Angle Drive Failure - possible causes - bowed springs and being 1.5mm too long

[DrJeff]

Held a tech day yesterday, and one of the cars had a sheared off angle drive... not failed (as in not spinning)... all that was left of the angle drive was a stub and some threads into the spindle nut. My car (also lowering springs - same replacement angle drive) just had the new spring and angle drive fitted and the angle drive was striking the spring as you turned the hub (or steering wheel - if there was linkage fitted). When the tech day car was lifted in the air, the hub could not be turned at all because it was striking the spring. When we lowered the car onto it's wheels (with the wheels turned as that was the only way to get the angle drive on), the spring retracted and opened up a gap of at least an inch to the angle drive. If this car were to be jacked up again, with the front wheels straight the spring would again conflict with the angle drive. If this kind of spring/angle drive spacial conflict is common, it might explain some of the failures with the angle drive.

The replacement angle drive (on both cars) had a tendency to move in/out from the spindle nut about 2mm after bring fitted and flopped about more loosely than you would expect. It would be the opposite of what you would call precision - to be polite. I had both the spindle nut, the stock angle drive, and the replacement angle drive off my car, so I took the opportunity to track down the source of the 2mm+ movement and the source of the conflict with the spring.

This photos shows the difference in height between the stock (left) and the replacement (right) angle drive. The greater the height the closer the angle drive sits to the spring coils. The replacement angle drive would sit about 5mm closer to the spring.
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This photo shows the difference in the shaft length of the stock (top) and replacement (bottom) angle drives. The shaft extends into the spindle nut. The shaft has a groove in it in which a clip (circle of spring metal) sits to hold the angle drive into the spindle nut. The key dimension is from the base of the spindle to the grove. This is the dimension that holds the angle drive in the spindle nut. On the stock angle drive this dimension is 10mm (including the bevel). On the replacement angle drive this dimension is 12mm and there is no bevel.
41665

This photo shows the bevel in the spindle nut. The stock angle drive shaft also has a bevel, and thus sits into the spindle nut by about 1.5mm.
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This photo shows the bevel at the base of the stock angle drive.
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This photo shows the stock angle drive fitted to the spindle nut and locked in place with the spring clip. The stock angle drive moves in/out about 0.5mm (maybe less).
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The sum effect of these dimensions is that replacement angle drive shaft is about 2mm too long. This is the source of the replacement angle drive play in/out and also wobbling also once clipped into the spindle nut.

I'm guessing, based on these measurements, that the amount of play in the replacement angle drive, both in/out and slight wobbling, and the potential (increased by the greater height of the angle drive) for conflict with the springs, could sources of the increased failure of angle drives.

[content22207_2]

Dave Swingle reported this problem (gear housing hitting the spring) on Houston's latest angle Drives when I spoke with him last year. He also reported that they don't have any provision for lubrication (no screw or grease fitting).

Other than inadequate crimps on the worm gear barrel (to grip the lower speedometer cable), I have had excellent success with Houston's earlier version. Later version definitely seems problematic.

End plates on the earlier drives are staked on. I'm not sure how you would remove the end plates on the latest drives. I had to take my earlier drive apart to pot a 1/8" square post in the worm gear barrel to compensate for its inadequate crimps. If you've got an earlier Houston drive that isn't spinning the lower cable, and if the gears are still OK, this is how I fixed mine: http://www.dmctoday.com/showthread.php?1381-Angle-Drive-Behind-The-Curtain

Bill Robertson
#5939

[Morpheus]

Rather than start a new thread, I figured I would post this here:

While doing some suspension work, I removed my original angle drive. My speedo bounces quite a bit, so naturally I was wondering if there is a way to clean/lube the AD while I have it out. This one doesn't have any visible way to service it. It works, so I am hesitant to just replace it. Any ideas?

[DrJeff]

Hi Morpheus, that is the style of the replacement (not original stock) angle drives. They appear to be sealed (this not lubable) although I was tempted to pop the plate off the end (stamped with 08-12) just to see how they operate inside and gear design.

[PJ Grady Inc.]

Hi Morpheus, that is the style of the replacement (not original stock) angle drives. They appear to be sealed (this not lubable) although I was tempted to pop the plate off the end (stamped with 08-12) just to see how they operate inside and gear design.

These replacement angle drives have proven to be unreliable and inaccurate. We have gone back to rebuilding the original Smith Instruments units again and are considering another batch of "hardcore" gear sets as they proved very reliable. Of course Bobzilla has threatened a more modern electronic fix for years and my next push after the new Lockzilla remote launcher system is complete may be to get on with a speedometer "final solution"!
Rob

[Morpheus]

Hi Morpheus, that is the style of the replacement (not original stock) angle drives. They appear to be sealed (this not lubable) although I was tempted to pop the plate off the end (stamped with 08-12) just to see how they operate inside and gear design.

