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ZF5 installed in November 2016... Approx. 6k miles on it. Rebuild beforebinstall all new bearings and synceos. Gearset is a wide ratio from a 460 trans. Behind a 6.9 with SMF Luk flywheel and clutch. Originally filled with 4 quarts Mobil1 sythetic ATF, fluid changed about a week ago to 4 quarts Royal Purple Synchromax.
Today driving around 25-30 MPH in 4th I downshifted to third, double clutching as I do more often than not, when I let the clutch out engaged in third I heard a pop and crunch and the shifter moved down toward neutral but did not pop out of gear entirely. I also heard a noise like something spinning to higher RPM then stopping. After this the shifter feels somewhat sloppy and harder to get into gear, there is resistance and syncros in any gear don't seem to work as effectively. Once in gear there is more movement in the shifter than isual. New plastic/nylon shifter bushings were installed during rebuild. All gears work and no abnormal noises.
I plan to remove shift tower and inspect tomorrow, maybe drain fluid and check in PTO covers. Any ideas?
I should note downshift to third was to decellerate. So double clutch and slide right in easy but immediate decel load on gearbox when clutch out. Thinking about it today it could have popped out of gear, I still had my hand on the shifter and my immediate reactionw as to put some pressure up into third. I felt the shifter push back towards neutral. Could have popped partially out and ground on the synchro a bit and back in.
Regardless, driving the truck today the trans felt different. Shifter maybe a little sloppy. I feel the slider moving and engaging the synchros and blocking rings much more than previously. It's like a fair amount of the numbness or notchiness of the ZF5 is gone. I was thinking maybe one of the detent spring plugs popped out, but that is not the case, all are present. I do notice a little more stiffness getting it into second gear when slowing to a stop.
I pulled the shift tower and did notice I had one of the shifter bushings in backwards. There is appreciable slop between the bushings and tower when moving the shifter forward and back, slight slop from the bushings rocking sideways in the tower. These were new bushings labeled AMP ordered on eBay. I don't know if these are ZF brand or aftermarket. I suspect the one that I reversed (likely in the past week or two when I changed the fluid) was getting worn down. I ordered two new Ford bushings and will install those and note any change when they arrive.
I don't hear any bad noises, fluid level is still slightly overfilled (4 quarts). I will run it and maybe drain the fluid to check for metal after some miles if no noises develop. I really don't want to pull the trans and pull it apart for inspection. I may keep my eyes open for a ZF6 as a plan B if I do need to pull this trans.. The wide ratio box is nice for moving trailers around but it feels like a lot more spread behind a diesel than a 460. I don't think I'd like the close ratio box with 3.55:1 gears though.
Shifter is tighter now with the bushings in proper orientation. I noticed driving today that in third the shift lever moves slightly forward under acceleration and slightly back under decelleration. The gear is of course moving the opposite direction, rearward under accel and frontward under decel.
I'm wondering if there's a thrust bearing or bushing that may be wearing or broken. Looking at an exploded diagram there is not. The rear thrust surface is a lip or step in the mainshaft, the front thrust surface is the slider hub which is a light press fit and retained at the front of the mainshaft with a snap ring. I checked a ZF5 mainshaft I have mostly assembled on my bench and third gear does have noticeable (but not excessive) free play front to rear. This small free play could be exaggerated over the length of the shift lever and changing the shifter bushing orientation to be tighter in the shift tower would of course exaggerate the movement at the end of the lever.
I'm not sure if I should be concerned or not, given there must be some backlash to spin freely when not engaged. I notice the same type of movement in the shift lever in 5th as well, though much smaller. I'd never notice unless looking for it (lightly holding the shifter engage in each gear and slowly rolling on/off accelerator while feeling for movement). 3rd gear shift lever movement seems more exaggerated. Anyone else notice this in your ZF5?
I may stick with plan of pending no further odd or unusual behavior drain fluid and inspect through PTO covers at a convenient time. I will add checking backlash on 3rd gear to the list while I have the PTO covers off.
Well my ZF5 grenaded today. Decelerating in third while towing. Felt and heard a pop and grind and some other horrible noises. It immediately became hard to shift, unable to move shifter into gears 1-4 at times, then I lost 4th altogether. Shorter only moves slightly towards 4th, feels like slider doesn't even move to 4th. Tried shifting without clutch to 4th and nothing, doesn't go and doesn't crunch or grind. 3rd is hard to shift into, sometimes it feels blocked and won't move, other times it'll go if revs are closely matched. Also began to sound like a box of rocks at idle with clutch out.
