Hi all I have recently noticed when shifting into forward in any gear at any power train temperature there is a couple second delay after selecting the forward gear and when it engages. Reverse functions normally. Once in forward it pushes good and power train temp runs normal. We always decelerate to change direction. Checked filter and screens and all are clean. Recently removed final drive for brake repair and power train had new oil after repair. Would appreciate any thoughts on what may be the culprit. TIA
Not familiar with 8n but I think it's linkage shifted? Linkage might be worn miss adjusted spool leakage at valve body or excessive leakage at forward clutch piston where it's taking awhile for pressure to build in pack. Pressure gauge might narrow down if you see it taking longer to build or showing a pause then sudden increase in pressure. Hopefully that gives you some ideas
Did the problem exist before the final drive repair ? Dirt ingress perhaps ?
This is a differential steering machine with a pretty complicated linkage connecting the tiller to the transmission, correct..?
Yes 8n is linkage shift but doesn't seem too complicated just a couple shift cables. The problem occurred after the final was done and could be debris. To access valve body to inspect/ clean does one remove the rear plate at the top of the tranny? I'll have to get the local guys with gauges/fittings and a little more know how to test pressures.
If it’s cables it should be easy to at least check the detents. As Nige states it sounds inherently problematic and something that could be sorted without a dealer serviceman.
It may be "just a couple of cables" but the adjustment procedure for them covers 8 pages in the Service Manual. If it was me that's where I'd be starting, if for no other reason than to eliminate the possibility that it could be the cause of the problem.
Installed new filters (steering and trans) after brake repair? If the steer filter loaded up with debris and opened the by-pass valve due to restriction, that will contaminate the system. Access to priority valve and selector valve body is via removing the cover plate @ upper rear trans case. Plate removal is required to adjust shift cables also. Test P1 and P2 pressures and 'differential pressure settings' in froward and reverse.
Is there also a delay when changing speeds when already going forward?
Sorry for delayed response we have not been using the dozer as busy finishing up harvesting. Run dozer some more and now we have about a 4 second delay before forward engages. Also when shifting speeds we get a brief hesitation. Reverse works perfectly.
Sounds like you may have to go into the control valve. Something's either blocked of stuck somewhere.
Thanks Nige! I will remove trans control valve, have a look and clean it up.
HeavyEquipmentForums When you tear into that valve to clean it just remember that there are a couple of orificed plugs and screens that you may not even realize are there.... like #12 & #31 in the illustration below. Refer to the link above.
Nige You NEED a service manual. Illustration to ID the four control valve hold down bolts (use tape to hold them up to remove-install control valve), torque valves etc. Post Serial #
Preaching to the converted Stanley ........ However you can lead a horse to water, etc, etc. Personally I wouldn't recommend to go near anything without a Service Manual. Anyhow, just for you, here is the D&A. The transmission control valve appears to be the same P/N whichever of the four possible Serial Number prefixes of D8N are selected.
Sorry you interpreted > Nige as preaching. I WAS SURPRISED YOU HADN'T REQUESTED A SERIAL NUMBER per your' typical posting history when replying to Cat equipment threads. OFF-TOPIC My Laptops with SIS_ET do not connected to the internet. To transfer file(s) from SIS requires coping the file(s) to USB and using PC allowed to connect to the internet OR quick swapping hard drives (5 minutes). Co set-up by an HEF member in my neighbor hood who provides (all brand OEM) diagnostic software, training (individual, large corporations) , on-site support and consulting services @ $108.00 per hour. He is sharp, 25yrs Cat dealer (taught class I attended 98) and 18yrs independent consultant. He sells his time and experience ... SO OP now has 8N D&A file available to read and study before taking on trans control valve removal, careful-disassembly, inspecting-cleaning, reassembly and installation. D&A for priority valve would be helpful also for the OP. Long day, my *** is worn out. I not going to go outside, unlock service truck, dig into SIS, copy the file to USB and use desktop to post into this thread.
Thanks for the sis on the trans control valve. Really appreciated! Scott
Hey folks well removed trans control valve and after reading sis decided to drop off at finning to let them clean it up. They indicated they found some small foreign material in it and sludge. They cleaned it up and i installed it. Run machine and it still has the delay. However reverse seems to engage even better than before haha. I checked the cable adjustment after reassembly and the shift linkage fully engages the detent in the shift spools in the control block so thats not an issue. I am concerned we have an internal issue with the transmission that will require removal and repair. I will have finning come out to test pressures to try and pin point the issue but their tied up for a few days. Problem is if we must remove transmission we have to remove riper and riper frame cause this one does not allow tranny to come out without removal due to frame being in the way. Now my Two part question is are there any other ideas on what may be causing the delay and HOWS THE BEST WAY TO REMOVE THE RIPPER? Block it up and remove barrel pins drive away and then remove frame or just block up and unbolt frame from tractor. Its a 4 barrel single shank ripper. Not sure of make but could possibly take a picture and post later. thanks guys !
Read reply by AmeriIndependent (Rick) HeavyEquipmentForums Hesitation forward speeds caused by 'slow filling' forward clutch; directional clutches (frw-rev) have to fill 1st before speed clutches engage = Power Shift Slow Filling, possible causes 1) damaged sealing rings, takes extras time to seal 2) worn out frictions and disc, extra movement = increased oil volume required to fill the clutch area...both together. You have Finning service tech coming out to check pressures and paying travel time-mileage. Consider having Finning remove Ripper,Trans and Rebuild. Total Service Hours over 25,000? With the trans removed the pinion gear's pre-load should be checked, requires special tooling. AND bevel gear's bearings should be checked. Pennies saved / dollars spent at a later date.
It's looking more & more like the start of a clutch failure TBH. One question though. Did Finning bill you for a new 9W-9830 screened orifice when they rebuilt your control valve..? Because if they didn't they chould have..! It's only $10 or so. Also did they fit a new 7G-9476 Orifice Plug in it..? That would be less likely but still possible if the tech who was doing the teardown was experienced with transmissions.
Hey guys, well Nige and StanRus you were correct. Finning out to test pressures and once engaged forward clutch takes about 6 seconds to build pressure. When Reverse is selected clutch pressure is immediate and to spec. Looks like we are going into the transmission. Nige they did put in a new screened orifice and a new plug too. Thanks for all the help fellas its much appreciated!!