3.36 and 3.54 it uses one part number while the 3.73, 3.91, and 4.11 use another. So, my "spare" which is a 3.36 does me no good. I just blasted and cleaned my old 4.11 and has a crack in it!

 

So now I will have to pull the 3.91 out of the car that is making noise and that MY daily driver.  The old 4.11 case is now junk.

 

When I put them down next to each other the mounting flanges for the ring gears are in different positions. When I measured the 3.36 ring gear and then the 4.11 ring gear for overall thickness one can see why they use a different case. They are not even close to the same thickness.

 

So much darn fun. I need a drink.

 

James

[DJ194950]

Sure that it is a crack and not just a a line in the casting?  Magnaflux ? .  Does the other side show the same crack?

 

DJ

[Tooljunkie]

That crack is probably factory…

[Los_Control]

There is many cracks from original casting that simply does not matter. Dodge magnum 360 heads in the ports is a common example.

Old Ford Flathead V8's had many factory cracks from original casting.

The list goes on, you need to figure out if it is a actual crack from stress or if it was created from birth.

 

Your crack would either be from birth and 70 years old and never a issue ... or someone put it under high stress and broke it in the last few decades ... Whats your opinion?

 

[Bryan]

When I was overhauling my 92 Dakota rear end thought I had a crack in the casing between rear pinion bearing and side, but it never leaked or showed it was flexing.  Bigger problem was the carrier races spinning in the housing.   What rear end do you have, a 8.75?   Spline count on pinion and side gears?   There are used carriers and aftermarket ones all over for 8.75. The only thing I had to watch for my 8.25 was spline count.

[James_Douglas]

Its hard to see in the photo, but in person it is clear it is a crack. This diff is the one where a ring gear bolt came out and part of it got into the groove and was hammered between the ring and pinion. It mad quite a thump thump going down the road. I was surprised that the ring and pinion looked fine when I took it apart apart from the decades of pitting from sitting at some point. I now know that the it took more of a hit than I thought...

[9 foot box]

   Desert Valley Auto Parts, Casa Grande,AZ, has a fair inventory of Desoto and Chrysler cars, online.

[bigdaisy19k]

Wildcat Mopars in Oregon?

[wayfarer]

...and the reason for not looking at a 'newer, axle assembly? Plenty of variations to consider.

[Los_Control]

On 10/9/2021 at 9:11 AM, James_Douglas said:

Its hard to see in the photo, but in person it is clear it is a crack. This diff is the one where a ring gear bolt came out and part of it got into the groove and was hammered between the ring and pinion. It mad quite a thump thump going down the road. I was surprised that the ring and pinion looked fine when I took it apart apart from the decades of pitting from sitting at some point. I now know that the it took more of a hit than I thought...

I only have a opinion and not useful facts.

I really appreciate your efforts to restore the vehicle and keep it stock.

Whats your plan for the vehicle once it is done ... is it show only or do you want to drive it?

 

For a few hundred bucks you could slap a 1990's chevy truck rear end in it with a 5 on 5 bolt pattern ... You will modify the rear end to fit the car, not modify the car.

So you could slap a newer rear end in it and drive it while looking for a real replacement.

If your goal is a show car then good luck with your search, I will certainly share any info if I see one.

[belvedere]

You’ve probably already checked, but Andy Bernbaum and Deception Pass both have lots of NOS parts.

[James_Douglas]

Hi All,

 

I have checked with everyone mentioned here and then some.  The big deal is that the larger cars used the ring gear that uses 12 bolts where all the other cars used one that is 10 bolts.  That is the quick way to tell the difference.

 

I have a lead on a couple of Limo's in a yard that may have one. Waiting to hear back.

 

Also, I just purchased a set of gears that MAY work. They are a 4.3 to 1 ratio.  I was looking for 4.11. I have the NOS 4.5 set but I am loath to use it as if it came out of OD at 60 the engine would be close to redline.