1st feels blocked and won't go like 4th but I can get it in if I go to second then first... Sometimes. A few times I couldn't get any gear without about 30 seconds of messing with the clutch and trying every gear. A couple miles from home I heard a squeal when slowing to a stop and had a hard time getting any gear, finally got 1st and went with that until I was in a safer spot then drove in 2nd the rest of the way home. I was able to use first and reverse a bunch of times to get my trailer put away.
So I'll be pulling the trans this week to do a postmortem and evaluate what I need to fix it. I saw a ZF of CL about 5 mins away for a steal but called him and he just sold it today. Just my luck. Not much else in the vicinity if this one is as bad as I expect, so I may bite the bullet and buy a reman S5-47 to have the stronger trans and inbetween gear ratios. Very rare I see a used S5-47 within 500 miles of here.
My theory is the snap ring at the front of the mainshaft broke in the initial event, subsequent excess movement of third gear and the synchro hub assembly wore thrust faces of 3rd, synchro hub, or 4th on decel eventually allowing both 3rd and 4th to become engaged simultaneously upon decel. Kapow, shrapnel, bearings not happy, maybe bent or broken shift fork among the carnage. Not sure why 1st/2nd are having issues though.
It is exactly as I suspected. Snap ring in front of third gear synchro hub broke and remnants out of the groove. Hub moved forward allowing 3rd gear more endplay. Consequence was endplay for 4th decreased to the point the synchro was always trying to synchronize. Cooked the synchro, welding bits of the input shaft/4th gear to it as well as parts of the synchro hub. Lots of metal on the magnet and chunks between 4th and the hub, the end piece of the failed snap ring was inside the input shaft/pocket bearing seal. Input and output shafts were tight in the case, no abnormal wear to those at a glance.
At minimum I need a new input shaft, 3/4 synchro hub and slider, pocket bearing, pocket bearing seal, SNAP RING, 4th gear blocking ring. May as well replace 3rd gear blocking ring as well since it's right there. Not sure why the difficulty getting into first and grinding into second... Maybe because the 4th gear synchro was dragging on the input shaft constantly. Need to pull 1st/2nd as well and inspect teeth, blocking rings and bearings and may as well put new blocking rings regardless. Not my idea of fun when I have a long trip planned 3 weeks from now. It's a tough pill to swallow but I'm debating buying a reman S5-47, then going through this at my leisure for a spare or to sell and recoup my core charge since I don't have a S5-47 for a core. Time is tight so I'll weigh my options.
Such an odd failure, any ideas why this snap ring may have failed? Is it a design flaw with the light press fit of the synchro hub and deceleration thrust going forward retained only by the light press fit and that snap ring? Is this one of the changes in the S5-47? I never had any issues in my 460 truck engine braking. Should I not be engine braking with a ZF5 behind a diesel?
The saga continues... I picked up a S5-47 last night. I can feel a tiny bit of slop in the input shaft but it seems to shift through the gears nicely. As I'm tight on time I'm tempted to throw it in and run it as is, but I think I'll measure endplay in the main and counter shafts and shim it for proper preload if everything looks good.
Endplay is .002" on the mainshaft and approx. .003" on the countershaft. Had a hard time getting a consistent measurement off the countershaft. It's tempting to leave it be and run it until winter but I think that's too much, given the bearings are preloaded in part because aluminum expands more than steel so there will be more endplay at operating temp. It would probably sound like a box of rocks with a SMF. I'll open it up and hopefully I have the necessary shims.
On a side note, PTO covered were mangled at the bottom. I didn't notice originally but the trans was dragged on a hard surface. One was ground down including the lower bolt and the other was just bent on a corner. I'll swap straight ones from the S5-42 on there. Fortunately only superficial damage to the case and sealing surfaces are fine.
No more replies to this thread. I hope I'm not boring everyone... In any event, the saga continues. I suppose I get what I deserve for trying to get away with a quick and dirty.
I got the trans opened up Thursday night. Bearings in the front weren't pristine but didn't look too bad. I shimmed to .002" on the mainshaft and .001" on the countershaft. No endplay in either shaft once reassembled. I could still feel a tiny wiggle in the input shaft, but with no measurable endplay I called it good enough until winter.
