I_am_a_replicant Posted July 19, 2005 Author Share Posted July 19, 2005 indeed. your right. Hence, the long talk with the dealer before they wrench on it at all. 'Preciate the input. Link to comment Share on other sites More sharing options...
rao Posted July 19, 2005 Share Posted July 19, 2005 First, go to antoher dealer, these guys are clueless. Also, back up one second. The actual gears in the transmission are all engaged ALL OF THE TIME, it is not like the gears themselves move laterally. What happens is that the selector is moved to engage the gear to the driven shaft. http://auto.howstuffworks.com/transmission3.htm Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
melayout Posted July 19, 2005 Share Posted July 19, 2005 if that's the case, then why is it necessary to rev match perfectly in a car w/ dog gears otherwise, you'll either grind the shi+ out of them? helical gears w/ synchros are the easiset to engage which is why they are in all passenger cars (at least i thought that's why) dR The forward helical gears in a manual transmission are engaged 24/7 with the layshaft. The advantage of helical gears is that the angled teeth provide better load distribution than the straight cut teeth on a dog/spur gear. The gear lever moves the shift fork selector which actuates a specific collar gear depending on the gear range. The collar gear then engages with .... oh just read this http://auto.howstuffworks.com/transmission4.htm . Edit - Damnit rao Damnit, grumble postwhore grumble I keed I keeed Link to comment Share on other sites More sharing options...
Xenonk Posted July 19, 2005 Share Posted July 19, 2005 well, just make sure you come to a complete stop when getting in and out of reverse gear.. that little bit of coasting at 2mph or so backing up and moving forward or vice versa can really beat on the gear... And no, there shouldnt be a synchro for the reverse gear (it's only a single gear that goes backwards, what is there to syncronize with?!? Neutral?!? ). Keefe Keefe Link to comment Share on other sites More sharing options...
th7957 Posted July 19, 2005 Share Posted July 19, 2005 Actually Synchro reverse setups do exist out there. The later model NV4500s have a synchro reverse, and so do some mazda(ford) transmissions. I could have sworn that I read somewhere the the leg and lgt were fully synchronized in all gears forward and reverse, but now I can't seem find it. Maybe I was on some bad crack that day. Link to comment Share on other sites More sharing options...
AWDpower Posted July 19, 2005 Share Posted July 19, 2005 Helical gears are used for forward gears because they are quieter. Straight cut gears are stronger, but much louder. Many race cars use straight cut gears, that's why you hear that loud whine, louder then the engine. Jason K. Link to comment Share on other sites More sharing options...
S4 Posted July 19, 2005 Share Posted July 19, 2005 The Cobalt SS has a reverse synchro. It's also fastar than an SRT-4. Link to comment Share on other sites More sharing options...
EJ20Legacy Posted July 19, 2005 Share Posted July 19, 2005 Your mechanic is an idiot. There is no synchro on reverse. Reverse is a straight-cut gear as opposed to all of the other gears, which are helical cut. Reverse is noisy because of this. However, if it's making ratcheting-type noises there is probably something wrong. Reverse is a very thin gear so maybe it has been damaged. Pop the clutch under power in reverse and you can very easily break it. You may have a missing tooth on the gear... (which would actually cause a ratcheting noise) If you want to check for that kind of damage yourself, drain the fluid. Look on the drain plug for metal chunks and obviously look in the fluid for anything (magnet on a stick might help). The advantage of helical gears is that the angled teeth provide better load distribution than the straight cut teeth on a dog/spur gear. This is very not true... as was some of the other things mentioned in other posts (like being harder to engage, which is completely false). The ONLY reason passenger cars have helical cut (teeth go at an angle across the gear) gears is because they are quiet. They provide worse load distribution than straight-cut gears because they produce side loads thanks to being angled. Straight-cut gears are much stronger simply because they do no produce loads at any sort of angle and the teeth can usually be thicker. This not only makes the gear stronger, but the transmission and shafts as well since they don't have to support these side loads. Straight cut does not mean dog gear. You can have a full synchro transmission with straight-cut gears. The method of gear selection has nothing to do with the type of gear. As mentioned previously here, the gears are ALWAYS meshed. It is the selector that you feel engaging and it is the dogs (all trannies have dogs. They are the teeth on the selectors) on the selector that you hear grind when you grind your 'gears.' Reverse is straight-cut for two reasons: 1) it is a very (very) narrow gear in order to fit into the transmission. It truly has to be straight cut for strength, and it's still easy to break 2) reverse noise doesn't matter, you're only in it for a couple seconds a couple times a day. Hope that helps a bit. Jeremy Link to comment Share on other sites More sharing options...
