Up next in 10
Mopar axles, after 1959: How they changed, why, and who changed ’em
8K views
Oct 2, 2024
How axles were designed “back in the day” and how they switched to their 1960s-1990s design—and what he would have done differently! (Revised with new images, better image timing and labeling, “by request”) - based on talks with the former head of Valiant body engineering. #mopar #axle #valiant #plymouth #dodge #classiccars #rearaxle #autohistory
View Video Transcript
0:00
Hi this is Dave from Motels and I'm here to build on Pete Dahl's recent talk about axles
0:05
My story here is actually Al Bosley's story. The axle is surprisingly one of the items on a car which requires the longest lead to set up tooling
0:16
So the valiant axle was planned before the details of the engine or transmission were known
0:22
In early 1957 in fact, Al was responsible for the rear axle, the drivetrain and the rear suspension
0:29
even though he was still a pretty young engineer new to the company
0:33
The front and rear suspension designs were then at different departments at Chrysler
0:39
This is kind of an odd idea since they really do have to work together
0:44
Evan Jones was the manager of the axle lab and he had a great deal of experience
0:48
So he would sketch the axle out and write down the specifications and then the drafting department
0:54
would convert them into drawings for manufacturing and purchasing. Evan started working on this axle with Al Bosley at the start of 1957
1:03
They talked a lot about what would be needed but they didn't have a whole lot of information
1:07
about the car that the axle was being designed for. The length of the pinion, the vehicle track, the amount of power or the amount of weight
1:15
They only knew that it would be a light, small car. Al said that Evan had talked with the people who actually made the axles down in Lynch Road
1:24
and they were not happy with the Hotchkiss axles used at the time
1:28
And they concluded that the 7.25 inch axle using a carrier tube was the way to go
1:34
because it provided more flexibility on tread, it was more rigid and it avoided manufacturing issues
1:41
The axles that Chrysler traditionally used were two-piece drive axle arrangement with tapered outer end shafts that fit into a separate flange
1:50
and had a nut and a key that held it together. And they were very hard to get apart if you needed to get to the brakes or change axle shafts
1:57
It was Al Bosley who proposed using a flanged shaft like GM and Ford
2:03
Now since the very first Chrysler in 1924, they always used straight axles with a taper and a bolt-on flange
2:09
instead of using a hot upset process where the end of a bar is heated
2:14
and then forged back on itself to create a larger flange. And the people at the axle plant said that it would be a little more expensive
2:21
but they could still do it and it would be better overall for the car
2:25
The drawings were released in mid-1958 to the Lynch Road Axle Plant and to the purchasing
2:30
and they just started designing the tooling. They ordered the gear cutting machines
2:34
got the casting patterns done and did everything else they needed. Now Al Bosley said that there were two things that he wishes that they had done better
2:42
And the first thing is that neither of them ever thought anyone would run
2:46
300 brake horsepower through that axle and the differential gears in the pin were really too small
2:51
On the lighter side, the short grip versions did hold up better. And the other thing that he wishes he had done differently
2:57
was something that they did to save weight. So in the eight and three quarter inch axle that Pete Dahl talked about a couple of days ago
3:05
the main drive gear pumps oil up to the front bearing along a passageway in the top of the axle casting
3:11
There is a little void along the bottom of the rear bearing so that the oil can get back again
3:16
And they left that out on a seven and a quarter inch axle that was used on the original Valiant
3:21
It turns out that both bearings didn't get enough lubrication so the axle ran a little hot
3:25
Al Bosley later said, perhaps if we had realized that someday we would want to put a 346 pack engine in front of it
3:31
we might have thought about it a little bit longer. In any case, most of these things got changed later
3:37
And he said that he thought that the weight and cost savings for the first three or four years was a good decision
3:42
Now you might be wondering about the small five bolt circle. That's at the end of this axle at either end for the wheels to go on
3:49
They made a choice to use a smaller bolt circle to make the axle shaft easier to process
3:57
To make the upset process easier to create that flange and to save weight
4:01
So the Valiant has a smaller bolt circle than the Chevy or Ford did
4:05
but with five wheel bolts instead of four. The Falcon and the Chevrolet had four wheel bolts on a larger circle
4:12
The wheel maker said that that would be okay. So they were able to cut the diameter on the flanged axle shaft
4:17
I would like to thank Al Bosley who passed this story on to me when he was in his 90s
4:23
And Peter Dahl who did the recent Mopar axle presentation
#Classic Vehicles
#Vehicle Modification & Tuning