Mohawk A7

[winkeldc]

I have been getting some good information from everyone just by lurking, so I thought I would step up and seek help. I bought a house that came with an old Mohawk A7 two post lift. It has the old design connecting the lift arms to the carriage assembly that uses 1.5" pins that drop into place and are held in with snap rings. On the driver's side post, the carriage assembly started to deflect, the bottom is slighly deflected to the point where the long arm is about 3/4" lower at full extension that the rest of the arms. I talked to the local installer and he said Mohawk changed the pin design to use a threaded pin to prevent this from happening. I was told that I would need a shim or two, basically large washers, to place between the lift arm and the carriage assebly before I torque the new pins, and that would level the long arm again. He never got back to me after several calls so I started looking for other sources.

The problem is I don't know how the shims work so that I can get the correct sizing, and the new supplier can't tell me that because they are in sales and not installation, but they are not local so I can't have someone come out. I measured the slack between the lift arm and the carriage assembly, but because its tilted, that number fluctuates front to back. When I lift the arm to level it, I get the same result because of the deflected bottom plate. Do I just order the smallest shim that will fit in the smallest measured gap? Will that actually work because there still would not be a level surface for the lift arm to rest on?

I am new to car lifts, I have always been a hobbyist that just worked from jack stands, but I would like to get this lift leveled so I can use it safely. The Mohawk installer indicated that having the bottom carriage plate, that the lift arm rests on, deflect is common with the old pin design. It was the reason they switched to the threaded pin design, so I am comfortable that the carriage assembly is okay and just needs to be updated, its what he was going to do in a service call. Does anyone have experience with shimming lift arms to level the arm again? I just want to make sure I am going down the right path before I order the parts.

 

[pattenp]

I'm not quite following where these shims are to be place to correct the deflection. A picture is worth a thousand words.

 

[D94R]

And I'd be more worried about the deflected carrier and replacing it, rather than shimming a pin to "correct" the arms.

If its deflected, it's stress beyond it's capacity and I would strongly suggest not using it. They likely moved to threaded pins to keep the plates from deflecting under load because the carriage is under-built.

 

[matt_i]

Just a thought. I understand the basic swing-arm design pivoted around a vertical pin.

However if 3 of 4 are level and 1 is not, I would suspect either wear on pin/bore interface or permanent deflection.

So this gives a couple of cheap and medium-easy things to try.
- Can you lift the deflected arm so its level or above level? Does this same test work on the other arms ? This might help you find the cause of the "lost motion" or clearance in the fit.
- Have you tried removing the snap rings to check for wear on both surfaces, alternate application of this would be to swap similar components side-to-side and see if any change is noted.

 

[rburke65]

I bought a 24 year old Mohawk lift and had cause to call the mfg. in New York. They were very helpful. The do make a good product. Photos would help if you can post. Also a local hyd. lift...repair company might be an idea.....I have gone this route also. Cost me $90 but I learned something and I feel safer now under the lift. Good luck.

 

[winkeldc]

Just a thought. I understand the basic swing-arm design pivoted around a vertical pin.

However if 3 of 4 are level and 1 is not, I would suspect either wear on pin/bore interface or permanent deflection.

So this gives a couple of cheap and medium-easy things to try.
- Can you lift the deflected arm so its level or above level? Does this same test work on the other arms ? This might help you find the cause of the "lost motion" or clearance in the fit.
- Have you tried removing the snap rings to check for wear on both surfaces, alternate application of this would be to swap similar components side-to-side and see if any change is noted.

I can lift the deflected arm so that it is level and above level. The other arms have some vertical play, but not as much. The pin hole in the deflected arm is slightly elongated, but we are talking 100ths of a millimeter. I'll try swapping arms and see what happens.

I may start calling around to some shops and see if I can get an expert to help. I tried calling Mohawk and they were extremely helpful, but then they referred me to the installer that never gets back to me.

I'll try to get some pictures loaded. I think I have some in my email when I was emailing the installer so he could get the parts for me before setting up a service date.

Thanks everyone!

 

[rburke65]

They are good lifts even if you have to spend a little money.

 

[matt_i]

So.... one way to fix this would be to bore out the hole in the arm (and carriage) by 0.010" or until it cleans up.

Then, make a new pin that fits within .002" (-) of the bore. It could be a stepped pin to match the new bore in the arm. Make/have made the pin out of 4140 steel.

The downside of machining just the arm is that if the bore in the carriage is tilted due to its mfg, trying to clean up & align the pin/bore fit to the arm isn't going to fix it. Ideally you'd take both parts to the machine shop and they can establish level and work from there.

I am doubtful of a tapered washer or shim to fix this issue. It seems like poor practice.

Here is what I would do....in my opinion its highly unlikely there would ever be a strength issue with something as large and massive as a Mohawk, so despite the wear or misalignment of the pin bores, I would go out to the other end of the arm and make a new detail that raises the pad enough so its level with the others. Possibly a range of parts with different heights to account for the lift arm being full open or full closed. I believe that would be a solid safe fix that would last as long as the lift does.

Cue the incendiary grenades for suggesting lift mods in 3....2.....1...........

 

[alberto]

Why not just call Mohawk and ask the directly with no middle man involved? With a Mohawk brand lift in hand and an issue like this I'd go straight to them for answers.

 

[Barnabas]

Why not just call Mohawk and ask the directly with no middle man involved? With a Mohawk brand lift in hand and an issue like this I'd go straight to them for answers.

OP said:

I tried calling Mohawk and they were extremely helpful, but then they referred me to the installer that never gets back to me.

 

[D94R]

...the carriage assembly started to deflect...
...The pin hole in the deflected arm...

Wait, which is it? A deflected carrier or elongated hole in the arm? One indicates over loading of the lift, the other indicates wear.
Stressed steal weakens it, worn steel does not.

...in my opinion its highly unlikely there would ever be a strength issue with something as large and massive as a Mohawk

Until the OP clarify's what is wrong, this seems to be the "exception to the rule" if the carrier is indeed deflected. I do say, just one arm experiencing this points to pin hole wear, but we really need more info from the OP.

However, Mohawk uses [redact]threaded pins[/redact] bolts to keep the upper and bottom plates of the carriage in compression now, so they recognized some issue regarding strength at some point after the OP's lift was made.
View media item 73991
Bendpak doesn't use bolts to hold their carriage in double sheer for plate support...

Other than the Bendpak having top plate hole reinforcement welded to it (and its unclear if the bottom plate holes have this) the design between the two is relatively the same in regards to plate support between them. The bendpak does have a massively larger upper plate support going vertical from it though.



Post some pics OP.

 

[winkeldc]

As to deflection and elongated hole question, its a little of both. The bottom carriage plate does not sit entirely flat. I didn't measure the deflection, but I used a level. It's a bit off, but over the span of the arm, it adds up. On top of that, there is vertical play with the arm, and the hole is ever so slightly elongated. So it appears I have two problems. Well, three. I went to swap the long arm from the passenger side carriage and the pin is frozen into the carriage assembly, but the arm still swings so I never thought to check that. I can't swap at the moment.

I am not terribly worried that the lift was overloaded. When I talked with both Mohawk and the installer, they said this was common and the new threaded pins was the fix. Neither suggested that I needed to buy a new carriage assembly after seeing pictures of what I was describing. I couldn't find those, so I'll get some pictures up today hopefully.

I think boring out the hole would be above what I have in equipment given the thickness of the metal. I may have misunderstood the information, but the shim supposedly alleviates the elongated problem by raising the arm enough to become level, as well as lessening the gap caused by the deflected carriage assembly when the new pin is torqued down.

Thanks again all!

 

[skippydoo]

https://www.sviinternational.com
Anyone looking for good quality replacement parts.

 

[winkeldc]

Okay, Here are some pictures of the arm and carriage assembly with a level showing what I am trying to describe.