Installed trans Friday. 15-30 seconds after starting the engine it started making a squealing noise. Clutch in and it goes away, clutch out and it makes the noise. Noise in every gear with transfer case in neutral. Didn't move the truck any more than just starting to let the clutch out in 1st, 2nd, reverse. Synchros feel worn for sure but not difficult to get into gear. I saw they were very worn while I had the case off so this was no unexpected.
I checked the clutch fork and throwout bearing, removing the fork and pushing the throwout bearing well away from the pressure plate. Noise was the same. I did grease all the greasables on the front end plenty so I did not expect this to be it. I also checked through the fork hole for bent pressure plate fingers, I doubted that as it went on smooth and easy, but nothing bent or looking wrong.
After pulling it out I measured endplay. None in the mainshaft but .006" in the countershaft. Far cry from .003" previously or .001" preload. Pulled the guts and inspected without disassembly, found nothing that would cause such a noise. Flipped the rear case half to clean and inspect and the countershaft bearing race fell out! Cleaned the case and race and it just slides in and out and spins in the case effortlessly. I'd guesstimate a couple thou clearance.
I'm tempted to try using bearing and sleeve retainer and staking it. If I proceed I'll do a full rebuild. Thoughts?
Tore down most of the mainshaft today. Snap ring pliers weren't big enough for the rear of the shaft, must have misplaced them. I'll pick some up tomorrow. Have all new parts coming this week including a new tailhousing. Didn't want to chance it since I'm so close to a long trip towing and new apparently still available. Doing this one on the floor since bench is full and I'm lazy.
Tonight was very short lived. The new rear housing and rebuild kit arrived but I promptly broke a puller trying to remove the rear bearing. Too late to make noise with a grinder and air chisel, I may go that route tomorrow but I'll still need a puller for the countershaft bearings. I'm sick of getting by with cheap pullers and rigging up ridiculously sized and shaped things with random bearing separators all sketchy-like in my small press. My time is worth more than fighting with janky fragile tools even for those few and far between projects. Ordered some good pullers and should be good to bang it all out by the weekend.
I also learned today I should have read the ZF5 troubleshooting manual upon first symptoms.
Excessive Shift Lever Movement in 3rd Gear • 3-4 synchronizer body snap ring not seated in groove on output and fifth gear driveshaft. • DISASSEMBLE and REPLACE affected parts, paying special attention to 3-4 synchronizer, input gear, input shaft pocket bearing and shift fork.
The rebuilt S5-47 is in and working well. I notice the S5-47 shifts appreciably nicer than the S5-42. Synchros work better at high RPM differential between gears, though it is not as wide of a ratio. Reverse a a little notchy and take more effort to get into. This may be the blocking ring taking a little time to wear into the cone on the gear, or it may be that I put the better used slider on 5-R rather than the new one I put on 3-4. When I tore it down the reverse synchro was totally worn out and doing nothing, and the teeth on the slider were thoroughly trashed. The teeth on the gear showed some wear but weren't terrible. I did install a new 5-R fork as the reverse side showed appreciable wear. Also put a new 3-4 fork in, that one showed less wear but it was cheap and I could get one quickly.
Common misinformation is the bearings are different, they are not. All bearings from what I can tell are identical to the S5-42. The mainshaft I believe is also the same, some gears on the countershaft are the same and others are different for the different ratios.
The cases are visibly different if you know what to look for. The S5-47 has a rectangular protrusion on the bottom just forward of the drain plug, there are differences in webbing internally and externally.
The synchros are different. The main difference I can tell is the keys in each synchro hub are a sort of rectangular wedge with a spring directly between the hub and key. The S5-42 has a more traditional flat rectangular key with a ball through a hole in the center which the spring acts on. The S5-47 synchro keys are much easier to install and from seeing how they actuate, I suspect they exert force more effectively on the blocking ring.
The sliders are different. They have a larger area to lock in under load. The teeth on the gears are different, the have limiting stops for the slider and a more pronounced back-cut on the teeth. The sliders for 3-4 and 5-R are interchangeable and can be installed either direction. 1-2 slider is different from the S5-42 with the same improvements as the others but is directional as it must fit inside the granny first gear.
Overall from a first test drive I'd say the S5-47 is absolutely worthwhile over a S5-42. I'm glad I ended up with this core to build rather than going through the S5-42 that grenaded. That being said I'll likely get the new hard parts to fix the old transmission and go through it again. Probably list it for sale for more than a clapped out used trans and less than a big shop rebuild and see if it sells. I've accumulated enough ZF5 parts I'm debating whether I should start building these on the side.