EJ20Legacy Posted July 19, 2005 Share Posted July 19, 2005 Hey here's a fun picture for ya'll From right to left: 1st gear, straight cut. Reverse (small top gear is part of the PPG set. Large bottom one is the stock reverse gear) 2nd gear, straight cut. 3rd gear helical 4th gear helical ...outside of the case where you can barely see on the left edge is 5th, stock... This is a synchro tranny on all gears (except reverse, of course ) http://www.wrxfanatics.com/uploads/post-13-1108733448.jpg Jeremy Link to comment Share on other sites More sharing options...
melayout Posted July 19, 2005 Share Posted July 19, 2005 This is very not true... as was some of the other things mentioned in other posts (like being harder to engage, which is completely false). The ONLY reason passenger cars have helical cut (teeth go at an angle across the gear) gears is because they are quiet. They provide worse load distribution than straight-cut gears because they produce side loads thanks to being angled. Straight-cut gears are much stronger simply because they do no produce loads at any sort of angle and the teeth can usually be thicker. This not only makes the gear stronger, but the transmission and shafts as well since they don't have to support these side loads. Hope that helps a bit. Jeremy From the http://auto.howstuffworks.com/question522.htm : This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears. Also, because of the angle of the gear teeth, more teeth are in engagement at any one time, this spreads the load out more, and reduces stresses. Each time a gear tooth engages on a spur gear, the teeth collide instead of gently sliding into contact as they do on helical gears. This impact makes a lot of noise and also increases the stresses on the gear teeth. When you hear a loud, whirring noise from your car in reverse, what you are hearing is the sound of the spur gear teeth clacking against one another! Is the article incorrect ? I keed I keeed Link to comment Share on other sites More sharing options...
gfxdave99 Posted July 19, 2005 Share Posted July 19, 2005 My Cadillac CTS 5MT had a reverse synchro (for the record) If everything seems under control, you're just not going fast enough. - Mario Andretti Link to comment Share on other sites More sharing options...
th7957 Posted July 19, 2005 Share Posted July 19, 2005 EJ20Legacy: Pardon my curiosity, I can't tell from the picture, is the reverse countershaft gear attached to the 1st/2nd synchro sleeve? If the sleeve or 1st/2nd synchro ring was broken, the noise should manifest itself in 1st or 2nd, as well as reverse. Link to comment Share on other sites More sharing options...
Ridgeracer Posted July 19, 2005 Share Posted July 19, 2005 Hey here's a fun picture for ya'll From right to left: 1st gear, straight cut. Reverse (small top gear is part of the PPG set. Large bottom one is the stock reverse gear) 2nd gear, straight cut. 3rd gear helical 4th gear helical ...outside of the case where you can barely see on the left edge is 5th, stock... This is a synchro tranny on all gears (except reverse, of course ) http://www.wrxfanatics.com/uploads/post-13-1108733448.jpg Jeremy Thanks for the info. My friend thought something was wrong with my car when he heard gear whine in second but I didn't know at the time our 5MTs have straight cut gears for first and second. "Gimme mines Balboa...Gimme mines".....Clubber Lang - Mr. T Link to comment Share on other sites More sharing options...
RobY Posted July 19, 2005 Share Posted July 19, 2005 The Cobalt SS has a reverse synchro. It's also fastar than an SRT-4. Nothing is fastar than an SRT-4 not even a lamans racecar Link to comment Share on other sites More sharing options...
RobY Posted July 19, 2005 Share Posted July 19, 2005 From the http://auto.howstuffworks.com/question522.htm : Is the article incorrect ? Very very very incorrect the guy should be shot... Gears stay meshed all the time. Its the selector collar that gets knocked around.... Thats like transmission 101 LOL. Link to comment Share on other sites More sharing options...
th7957 Posted July 19, 2005 Share Posted July 19, 2005 I've seen an SRT-4 break the sound barrier with 4 flat tires Link to comment Share on other sites More sharing options...
ken_depew Posted July 19, 2005 Share Posted July 19, 2005 My car when i shift from 2nd to 3rd it grinds with clutch full engaged. Link to comment Share on other sites More sharing options...
