Lull 844 (1970’s – 80’s?) tower (it raises forks 7’ up & down) shuddering and even crashing down.

Generally happens after lifted 2’ up when going back down.
Telehandler tower wear surfaces was cleaned, chains straightened slightly (doubt it needed) it still won’t lower the forks properly after hoisting a load; chains go loose and forks stay put.

Tried cleaning all old gunk off traveling surfaces, no grease applied. No luck

Tried silicone spray lube on those surfaces. Nothing.

Then tried white lithium grease on same. Maybe a bit better

Removed chains to check top pulleys; they roll fine. No better.

Then sprayed white grease into the (8) top holes. Some improvement.

The issue is worse when the forks are pulled back.

With a load, when moving the tower down it usually travels with a shimmy now, didn’t before – it would fall instead. Then the way to get the load down then is shake the boom carefully.

With no load, the tower works just fine.

I hesitate to apply grease to tower since the wear pads can’t use it for the boom.

Our Lull Model: 844TT- 42 (ft.) / SN: 0746-VTN HIGHLANDER

The oldest manual on it that I can find is dated 4/1/1999.

Can’t find any details on the serial # either.

Take a look at the velocity fuse (prevents free fall of the mast if a hose breaks) at the base of the cylinder. These can be touchy and can get damaged pretty easily.

I just reread your post and I missed where you stated the chains go loose. The velocity fuse won't cause this. There has to be something causing the carriage to bind up such as clearance between the rollers and mast or the adjustments too tight. It's been a long time since I worked on one of these so I don't remember the particulars of the design.

I agree with Bill. Something is hanging up in the carriage if the tower cylinder goes down and the chains get loose. Something is bent or worn causing the hang up. Look it over for pinch points.

Something is preventing it to slide. We have 'slicked up' the roller area a lot with thin lubes. That helped a bit so we can jiggle it down if needed, no crashing.

I can move the carriage around a bit by hand.

I unbolted two of the rollers and can see no problem, none are binding. There is no adjustment for them. Some bolts were a bit loose so tightened em to no avail.

Can't find any failing welds or bent metal.

Will have to figure out how to get the outside section off to see what the 7' base looks like.

Are you sure the rollers aren't dragging the mast? It sort of looks that way but that may be just how it looks. Also check and be sure you have equal chain tension or it will hang crooked and drag.

Thanks for the input!
I'll look into the rollers & also see if I can do more with the tension. I've moved the chains to run straight & visually close to equal.
Not sure if the chains need to be near tight or have some slop.
I'll post any changes...

I was thinking rollers too. Maybe full of old grease and just need a good cleaning? ISZ

I think it was old grease too!
I had leveled the tension a while back and it still is good as can be.
I had removed all gunk possible and used white lithium spray lube & silicone instead; it's getting better all the time; no crashing now - just occasional shimmy now which is not an issue.
Thanks for all the input!