I need to give the support trunnion in front of the rear diff some attention on the 988b. Its got some slack ( gap ) at the bottom and is hard to squeeze grease into the nipple at the top. Could I trouble someone for info on : Cat 988B ( serial number 50W03844 ) Q 1. Is there a roller type bearing inside the trunnion or a bushing that needs replacing ? Q 2. What would be a complete list of replacement parts to do this job correctly. Q 3. Is this a hard job ( compared with refurb of the lift rams )
Some earlier models of cat loaders used a fibre bush in that area.
hi take off plate#2 and check that the bush has not worn through if it is bad you may need to sleeve components to get back to standard size undo the 8 bolts to hold the front and rear support and jack up the chassis to clear the locating dowels if fitted.you can then slide the support off the diff housing be careful they are heavy and awkward to handle buy your self Heads up. The dowels can and do seize in there and can be a real pain to drop the support down
If you do have to remove the axle, one way is to block the machine under the rear bumper, remove the rear tyres, put a large piece of 1/2" steel plate on the ground and lower the complete rear axle assembly with both trunnion supports on to it. The axle can then be slid out sideways from under the machine by pulling on the plate and goes back under the same way.
Not a bad job just big parts that you need to respect! If just replacing the bushings it can be done with axle under the machine but just need a way to lift and block up the machine and beware the axle may want to rotate, so keep that in mind.
Thanks for your prompt replys. So it would seem that this machine must have a neoprene or fibre bushing rather than a bearing in the front support trunnion. I will investigate it some more to see how much wear.
Yes a hard fiber bushing. One possible way to attack the job would be to remove all the bolts that hold the cross member to the frame then replace one on each side with a longer bolt. Then it might be possible to jack back of loader up enough to let you pull one cross member at a time and replace the bushing. Then put the cross member back on and then take the other one off. Of course this would not work if the cross member or pinion housing need machine work to restore the fit. Note also that there are dowels in at least the rear cross member item #7 in parts drawing, these can make getting rear cross member free a bit of a problem if they are rusted tight. Usually the weight of the axle is enough to pull them out. The more I think about it I'm not sure the front cross member will slide forward enough to come off, does the frame dip down too much for that???? Also keep an eye on the brake hose if you are going to try to do this job with axle under machine and chock wheels good!
You may find the attached interesting - as far as Step 9 on Page 3 at least. Then reverse the same steps for re-assembly.
All good advice so far but the "remove the bolts" step is getting a little glossed over and shouldn't be underestimated. They are fairly big bolts and they will be tight. The bolt heads are awkward to get to and you might need to modify a ring spanner to stop them from turning. You will need a torque multiplier and an assistant who knows what they're doing to help hold the heavy tooling in the air. In my opinion you are better off dropping the axle to the floor so you can properly clean the crud from on top of the frame rails. Any rust or dirt that gets under the bolt heads will lead to the bolts loosening and you really don't want that. In summary it's the sort of job you don't want to be doing every week and needs to be done right first time because going back to fix up any mistakes will ruin your day.
Cmark, are you saying that a 1979 988B would not be clean and shinny in that area? I mean it's just a tad over 40 years old!
Guys, I cant Thank you all enough for your your input into this project. Also thanks for this file Nige, its very helpful. I will keep it for the future. I have been thinking of buyng a full workshop manuel for this machine. There are some on ebay. Question : Is the manuel in this link the right for all step x step instructions for these repairs ? https://www.ebay.com.au/itm/CAT-CAT...4da857b0de:g:AJUAAOSwuMFUa8JE&redirect=mobile
The answer is on the cover. SENR7318 is the correct manual for your particular machine. A new one goes for US$644 in paper form or US$355 in CD form. As far as I'm concerned the $64,000 question to the seller would be - "Is it complete.?" Take heed of Cmark's comments. This is big iron and you will need the right tooling, jacking capability, & blocking to suit the size & weight of what you're working on.
By complete that would mean to me that every one of those form numbers listed on that page that says "Service Manual Contents" and has all those numbers starting with "SENR" are included. If in fact they are, then that might not be a bad deal, not sure what the price is for you as I get a message saying they don't post to US. And price says $105.32 Australian! Google claims that is only about $75.00 US so if I could buy it for that and shipping was not too bad I'd be tempted to buy it myself just because!
It is located in the USA but will post to Australia. I have been watching these manuals on ebay for a while now. There always seems to be some put up for sale but I have been reluctant to part with the cash as I am still not sure if it would include the complete disassemble/re-assemble ( pics included ) part of the manual for the whole machine ( needs to be like the file Nige sent me for the trunnion ) Some time ago, I paid for a download copy from an aftermarket company but it didnt have the disassembly/re-assembly guides.
