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500 Flex Plate and Starter Bendix problems

Started by The Tassie Devil(le), January 02, 2016, 04:07:53 AM

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The Tassie Devil(le)

G'day all,

Firstly, a Happy New Year to everyone.

Now, has anyone else experienced a mismatching of Flex Plate Ring Gear and Starter Bendix in a Eldorado 500?

I had the necessity to replace a worn Flex Plate on a '71 Eldo I was working on, and everything was working okay, till the Ring Gear started to lose its' teeth, until the car wouldn't start.

Upon inspection, there were 10 missing teeth around the circumference, and this also resulted in the starter motor seizing as one of the broken-off teeth got caught up in the guts of the Starter, jamming the armature against the field coil.

I inspected the Flex Plate, and found that the teeth contact with the Bendix wasn't really that good, and that the Bendix had destroyed itself, losing a tooth.

Plus, notice how the ring gear itself runs at an angle, and in second picture, it shows the angled wear on the teeth.

The supplied Ring Gear was stamped "Made in Mexico".   Further, the outside diameter is slightly less than the original Cadillac part.

A replacement Ring Gear was supplied under warranty (also made in Mexico), plus I installed an Original spare Cadillac Starter Motor that I was keeping as a spare.

Now, after a year of use, the car came back with a jammed Starter Motor, caused by the teeth locking end-on with the Ring Gear teeth.

Removed the starter, and found that the Ring Gear was worn, but no teeth missing, but the Bendix was badly worn, causing the misalignment.

I have replaced the Bendix, so the car is still driveable, but now looking for an original Cadillac Flex Plate, plus a Bendix, as I know this will be ruined, but hopefully, not before the replacement parts are sourced, and arrived.

Is there such a thing as a Flex Plate available from Cadillac for the '71 -'76 500?

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Scot Minesinger

Bruce,

Thanks for making us aware of this.  Never seen that before either, but these crappy reproduction parts sources do not make this a surprise at all unfortunately.

I replaced a flex plat when engine was out, just because, and thought I was doing something good.  About to start car up in next week or two and will be watching for this.  I did save the original which was working.

Have replaced a lot of starters, but no flex plates that have left my garage.

Thanks,

Scot
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

"Cadillac Kid" Greg Surfas 15364

G'day Bruce,
and a happy new years to you too.  I'm going to ask you a stupid question. Did you check the Bendix clearance when you installed the starter? too little or too much will not allow the Bendix gears to engage properly, leading to miss-engagement and wear as described.  I looked at two flex plates I have, one solid and one "open faced", and although one of them has a slight angle to it neither comes anywhere near the angel that appears in your third photo.
I would suggest you install the starter and as you manually extend the Bendix, see how it engages.  You may have to adjust the starter by either shims or machining the case as the adjustment requires.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

beastly beauties

Bruce,  I read your article and was curious myself because I purchased a flex plate a few years back. I noticed some well worn teeth on the now installed , possibly original ring gear. I figured I would eventually replace it. My intention was to gather parts for a future rebuild. It appears that I too have one made in Mexico. I unpacked it and checked for a misaligned or pitched ring gear. It is now straight and true to the hub. The supplier on the original box says it came from Roger Chavez Auto Supply Company, Los Angeles, Calif.. Maybe he is aware of similar issues and a cause. I would be interested in finding out your outcome in this matter. If I can help out further, let me know. Good Luck and Happy New Year to you.   David Symonds

The Tassie Devil(le)

Quote from: "Cadillac Kid"  Greg Surfas 15364 on January 02, 2016, 12:02:56 PM
G'day Bruce,
and a happy new years to you too.  I'm going to ask you a stupid question. Did you check the Bendix clearance when you installed the starter? too little or too much will not allow the Bendix gears to engage properly, leading to miss-engagement and wear as described.  I looked at two flex plates I have, one solid and one "open faced", and although one of them has a slight angle to it neither comes anywhere near the angel that appears in your third photo.
I would suggest you install the starter and as you manually extend the Bendix, see how it engages.  You may have to adjust the starter by either shims or machining the case as the adjustment requires.
Greg Surfas
Nigh on impossible to alter the alignment with a 500 Starter Motor as it bolts hard up to the Bell Housing.

And nigh on impossible to see and check the clearance.   Remember I am laying on my back, as the car is on Jack Stands, and there isn't much room to move a big body like mine.

