Differential diff lock actuator cheap fix air conversion (1 Viewer)

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My rear diff lock actuator was having extensive damage. It was full of rust inside, all gear, shafts everything heavily rusted and completely seized, the motor rotor was falling into pieces, i live in Canada where road salt in winter affects everything. I called dealer and i did not want to spend the 1500$ he wants for it so i designed a air actuated diff lock actuator. I did it two years ago and it worked perfectly since then. It cost me about 25$ to do it. I purchased a air cylinder and a solenoid valve on Ebay I have attached pictures of the dissambled and reassembled actuator. I installed a Oring in the groove on the cylinder head. The actuator rod is made with a 14 mm bolt. I drilled one hole at the end to attach it to the cylinder with a threaded rod and one hole on the side for the fork inside the differential. I also attached a autocad drawing of the mounting plate. If you access to a milling and a lathe with minimal knowledge than you save 1500$ in about 4 hours. I already had an air compressor in the truck for the air lift suspension. . It is working like the OEM one, with the switch on the left side of the steering column (i bypassed on wire at the diff lock controller behind the passenger side kick panel). I hooked the cylinder up to the 12 volts 4-way 5 ports solenoid valve at 30 psi. The only diffence between this and the OEM is that I can turn the diff lock on even if the center diff lock is not on.

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Mmmmmm- Cable!

Very nice job on the air actuator.

-Spike
 
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I am working on one for mine too! Did you use a double acting cylinder or spring return and what is the bore of the cylinder?
 
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Air suspension? Do tell more
 
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Awesome, nice work and great ingenuity.

Do you have a larger dwg?
 
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Answers to questions:

The cylinder is double acting and is 32 mm diameter and 25 mm stroke. The system needs a 19 mm stroke. I installed a spring the cylinder to limit the stroke to 19 mm but if you keep 25 mm should not be a problem. The springs also make the system fail safe off in sense that if i have a problem with the solenoid valve, i can disconnect the hoses and it will return to off position and i will not have crawl under the truck at the wrong time (with my new suit and make my wife very mad).

This is my first post, i thougth i was able to post as many times 135 kB pictures but i realize that i can't post more than 135 kB total. Those intersted in having all the images can send me a message with your e-mail adrres and i will gladly forward you the autocad drawing of the plate and all pictures.

I also thought about a cable actuator but it would have been more difficult to have it sealed correctly and also you have to push in to actuate the diff lock, you would need rods and all sorts of things that will rust and seized.

I am pulling a 6000 lbs travel trailer with the truck and rear end was very low when i pull so i added air lift www.airliftcompany.com to raise it. I have a compressor connected to an air swith that maintains pressure to 30 psi (compressor starts at 30 and stops at 45psi). This pressure feeds the solenoid valve for the diff lock actuator and also a pressure regulator that feed the air lifti adjust to 25 psi when i pull the trailer and 5 psi when and i am not.

I found lot of interesting topics on that site and i read a lot but this time i will try to help a bit.
 
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Clutchee

I'm fun sized!
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Romer.....save this thread for tech link!:grinpimp:
 
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Claude S said:
My rear diff lock actuator was having extensive damage. It was full of rust inside, all gear, shafts everything heavily rusted and completely seized, the motor rotor was falling into pieces, i live in Canada where road salt in winter affects everything. I called dealer and i did not want to spend the 1500$ he wants for it so i designed a air actuated diff lock actuator. I did it two years ago and it worked perfectly since then. It cost me about 25$ to do it.

Great job Claude! Question: Did or could you use this actuator as a vacuum actuator?

In the Audis that I work on, the air locking diffs (1982>1994 ALL) are vacuum actuated using a vacuum tank resevoir and pneumatic switch (pre 89) or electro pneumatic switch (89>1994). They have some pretty hefty pull at only 17inHg

This could eliminate the need for a compressor in the circuit.

Just a thought.

SJ
 
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I think it would also work with vacuum, the cylinder is 32 mm diameter or 1.25 sq in. in surface and you need about 10 lb to engage the lock. This means you need about 15 in. Hg of vacuum to engage it. What i like with my system is that i know if there is a air leak in the system because the compressor will turn on and off continuously to compensate. When you have a vacuum leak, the engines runs rough and it is difficult to pin point the leak.
 
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Way cool - sent an e-mail requesting the pics and files. Tried to rebuild my rear diff lock - too far gone. Was thinking about a cable lock but this would be alot better - already have on board air.
 
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Claude S said:
I think it would also work with vacuum, the cylinder is 32 mm diameter or 1.25 sq in. in surface and you need about 10 lb to engage the lock. This means you need about 15 in. Hg of vacuum to engage it. What i like with my system is that i know if there is a air leak in the system because the compressor will turn on and off continuously to compensate. When you have a vacuum leak, the engines runs rough and it is difficult to pin point the leak.

Some of us have a lot of experience in that part! Clamp the vacuum hose at the manifold, or use the mityvac. The reason I ask Claude, is that audi also makes a electro vacuum relay box that is really slick. It defaults to unlock (engine off), has momentary contact on/off switching, and has a ground interrupt that can be used for speed, override, or any other ground signal. The early air lockers used a vacuum rotary knob that looks almost identical to the locker switch in the 80. With a really cool lit axle grid with LED indicators.

A couple of ck valves, and a passive vacuum tank. It's quiet, tested on a million air lockers, and requires no electric. I can't pump up the air mattress tho!

Scott Justusson
 
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I know, I know... Holy, thread Resurrection, Batman!

Just wondering if anyone has a CAD file for the actuator plate w. bolt holes. Can't seem to get a hold of the guy who started the thread.

If so, PM me and we can figure out emails, etc.

Thanks in advance,
 

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