Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 04-08-2020, 03:37 PM   #21
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 11,486
Default Re: Rear end ratio-gear question

Quote:
Originally Posted by Ruth View Post
But if you really want to run 4.33 gears, I say go for it. Just be aware your engine will be screaming at 35-40 mph in high. Not much fun in a "speedster".
I sure don't know about that. I have ran several 4.33 gears in my speedsters with plenty of success. In hill climbing, I can start in 2nd gear and shift to high which is faster than shifting from 1st to 2nd. I raced my speedsters on dirt with 4.33 gears running at WOT on ½-mile dirt tracks without an engine issue. I guess it is all in what you like with a speedster, but 4.33 gears were fun for me. My son is restoring the old 'Crash' Brown Model-A sprint car, and we will be putting a 4.33 in that too.



Quote:
Originally Posted by Ak Sourdough View Post
Brent, I don't know anything about the manufacturing process used in the Model A assembly plant. However, you are right in your first post that the gear tooth shape could not be the same for different ratios even though the tooth count for the pinion is the same.

My experience is entirely with the more modern hypoid gears not the early spiral bevel gears used in the Model A. They are always sold and installed as sets because they are lapped together in final manufacturing steps. That according to a movie shown in automotive trade school in the early 70's about rear axle manufacturing and assembly.

Yes, I agree with the hypoids sets being lapped however nothing that I have ever found in researching this has ever given any proof that Ford lapped them during Model-A production. I would expect this would have been an expense he was unwilling to include, and I am certain this is the major contributor to why 600wt. lube was used in the transmission & rear ends. With the higher viscosity, they would not have needed to have a lapped tooth to still be quiet.



Quote:
Originally Posted by john charlton View Post
Just wondered if someone has put together a 3.78 rear end out of "orphan" parts and did it work OK ???.
Yes John, I have on a couple of different occasions. In one instance, my father drove a '29 Phaeton to the MARC Nationals in Jacksonville, FL. En route, the pinion bearings came apart and killed the R&P gears. We sourced used parts from several vendors in the swap meet and the mis-matched gears were assembled. That assembly was as quiet as a mouse. Another time was on the Great Race when a team from Iowa broke a tooth on a drive gear. Parts came from everywhere that night from local hobbyists and we assembled it and it did well. With the proper weight lube, and the backlash correctly set, you should not experience any issue unless one of the gears is severely worn.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 04-08-2020, 04:01 PM   #22
john charlton
Senior Member
 
john charlton's Avatar
 
Join Date: May 2010
Posts: 1,304
Default Re: Rear end ratio-gear question

Thanks Brent ,good info, so he should keep rolling until he does a full rebuild .

John
john charlton is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 04-08-2020, 04:10 PM   #23
40 Deluxe
Senior Member
 
Join Date: May 2010
Location: now Kuna, Idaho
Posts: 3,774
Default Re: Rear end ratio-gear question

Quote:
Originally Posted by Ak Sourdough View Post
I'd say try them, it there are no tight spots open it back up and put something on the teeth to read the pattern. They used to use white lead, but along with being a hazard, you probably can't get it anymore. A good substitute can be made by mixing chalk dust with gear oil to make a thick paste.


I hope it works out for you.

Or see your local GM dealer for some Gear Marking Compound. It's a yellow paste of the right consistancy.
40 Deluxe is offline   Reply With Quote
Old 04-08-2020, 05:06 PM   #24
ursus
Senior Member
 
Join Date: May 2010
Location: Oregon
Posts: 1,369
Default Re: Rear end ratio-gear question

Helped a fellow with a noisy rear end some years ago. On inspection, the pinion was bad because the pinion bearings were shot. He found a rear axle lying in the weeds in a vacant lot and pulled the driveline/pinion from it. I was skeptical, having become accustomed to seeing matching ring/pinion sets in every rear end I opened. We assembled it with new bearings, checked the contact with Prussian Blue paste, and installed it in his coupe. To my surprise, it ran quiet and smooth. Maybe we got lucky?
ursus is offline   Reply With Quote
Old 04-08-2020, 05:08 PM   #25
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 16,371
Default Re: Rear end ratio-gear question

A person can run a higher numeric gear ratio and install a Mitchell overdrive if you want the best of both worlds. Back in the day they would have likely used an under/over gear box but that would have been more for pickups or trucks. With a speedster, the sky is the limit.

The gear marking compound is made from yellow pigment (pastel chalk as was mentioned) and synthetic oil mixed to form a paste. I started making my own back when red lead was no longer available. In packaged form, it's available from gear shops, Summit, and Jeggs plus many others. GM has a part number and there is an AC/Delco number but I don't worry too much about where it comes from. I just don't want to pay a lot for it. It works pretty well. I liked red lead paste better but such is life.

Last edited by rotorwrench; 04-08-2020 at 05:28 PM.
rotorwrench is offline   Reply With Quote
Old 04-08-2020, 06:53 PM   #26
Ruth
Senior Member
 
Join Date: May 2016
Location: Glide, Oregon
Posts: 1,334
Default Re: Rear end ratio-gear question

Sponsored Links (Register now to hide all advertisements)
Quote:
Originally Posted by BRENT in 10-uh-C View Post
I sure don't know about that. I have ran several 4.33 gears in my speedsters with plenty of success. In hill climbing, I can start in 2nd gear and shift to high which is faster than shifting from 1st to 2nd. I raced my speedsters on dirt with 4.33 gears running at WOT on ½-mile dirt tracks without an engine issue. I guess it is all in what you like with a speedster, but 4.33 gears were fun for me. My son is restoring the old 'Crash' Brown Model-A sprint car, and we will be putting a 4.33 in that too.
I'll admit I was thinking more of a street drivien speedster. Still doesn't explain why he needs 4.33 gears to put it on a trailer...
Ruth is offline   Reply With Quote
Old 04-09-2020, 04:41 AM   #27
Floats
Senior Member
 
Floats's Avatar
 
Join Date: Dec 2013
Location: Mossel Bay, about 300km from Cape Town
Posts: 530
Default Re: Rear end ratio-gear question

Hi John,
I have also replaced a 4.11 set with an unmatched 3.78 pair in my RPU. I got the two parts from two different guys, they looked like a match with no apparent wear. It runs smooth and quiet apart from the other noises a Model A makes.
Take care and be safe guys.
__________________
Regards
Chris
Cape Town
28 Model A RPU, 29 Chevy Phaeton, 67 E Type FHC, 67 250SL Pagoda, 83 911 SC
Floats is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 07:03 AM.