The only way to get the starter motor back any further is to mill an amount from the starter mounting flange.

There was no problem with the original Flex Plate, as Cadillac made it, but the replacement was slightly smaller in diameter.   But, I was told that the replacement part was correct, and the seller had never heads of any problems from previous customers.

The attached pictures are showing the differences between the original plate, and the first replacement, and the Bendix shows sufficient tooth contact.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

"Cadillac Kid" Greg Surfas 15364

G'day Bruce,
With all due respects you really know what is wrong.  The difference in flex plate sizes is just about the size of the notches taken out by the (turns before engagement) Bendix.  You CAN move the starter closer to the flex plate by machining the mating surface of the starter, or you could just get the correct flex plate.  MTS would have the stock flex plate (I believe) or you could get a high performance (I forget the initials) one.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

The Tassie Devil(le)

G'day Greg,

I don't really want to have to machine the mounting holes, and sleeve them as I want to find the correct part.   No good modifying the part, then having to undo the modifications when the correct size wheel become being made.

Further, the mounting holes in the Eldorado are smooth in the Bellhousing, and threaded in the Starter, plus the registering hole in the bellhousing for the starter drive would also need machining.   All this would require the transmission being removed for the required machining.

Notice that the teeth on the ruined flex plate are of a different size.

Now, if one could buy a Bendix that was slightly larger in diameter to compensate for the narrower ring gear, then that would do.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

"Cadillac Kid" Greg Surfas 15364

Bruce,
My visualization is that if you shave a bit off the face perpendicular to the bolt threads is will draw the starter in closer to the flex plate. Is that not correct?
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

The Tassie Devil(le)

The way I see it, with the smaller diameter flexplate, the Starter Motor has to be moved closer to the centreline of the crankshaft, by about .75 of a Millimetre.

Then, if a correct sixe Flexplate is fitted later on in its' life, then the Bendix would bind.

I would rather get the correct parts in the first place.

The noise that the starter makes as the Bendix meshes with the ring gear is horrendous.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

savemy67

Hello Bruce,

In addition to MTS as a supplier of Cadillac 500 parts, you might try these guys:

http://www.cad500parts.com/catalog/page29.htm

I have never done business with them, so I cannot say anything good or bad about them.  Their catalog appears to list the correct flex plate.

Living on the beautiful island of Tasmania has its drawbacks, one of which is shipping parts to your locale.  I do not know if the 472 flexplate is the same as the 500, but if you can get help from someone with a master parts book, you may be able to determine if you can use a 472 flexplate, which may be easier to locate closer to where you live.

Like a good marriage, gear teeth are designed to mesh smoothly, not clash.  Based on the photos, your Bendix pinion and replacement ring gear should never have gotten together.

Respectfully submitted,
Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Glen

Quote from: savemy67 on January 03, 2016, 10:34:05 AM

Living on the beautiful island of Tasmania has its drawbacks, one of which is shipping parts to your locale.  I do not know if the 472 flexplate is the same as the 500, but if you can get help from someone with a master parts book, you may be able to determine if you can use a 472 flexplate, which may be easier to locate closer to where you live.


From the 1974 master Parts Book.  Later years might also work.   
Glen Houlton CLC #727 
CLCMRC benefactor #104

The Tassie Devil(le)

I believe I have solved the problem, thanks to Denrep over at the Modified Chapter site, who encouraged me to get down and dirty and pull both starters from the '71, and my '72, and measure each one.   (Original in the '72)   But thankfully I remembered I had a spare 500 short block and used that for the comparisons

Here are the pictures I took today.   

The first two pictures are of the original Cadillac Flexplate, and the measurement from the back of the block.

The second pair of pictures are of the replacement flexplate with the measurement.

It is clearly seen that the Bendix is only contacting half the tooth depth, thus putting a tremendous strain on the part it is contacting.

The first measurement is 8.65mm

The Second one is 11.9mm.

Notice in the last picture that the ring gear is sitting further back on the replacement plate.   If only they had mounted it flush with the front edge, the problem might never have occurred.   Oh, apart from the fractured teeth, as it looks like the metal was poorly heat treated.

I am going to resist machining the back of the Starter mounting flange as whenever a correct flexplate is purchased, it will then require shimming forward.

I have ordered a replacement and will wait a couple of weeks till I have the part, and check it against the original one before I start the transfer.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe