rgpressler@suddenlink.net Posted July 30, 2015 Share Posted July 30, 2015 Moses, I have read all posts on ax15 transmission rebuild, problems and rented the video. I have pulled the tyranny 3 times replacing seals, bearings, syncros , keys and springs. I replaced the 3rd and 4th syncros which came in my rebuild kit with the straight as opposed to the angled syncros. I am stumped as to why it will not stay in 3rd gear. 1st, 2nd, 4th, 5th and reverse all work fine and can now down shift when I couldn't before. The tranny will go into 3rd gear but as soon as any torque is applied it pops out and I am unable to even hold it in gear. I would greatly appreciate any thing you might suggest before I pull the tranny out again. All my gear clearances are with in spec. Thanks, Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted July 31, 2015 Administrators Share Posted July 31, 2015 Hi, Bob...As an overview, the shift lever, fork and sleeve on the synchro hub must move far enough to allow full engagement. Engagement means the sleeve is thoroughly capturing and locking the 3rd/4th gear synchro hub to the 3rd gear's synchro teeth or "dog" teeth. Jumping out of 3rd gear can result from 1) the 3rd gear rocking on the shaft, 2) the sleeve engagement teeth on the gear being damaged, 3) the shift sleeve not centering or engaging the 3rd gear's dog teeth properly or 4) the sleeve and dog teeth either not being fully engaged or not staying engaged when the shift lever is in the 3rd gear position. Some of my immediate concerns would be: 1) Gear rock on the shaft or the shaft not aligned properly. You share that all tolerances are in spec. This must include the input gear's pilot bore condition and the bearing fit between the input/clutch gear pilot bore and the mainshaft's nose. The mainshaft nose must be concentric and proper diameter. This is the critical engagement point between the input gear and the mainshaft. 2) Make sure the main shaft and cluster gear can hold alignment (remain parallel) when the gear sets are in place. Use a tooth contact paste if necessary to test gear tooth engagement during trial fit of parts. 3) A worn crankshaft pilot bearing can allow the input gear to rock or wobble out of center. If wobbling or cocked enough, 3rd gear and the synchro hub can misalign or cock. This will cause the synchro sleeve to partially engage the dog teeth on the 3rd gear. The unit will jump out of third gear. 4) Of course, wear on the inside of the 3rd gear or 3rd gear bearing looseness could allow the 3rd gear itself to rock on the shaft. Synchro hub and/or sleeve wear can also allow the synchro sleeve to rock, sometimes enough to cause jumping out of gear. 5) Clutch/input gear pilot bore (the mainshaft engagement point) wear or input-to-mainshaft pilot bore bearing looseness, or any cause of looseness that will allow the input shaft and mainshaft to flex at the synchro area, could cause the synchro sleeve to disengage with the 3rd gear dog teeth, resulting in "jumping out of gear". 6) Make sure that the 3rd/4th synchro sleeve is facing the correct direction on the synchro hub. If not, this can create partial engagement between the synchro sleeve and the 3rd gear dog teeth. Inspect the synchro hub to sleeve spline fit carefully. Also inspect the gear teeth (3rd gear and the cluster gear's 3rd gear position) for proper engagement. Note signs of any tooth wear or contact pattern issues. 7) Are you sharing that your 1990 AX-15 had the same brass synchro ring teeth engagement design as the new replacement rings? You're not mixing brass ring engagement teeth types, right? In any case, this would actually have more to do with sliding in and out of gear smoothly than jumping out of gear. If all parts align properly and the shift lever can move the fork and sleeve to fully engage the 3rd gear's dog teeth, then the transmission should stay in gear. 8) Input/clutch gear rock that causes the 3rd/4th synchro hub and sleeve to misalign can become exaggerated with acceleration and deceleration under load. Causes of input gear rock can be a worn input gear bearing (which you replaced, right?) or a worn out crankshaft pilot bearing as I mentioned. Since you're pulling the transmission out again (sorry to hear that!), you will have access to the clutch and crankshaft pilot bearing. Check out the condition of the crankshaft pilot bearing and the clutch disk hub splines. 9) If you suspect that the 3rd/4th gear synchro sleeve is not engaging the 3rd gear dog teeth completely, check the shift linkage, the shift forks and sleeve fork groove for wear and fit-up. Check for shift throw interference. (Even the shift boot, floor pan or carpet can interfere with full movement of the lever.) One issue is a lift kit with a tilted skid plate that angles the transmission in such a way that the shifter cannot move full throw. Make sure the lever moves far enough, and at the end of the lever throw, the synchro sleeve must fully engage the 3rd gear dog teeth. Let's work through this. Check out the shift lever linkage and shift throw before pulling the transmission...If you do disassemble the transmission, please confirm findings or share photos of parts in question, including new versus original synchro rings. Rings need to be compatible with the clutch hub's sleeve design. Compare the inside splines of the sleeve with the hub splines, and this will make sense. You want to find a very specific cause this time around. There always is one... Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted July 31, 2015 Author Share Posted July 31, 2015 I want to first thank you for your extensive reply. I am going to double check my shifter clearance and replace the crank shaft pilot bearing (neglected to do). My kit came with front and rear seals, main bearings, syncro rings and input shaft pilot bearing. The pictures are of the old 1&2, 3&4 and the kit 3&4 syncros. The last tear down I replaced the kit 3&4 syncros with ones that matched the old 3&4 snycros. The clearances I speak of are the clearances between first gear thrust washer .005 second gear & flange .006 and third gear & flange .007. The pictures of the gear assembly are of different angles as I was comparing them with the video pictures. I think the syncro sleeve and hub are on correct?? I will be checking all the things you mentioned when I pull the transmission out and tear it apart again. Starting today. Thanks Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 1, 2015 Administrators Share Posted August 1, 2015 Bob...End play specs are okay. 0.007" on the 3rd gear to flange is in the clearance middle (range 0.004"-0.010"). Your 3rd/4th synchro sleeve faces correctly... Recall from the how-to video that the synchro hub, springs and keys must position and orient properly. The 180-degrees apart spring indexing is crucial to keeping uniform tension on the synchro keys. This is a very important step, as the keys tension the sleeve in all three positions: 3rd gear, neutral and 4th gear. This tension helps hold the synchro sleeve "in gear". Keys and spring tension are important. Abnormal wear is usually obvious on the springs and keys. If in doubt, install new keys and springs. You can bench test the sleeve and spring tension with the input and mainshaft gears in place. Before installing the gear sets into the case, from the vantage of approximately 1:04:03 of the video, carefully slide the 3rd/4th sleeve to all three positions (only within its normal range and without dislodging the keys). You should feel reasonable resistance from the keys and springs in each position. Also review from 52 minutes to 54:20 minutes of the AX-15 rebuild Vimeo-On-Demand video. If you have run out of your 30 day rental period, send me a message through the forums. I'll extend your rental. Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 4, 2015 Author Share Posted August 4, 2015 Moses, I'm Back. I have done a lot of measurements and checking. The first thing, I put the shift housing and shift lever on, held together with clamps. I supported the gear assemblies and observed the operation of the shift forks and synchronizer sleeve. In forth gear the sleeve engages all but 1/16th inch of the cogs and when in 3rd gear the sleeve engages all but 3/32nds inch of the cogs. At that point the 3&4 shift rail snap ring is up against the intermediate plate. The shift fork-to-sleeve clearance for 1&2 and 3&4 are both 0.020". I disassembled the gear assembly and took measurements of the shaft. First gear surface 1.534, second gear 1.848, third gear 1.495, the pilot surface 0.983 and the flange is 0.198. All surfaces smooth, no ripples or indentations. The input shaft bore is 1.456 and its pilot surface 0.590, and also both smooth. The syncro ring to gear of all the new syncros is 0.030. I inspected the first, second and third gear bearings, they looked OK but the cage edges felt sharp. So I ordered all three bearings, should be here Friday. I inspected the new keys and springs and found that my placement of the 3&4 insert springs were not as shown in the video, so I corrected the positioning. I tried to measure 3rd gear wobble by putting pressure on the top and bottom of the gear and measuring clearance. I got 0.005 one way and 0.008 the other way. The 3rd gear to flange is 0.008 while holding 3rd gear straight back from the flange. All of the inner gear bores are smooth. I hope the new bearings will take up the wobble.? Oh yea, I installed a new clutch pilot bearing and checked the shifter clearance through the floor board, no problem there. Are there any other things to check before Friday when my parts arrive? Thanks Bob Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 4, 2015 Author Share Posted August 4, 2015 Moses, I forgot to mention that my video rental will end this week. I hope I won't need it but , just in case - a one week extension might help. Thank You Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 5, 2015 Administrators Share Posted August 5, 2015 Hi, Bob...The new bearings should help reduce that gear wobble. Let's be optimistic, the wobble could have caused cocking of the gear. I'm glad that you found the key springs were misaligned at 3rd/4th. This could have caused uneven pressure on the keys, which would limit their ability to detent the synchro sleeve in the gear positions. Since you have time until Friday, play with the hub, keys and syncho sleeve. Note the difference with the springs installed both ways (right and incorrectly). See whether there is a significant difference in the tension/resistance when you slide the synchro sleeve to the 3rd and 4th gear engagement positions. Glad you replaced the pilot bearing, it's a precautionary measure. Out of curiosity, was this transmission rebuilt before your ownership of the vehicle? Or did it seem "original"? Let me know as you get close to the 30-day end of your rental. I'll be glad to extend the rental to help your current situation... Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 5, 2015 Author Share Posted August 5, 2015 Moses, I couldn't really tell if it had been rebuilt before or not. The previous owner had put in a new clutch but the transmission was a mess. Third-fourth synchro keys were in the bottom of the case in pieces and the brass syncros were chewed up. Probably why he replaced the clutch. It just wouldn't shift with out grinding. Thanks, Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 5, 2015 Administrators Share Posted August 5, 2015 Bob...What do the 3rd gear dog teeth look like? If the PO drove with that kind of gear clash, look closely at the dog teeth on the 3rd gear. Show me a picture, we'll make a call here. If okay, no need to replace. If the teeth are damaged and will not allow engagement and good lockup/mate-up with the synchro sleeve, that's an issue...Keep in mind that the sleeve must be able to hold on the dog teeth when in gear. That's what constitutes gear engagement with a synchromesh transmission. Also make certain that all detents and detent springs are working properly and in the correct positions. This is a busy arrangement. The tension on the detents and interlocks are critical to shift rail positioning and hold. I'm not trying to spend your money, if the parts are okay, reuse them and install pieces in their correct positions. Your comment about a shift rail circlip nearly hitting the intermediate plate raises questions. Pay close attention to the shift rails for each position/gear. During assembly, park the video on images that help sort out these parts and their positions...The PO may have worked on this transmission, parts could be out of order. A consideration... Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 6, 2015 Author Share Posted August 6, 2015 Moses, The dog teeth on third gear look worn to me after comparing them to the forth gear dog teeth. I am sending several pictures of third, forth gears and syncro sleeve. If you think the third gear needs replaced, should the syncro sleeve also be replaced at the same time??? Bob Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 6, 2015 Author Share Posted August 6, 2015 Another picture of my syncro sleeve. Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 7, 2015 Administrators Share Posted August 7, 2015 Photos very helpful...You can see the damage to the 3rd gear dog teeth caused when the keys were broken and out of position. When synchro keys break like in this case, and the driver keeps grinding the sleeve into the dog teeth, this is the result. The brass blocking/synchro rings, without the keys stopping them, simply rotate. This makes it very difficult to engage the gears and does not provide sufficient braking action from the brass rings. Also, the rings likely cocked, and if so, the sleeve could not clutch the dog teeth. This can cause a dog tooth wear pattern that creates the "jump out" condition. How much is a new 3rd gear? The sleeve looks okay from the photo angle, but you need to look closely at the sleeve's inner splines for excess wear. The important aspect with the sleeve is that it must thoroughly capture the dog teeth and not have looseness once engaged. Envision why the assembly "jumped out of gear". A picture is forming... Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 7, 2015 Author Share Posted August 7, 2015 Moses, Third gear cost is $137 and the synchro sleeve is $79. I am going to order both just to be safe. I had already put in the new hub because it was damaged. Pulling this transmission and tearing it down 4 times is really wearing me down!! I will let you know when I get it all back together hoping this will fix the problem. Thanks for all your help. Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 7, 2015 Administrators Share Posted August 7, 2015 Bob...Think of the bright side: You're now approaching "expert" level on the AX15 transmission! Bet you'll drive with the synchronizers in mind, too!That's got to be worth something. Glad you're not reusing the 3rd gear or sleeve. The gear's dog teeth are beaten. The synchro sleeve is good insurance and will match fit with the new hub.You're doing the right thing. Careful assembly and sequencing of parts should do it. Do you need an extension on the video rental?Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 8, 2015 Author Share Posted August 8, 2015 Moses, Your right, I have learned a lot about transmissions but don't really want to be an expert. I have never been a "gear jammer" but now I know what happens to transmissions for those that do. I think I can get along with out the video extension since the procedure is now burned in to my memory. Thanks Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 8, 2015 Administrators Share Posted August 8, 2015 Keep us posted...I want this to be a stellar outcome, you deserve it for the effort, Bob. If you get in a glitch and need access to the video, just let me know. Moses Quote Link to comment Share on other sites More sharing options...
rgpressler@suddenlink.net Posted August 22, 2015 Author Share Posted August 22, 2015 Moses Just got the transmission with the new third gear and synchro sleeve installed. Took a test drive and the transmission worked beautifully. When shifting in to third gear I could actually feel it locking into place. With all of the replacement parts I put in it should be good for another 200000 miles. Thanks for all of your help and direction. All I can say after 4 tries is YAHOO!!!! Thanks Bob Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 22, 2015 Administrators Share Posted August 22, 2015 Bob...This is great news! I'm very glad that we were able to narrow down the final issue to this defective 3rd gear! Worth the new part that remedied the trouble...I'm against replacing parts needlessly or on "speculation". We had good reason to expect a cure here. The best part about this is your ability to diagnose trouble and to think "inside" the transmission even when driving. That's what rebuilding a unit can teach. You'll be considerate of this AX15's synchronizers and moving parts. Keep in mind that the brass blocking rings are braking devices. If forced into action (like downshifting when the vehicle speed is too high), the wear and stress to these blocking devices increases. Brass blocking ring wear is at the inside "grooves" of the rings, a design that performs the actual braking action..."Synchronizing" properly is a driving technique, too. Driven with synchronizing in mind, and with proper fluid change intervals, this transmission should last 200K miles or more—and you can credit yourself for that accomplishment! Moses Quote Link to comment Share on other sites More sharing options...
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