[/QUOTE] Take heed of Cmark's comments. This is big iron and you will need the right tooling, jacking capability, & blocking to suit the size & weight of what you're working on.[/QUOTE] Thanks for the advise Nige. Yes, I have been thinking about what technique/tools I will have to use to get it done. I will have to do this one out in the paddock as the machine is currently on a job a couple of hours drive away from the workshop. Since I only want to replace the fibre bushing/o-rings in the trunnion and not enter the diff housing at all : Is it possible to leave the rear trunnion housing ( back of diff ) in place, and then take off the front trunnion ( as per the file you posted up ) ?.....or will the rear trunnion need loosing to get the front trunnion off ? and if leaving the rear trunnion is possible, .... will leaving the rear trunnion in place, prevent the the axel/diff from rolling ? Sorry if these seem to be stupid questions, but I am not near the machine and am trying to work off memory of the couple of times I climbed under her to inspect it.
hi pretty sure I have a 988B service manual
To start with there is no such thing as a stupid question...... I would say that with the amount of wear/slop you have now removing the front trunnion support while leaving the rear one in place would probably be relatively simple, getting it back on again with a new fibre bush installed and witih most or all the wear/slop taken out might be more of a challenge. Let me throw you a curve ball. You KNOW that you have a major amount of wear in the front trunnion, do you know what you have in the rear one..? It might pay you to jack up the rear of the machine slowly while someone watches both trunnions to determine just exactly how much slop you have in the rear support. If both fibre bushes needed replacing then taking down the complete axle becomes the more logical way to do things. Not saying that doing the front and rear one at a time and leaving the axle in place is not a viable option though. It would entirely depend on what you have available in the way of tooling.
Just going back to the pages in SIS on removing the rear differential it does appear that the front support can be removed without dropping the axle as they don't show anything about the rear support in that procedure. But one point about removing the rear support that one has the dowel pins in it and would not be as easy to get off unless the front support was at the least loosened up to let the axle drop down far enough to clear the dowel pins in the rear support. The parts picture might not be real clear on this so I circled the #7 dowel pins. There is one on each side of the support between the support and the frame. I can see where the front bushing might have more wear as it is open at both ends and as one has to work a little harder to access the grease fitting #3, I could see where that might get missed!
Whether or not the front will drop low enough will depend on the amount of wear in the rear trunnion. Bearing in mind it's a B series and the slop in the front is now so bad that someone is considering breaking the tools out, I'd say yes it will. Also considering the above points, I wouldn't be at all surprised if the nose of the diff is equally worn out .
I would agree with that. "Everybody knows" that the fibre bush is softer than the cast trunnion support or the machined differential pinion housing. I'll tell you that the number of diff pinion housings (and rear diff trunnions) I've seen that looked as though they had been ploughed with a tractor are legion. Yes the bushes were worn but the steel bits around them were worn equally as badly. I guess what I'm saying is don't assume that all the wear that has created the gap you can see will have taken place only in the fibre bush.
I've been watching this thread with some interest as I have a little bit of experience on finding this type of failure and seeing the dismantled result of an observation from doing operational tests on the machine. The way I find this problem while sitting in the cab and running the machine is feeling the extra bump when shifting the machine into and out of gear with the engine rpm raised a little. Moving slightly in forward or reverse and then shifting to the opposite direction makes the thump easier to be felt in the seat and through the steering wheel. I've seen the axles removed later and seen the wear on the trunnions and it was substantial. The fiber bushings running without grease were destroyed but not before putting significant wear on those trunnions. My observation is that if it can be felt by a knowledgeable operator in the seat, there isn't much to save anyway. I absolutely understand trying to short cut the job by not removing the axle on this old of a machine. The damage is there and it is more than likely that inserting another bushing will just be wasting time and money. In your place I would be more apt to start by only taking enough stuff apart to ascertain the extent of damage. Then you can make an informed decision on whether it is worth the expense to repair it properly or not at all.
So if the nose of the diff is badly worn what would be the options : Replace with new part ?... or ..... have it repaired by engineering shop ?
Usually repair would be the cheapest option. RD Williams are also showing a used one in stock.
These housings can usually be built up and machined back to size. The rear one (#16 on Mark's post on page 1) is bolt-on. For that one repair by welding/arc spray and machining is also an option. I'm still thinking you're going to find them both worn.
Might not work for a 988B but one time we had a little 966C at least think it was a C. That had the same kind of problem with the wear on the pinion housing for the rear axle. I believe at the same time we were doing work on the front diff so that was out of the machine. After a little checking found that the only difference between the pinion housing for the front diff and the one for the rear diff was the fact that the rear diff pinion housing was machined for the bushing to ride on it. So as we were going to have the two housings out any how we decided to just have the front pinion housing machined for the pivot bushing and just swapped them around. Just wonder if someone down the road was scratching their head trying to figure out why there was all that wear on the front pinion housing! Agree that there will probably be wear from the fiber bushing on the pinion housing. One might think that the fiber would take the worst of the wear but I think the bushings are more like the cloth backing of emery cloth and just serve as a backing for the abrasive grit it they are not kept clean with frequent flushing of fresh grease. This is not meant to be a put down of the current owner as the problem was probably created a couple decades before he took possession of this 988B!