 

The 4.3 set should be here in about a week and I will see if they look like they will fit. I found the part number for the 4.3 set in an odd way. The big 1946 to 1954 MOPAR Master Parts book does not show it. The 1946 to 1948 Chrysler Master Parts Book does not show it. But the early year production 1946 only Chrysler Master Parts Book shows it and does not show any 4.11 gears.  I think they were using left over 1942 production parts.

 

I checked the case, spider and all the other parts and the part numbers are the same as the later 4.11 gear listings. We shall see in a week if the $200 for the set pays off or not. 

 

Industrial Archaeology is so much fun.

 

James

 

 

[Sniper]

I wonder of they use the same ring and gear as the trucks?  If so Vintage Powerwagons is putting together a run of new 4.30 gears, nothing lower though.  Don't forget if you have the room a taller rear tire can lower your effective gear ratio.

[James_Douglas]

I checked with VPW's and they do not have it.

 

The big reason I did not have a custom 9 inch Ford made was that there is not enough room to move the flanges in so that the wheels/tires can clear studs. None of the axle makers make a flange deep enough for lug bolts.

 

The fender skirts hang down so low that you can JUST get the tire out by jacking the car up by the rear axle. Any taller tires or the use of studs requires jacking the car up by the body and allowing the rear-end to hang down to get it out. My friend has the same problem on his 1946 T7C Convertible.

 

On the side of the road I really don't want to have to pull the bumper jack out and pull this 5000 pound beast that far in the air. Nor have AAA trying to do it for me. I want to be able to jack the rear-end up and change the tire.

 

We will see if the 4.3 will work and then if it does I will see how it drives...If it is usable for the time being, I can then keep my eye open for another 3.91 or 4.11 set.

 

James

 

 

[Bryan]

You must have one heckuva garage and tools. It sounds like changing R&P is as casual as changing socks.  I did one on a 92 Dodge Dakota about a year ago. Was a pain, would NOT want to do that very often.  Biggest issue was getting the crush sleeve to compact (had to use a floor jack), setting pinion load in inch/lbs and getting the depth correct. 

[Sniper]

They make a solid spacer and shim retrofit to do away with the crush sleeve for the Dak, our Mopars don't use a crush spacer so that is one less aggravation.

 

http://www.ratechmfg.com/chryslerspbs.htm

[James_Douglas]

I have the Miller Tool for setting the pinion without the need to press on and press off the bearing to get the shims correct. Makes it possible to do it at home and not pay my rear-end shop for it...

 

One has to take their time and follow the steps. I rebuild the 3-speed and BW-OD and have run it for 50K plus miles without issue, again taking ones time and following all the steps.

 

James

[Sniper]

Three key things to making any job "simple".  the right tools, the proper knowledge and the patience to do it right.  I don't always have them all lol.

[keithb7]

An old Mopar differential rebuild is in my future. I look forward to the new knowledge and experience. I've never completely torn down and rebuilt one before. Just re & re.

I had better read up on the subject . See what special tools I may need.

 

I'm in no hurry. At the current pace, I have about 12-16 months of work ahead of me before I get to a diff rebuild. Maybe if spent less time here...

 

I have a few options sitting here. 3 spare diff assemblies and 2 more in rolling cars.   Is the 3.54 the one everybody wants so they can cruise the interstate at 85 MPM? I can't see acceleration being very exciting. I guess if guys a hot-rodding their old Mopars, the 3.54 is the one they all want?

 

I see they also offered some 4.78 and 4.89 options.

 

In summary, in my 1938 parts book I see:

3.54 Special Economy package 

3.73

3.91

4.11
4.30

4.55 (airflow only)

4.78 (7P) Export to Bolivia

4.89 C19 export to Boliva Only

 

Guessing they primarily still had donkeys on winding, very steep hills in Bolivia in 1938? Slow and plenty of toque needed for big old 7P Chrysler Taxis? Top speed could not have been very high with a 4.78 or 4.89.

 

For some reason Bolivia is singled out in the 1938 parts manual. Maybe they had a special agreement with Chrysler Co. 

Edited October 17, 2021 by keithb7