The first image is a level on the uneven arm, the second is the level on the bottom carriage plate, and the third is on the top carriage plate. The other three arms are completely level, even the short arm on the same side. Also, on that third picture, you can see the gap between the arm and the carriage assembly, the "shim" would go there from what I am being told.

Thanks Skippydoo! https://www.sviinternational.com was the place I am going to order the pins and shims from once I figure out what I need.

 

[pattenp]

That's just plain wear and tear. Worn out hole and pin. The only thing I think would fix that is to have the holes welded and re-drilled and get a new pin.

 

[clubairth]

That's a great comparison photo!
The BendPak arm is just massive compared to the rotary arm.
.
.
.

 

[alberto]

OP said:

Why not just call Mohawk and ask the directly with no middle man involved? With a Mohawk brand lift in hand and an issue like this I'd go straight to them for answers.

I tried calling Mohawk and they were extremely helpful, but then they referred me to the installer that never gets back to me.

My bad, I try not to be that guy that doesn't completely read the Op. Apologies.

 

[RGKSR]

I would call Mohawk. I've had an A-7 for about 15 years. I just added two Rotary SP09's. The Mohawk is super beefy compared to the Rotary.

 

[LXCam]

Maybe I missed this. But have you pulled that arm to verify what is worn. Is it the bore of the arm or the pivot bolt/pin? If it's the arm take it to a machine shop and have them either replace the sleeve or if thick enough reem it and resleeve it. If only the pin is worn that's slam dunk. Based upon your statement for the other arm and you saying the pin is seized in the bore my money would be that it maybe isn't seized but is worn and your catching the lip while trying to remove it. I'd support the arm to were it's not bound in any manor and try a little persuasion with a bigger hammer to get it past that point.

Good luck and as suggested if anything shim the pad and keep an eye on the wear.

 

[matt_i]

In my mind, thinking about it, tt seems nearly impossible it could be a wear issue. Even if you took a can of Clover Lapping Compound (coarse grit) and lubed it all up and swung the arm back and forth for hours every day, it would take a very long time to approach .010" wear on a 1-1/2" pin, even if its dead soft 1008 steel. If its 30yo and has been working in a professional shop the entire time, then possibly yes. But I think you could tell that by the wear on the paint, etc.

I would think some kind of a fixturing while machining or fixturing while welding error in the manufacturing process, especially since the other 3 aren't "worn".

It also seems nearly impossible that a shouldered, threaded pin could be stronger, at the same nominal diameter. It could have better axial retention under loading than the snap-rings in shallow grooves. But trying to smash the supports together via bolt torque would just put the whole thing in a bind and not necessarily correct the pin being out of square and parallel with the carriage.

 

[winkeldc]

Thanks everyone! I had that one pin soaking in Kroil, and was able to remove the pin finally. It had some rust deposits near the bottom. Long story short, I was finally able to swap the arms from side to side and now the lift is level! Well mostly, the locks are at a slightly different engagement point, so its ever so slightly off when it comes down on the mechanical locks, but that is an issue for another day. The higher the lift is raised, the closer the lock engagement points seem to be. Interesting design if that was a design consideration. I have no idea why switching the arms worked as it did, but such is life I guess. So the end result is I won't be buying the shims, but will get those new pins that are the nut and bolt design, just in case.

Just wanted to give an update and a thanks for all the advice.

 

[winkeldc]

Okay, so now that I am working through the arm problems on this thing, I need to get the arm restraints free. Those that have an A7, how do the arm restraints come apart? I can't get the mechanisms to budge, and I can't find anything a parts schematic to show me what I am dealing with. With something being stuck, I am hesitant to start pounding on something I am unsure of how its put together.

Also, what is the easiest way to change the fluid. I need to top off the fluid but because I am not sure what is in there, I'd rather replace. The manual suggests that there is a drain plug under the reservoir, but not on my unit. Since I am replacing, should I just use the pump to pump the fluid out and flush the system with the new fluid? Or just pump the old fluid out with an extractor, replace and call it a day?