gfxdave99 Posted July 19, 2005 Share Posted July 19, 2005 My car when i shift from 2nd to 3rd it grinds with clutch full engaged. Maybe you should lay off on those 5K rpm launches :lol: If everything seems under control, you're just not going fast enough. - Mario Andretti Link to comment Share on other sites More sharing options...
dark_rex Posted July 19, 2005 Share Posted July 19, 2005 The forward helical gears in a manual transmission are engaged 24/7 with the layshaft. The advantage of helical gears is that the angled teeth provide better load distribution than the straight cut teeth on a dog/spur gear. The gear lever moves the shift fork selector which actuates a specific collar gear depending on the gear range. The collar gear then engages with .... oh just read this http://auto.howstuffworks.com/transmission4.htm . Edit - Damnit rao Damnit, grumble postwhore grumble :confused:that's all fine and good, but it doesn't respond to my question at all. thanks for the linke but i know how a ManTranny works. lol Engaging helical gears is easier b/c they are angled and slide into eachother, rather than contact eachother head on. this is why your reverse gear "whines" the only advantage I know of to helical gears is noise. dog gears are stronger, and can support more horsepower all things being equal. as for "better load distribution" i'm really not sure what you mean. i guess maybe you've got more teeth in contact at once time... but i'm not sure why that's relevant. What mattes is the strength of each tooth in comparison. dR Link to comment Share on other sites More sharing options...
dark_rex Posted July 19, 2005 Share Posted July 19, 2005 Straight cut does not mean dog gear. You can have a full synchro transmission with straight-cut gears. I know that, but I have honestly never seen a straight cut gear with synchro tranny. have you? otherwise, you're post is dead on. I agree completely, (particularly with the idiot mechanic) although he isn't too far off. the reverse gear is almost certainly a couple teeth shy of a smile. dR Link to comment Share on other sites More sharing options...
S4 Posted August 2, 2005 Share Posted August 2, 2005 Very very very incorrect the guy should be shot... Gears stay meshed all the time. Its the selector collar that gets knocked around.... Thats like transmission 101 LOL. The article says that gears stay meshed all the time and it's the collar that actually engages the gears. I believe that from the quote, they were talking about how the teeth of the gears come into contact with each other. Helical cut gears gradually come into contact with each other as opposed to straight cut. Link to comment Share on other sites More sharing options...
Hutch Posted August 2, 2005 Share Posted August 2, 2005 I just got my 5sp LGT back from the dealer. It was popping out of reverse and it got worse as time went on. I have just over 13,000mi. This is what the invoice said: "car was popping out of reverse due to internal failure. Upon teardown, found reverse drive gear on pinion drive shaft damaged from slipping out as well as reverse idler. Found reverse shift lever to be of improper size causing clearance between idler and case to be incorrect (4mm). Replaced size 9 with standard 8. Also found detent socket in reverse/ 5 shift fork rail worn down. Replaced rail and detent. Replaced reverse idler gear, overhauled pinion drive shaft and replaced reverse drive gear." Some of this is greek to me but it does work now. The ecu was also replaced for the cooling fan being stuck on. I knew I should have went with the Acura. If I wanted these kind of problems with a vehicle, I would have purchased a Chevy. Link to comment Share on other sites More sharing options...
supertech49 Posted April 10, 2007 Share Posted April 10, 2007 Hello all, I'm a service manager at a Subaru dealership, and like to use all resources available to find remedies for problems. After searching for a reverse issue we have here, I think I found the answer I was looking for in Hutch's post. Thank you. I should add that reverse is indeed synchronized in this transmission, which serves to stop the input shaft from spinning to reduce gear clash into reverse. The synchronizer for reverse is shared with the 5th gear. Link to comment Share on other sites More sharing options...
rallispec Posted April 10, 2007 Share Posted April 10, 2007 Hello all, I'm a service manager at a Subaru dealership, and like to use all resources available to find remedies for problems. After searching for a reverse issue we have here, I think I found the answer I was looking for in Hutch's post. Thank you. I should add that reverse is indeed synchronized in this transmission, which serves to stop the input shaft from spinning to reduce gear clash into reverse. The synchronizer for reverse is shared with the 5th gear. interesting.... anyhow - glad you were able to find answers here. Link to comment Share on other sites More sharing options...
700watts Posted April 11, 2007 Share Posted April 11, 2007 i bet this dealer wanted to change the muffler bearings too.... LMAO !!!!!!! Link to comment Share on other sites More sharing options...
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