So this one is a replacement? Interesting. I figured it was stock but since it is missing the screw it must not be.

With no way to clean & lube the thing I guess my only choice is to buy new. Damn.


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[DMC5180]

With no way to clean & lube the thing I guess my only choice is to buy new. Damn.


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That's the whole point, it's to keep you coming back.

The reality is most people never bother to service the AD when they had the ability to do so, either by not knowing it could be or just plain not bothering with it. I'm part the second group. As a 2nd owner I have know idea if the 1st owner had a failure or not, but my first AD failure was in 96 on my way to my first DMC event, DOA expo 96 Nashville. I had my Smiths AD rebuilt by Rob G. That unit lasted about 10 years but still failed. The next AD, New remanufactured came from DMCH but W/ grease fitting. That unit is still going strong today, probably because I bought spare in anticipation of a failure.
I also knew the supply was dwindling of the new replacements and did not want to be stuck without one should the one I had installed failed.

Even with regular service the original ADs had a 99.9% failure rate. Of coarse you still have low mile cars out there that still have OE AD's in them (for now). Let's face it, mechanical drives only last so long.

I wonder how many ADs have been replaced during accumulation of the 675,000 mi on the Hollers BTTF delorean?




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[ssdelorean]

These replacement angle drives have proven to be unreliable and inaccurate.

My car agrees.


We have gone back to rebuilding the original Smith Instruments units again and are considering another batch of "hardcore" gear sets as they proved very reliable. Of course Bobzilla has threatened a more modern electronic fix for years and my next push after the new Lockzilla remote launcher system is complete may be to get on with a speedometer "final solution"!
Rob

If you go back to your HCR drives keep us posted - and put them on your website! Not much there now but I am told you have alot of new stuff.

Martin G's source for his angle drives was hard to work with from what he said but their product was (and still is on my car) rock solid.

[Gregadeth]

Man what is it with these cars and angle drives.

I noticed my replacement angle drive was also longer than the old one, but I checked and it wasn't hitting my spring. I still have my original springs on there though. Also noticed the nut part would go in and out about 2mm like you mentioned. Because of these two things I thought maybe they made these changes for it to somehow improve functionality (?)

Since installing the new one, my speedo now works but isn't accurate. At low speeds it's ok, but when going 65 my speedo shows around 55. Not only that but at the higher speeds the speedo sometimes starts bouncing around as well.

I wonder if maybe my upper speedo cable needs to lubed and/or my speedo needs calibrating. I only replaced the dust cap, angle drive and lower speedo cable.

[DMC5180]

Man what is it with these cars and angle drives.

I noticed my replacement angle drive was also longer than the old one, but I checked and it wasn't hitting my spring. I still have my original springs on there though. Also noticed the nut part would go in and out about 2mm like you mentioned. Because of these two things I thought maybe they made these changes for it to somehow improve functionality (?)

Since installing the new one, my speedo now works but isn't accurate. At low speeds it's ok, but when going 65 my speedo shows around 55. Not only that but at the higher speeds the speedo sometimes starts bouncing around as well.

I wonder if maybe my upper speedo cable needs to lubed and/or my speedo needs calibrating. I only replaced the dust cap, angle drive and lower speedo cable.

Upper cable failure is rare, but lubing the inner member with lithium grease is a good thing.


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[dn010]

I am still on my original angle drive with 78KMI. The crappy OE cable going from the dust cap to the drive shredded on me once soon after I got the car. Pissed about it, I jammed an Allen 'T' wrench into the drive and cut the handle off at the proper length. Hammered the cap end of the wrench flat and made a slot in the cap to accept it. There is no more slop, bouncing or issues with that cable being replaced with something solid! It seems to still be pretty accurate although I do have another original angle drive as a spare 'just in case' that day comes soon...

[DrJeff]

I can across a picture of an Angle Drive for some Triumph cars and noticed that the angle drive looks very similar to the design of the stock DeLorean angle drive (specifically the small screw for lubrication access).

http://www.englishparts.com/products/Triumph/Spitfire/ADAPTOR--ANGLE-DRIVE-TO-SPEEDOMETER-CABLE---BN4-THRU-BJ8--MGB-1962-1980--TR3-TR4-TR6-TR7--1975-1976--SPITFIRE-OVERDRIVE-ONLY-ANGLE-DRIVE--GEAR-BOX/7143622/120694.html

Jeff