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Posted By Discussion Topic: Sycro problem -- page: 1 2     supereal 10-04-2015 @ 11:57 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 If you are having shift problems, be sure that the clutch free play is between 1 1/4 to 1 1/2 inches, and that the idle speed is about 500 rpm. Also, check the clutch pedal return spring. The pedal must fully return when released, or the clutch plate will not allow the clutch disc to change speed so the gears can change without grinding.. agriffey 10-04-2015 @ 12:06 AM reply profile send p.m. Member Posts: 28 Joined: Sep 2015 Actually the tranny design is the same but the brass synchro rings will wear out after many years of shifting. My '51 F1 has the same tranny as your '47 car but I have to do an Old Henry when I shift into second or high. If I ever have to remove the tranny for clutch or something I will replace them. It is not bothersome enough to worry about. High speed driving and 140 roofing tar will not keep the needle bearings in the cluster gear lubed. Add me to Old Henry's list of 85-90 gear oil users. Plenty of lube is better than a slow short supply. Also there is the cold weather problem. When I was in high school I traded my '40 Ford for a '46 with 40,000 miles on it. The second day I had it I burned the rear end out of it. It had too heavy of gear oil in it. The ring gear just cut a path through the stiff grease. The outside temp was in the minus 30's. 85-90 would have saved it. I should have noticed the first couple of blocks I drove it it felt like the brakes were dragging. Drbrown 09-04-2015 @ 9:45 PM reply profile send p.m. Senior Posts: 588 Joined: Nov 2013 I never paid any attention to whether or not the tranny was heated-up. Regardless, will drain, put 90w in, do the patient shifting, and see how it works .... don't need a tranny rebuild in my job jar unless its real. Offbeat ... I remember late-night drag runs in the late '50s with my '51 merc .... didn't need to hesitate with that. Must have changed the tranny design by then. Thanks to all !! shogun1940 09-04-2015 @ 3:44 PM reply profile send p.m. Member Posts: 464 Joined: Feb 2010 the brass syncro is supposed to lock onto the gear shaft as you are shifting. If it does not then the gears will grind so a lighter oil may help but the real problem is that the syncro needs to be replaced. cliftford 09-04-2015 @ 1:01 PM reply profile send p.m. Senior Posts: 845 Joined: Jan 2014 Hello Drbrown: I put 85/140. wt in my transmission because it was a used but serviceable unit,and I wanted to keep leakage to a minimum. I agree with the others that 90w is probably ideal. The principle of the syncromesh, as I understand it.is to cause the mating gears to spin at the same rpm's so that they engage smoothly Someone correct me if I'm wrong. Too heavy weight oil might hamper this.One supplier sells 600w oil and says it is for 32-48 ford rear ends and transmissions. I was thinking maybe that was what somebody had put in your trans. A way too heavy in my opinion. This message was edited by cliftford on 9-4-15 @ 1:03 PM Stroker 09-04-2015 @ 11:32 AM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 When I was learning to drive dad's 38 in the 50's, I had the same problem. I had already "mastered" double-clutching on the farm trucks, but expected to not have to do this on the 38. Dad said you just have to be patient, and say the "magic word". So..when shifting out of low, you pause in neutral and say: Synchro-Mesh. Sort of like counting one-thousand, two-thousand...works every time! For the 2-3 shift, a very slight pause in neutral would ensure a clean shift. The 32-39 top-loader would let you know if it was unhappy with tactile feedback through the stick. A column shift sort of dampens the transmission's protests. I have noticed that things tend to get worse as the gear oil heats up, so I do believe that viscosity does play a role when stuff is "imperfect". I believe Old Henry has learned to live with imperfection, as have I. This message was edited by Stroker on 9-4-15 @ 11:42 AM Drbrown 09-02-2015 @ 9:39 PM reply profile send p.m. Senior Posts: 588 Joined: Nov 2013 Old Henry and Steve .... Thanks for input. I'll drain the gear oil just to see what comes out. Then replace with the 90w - good since I live in the wintery northeast. Certainly won't hurt to see if any change. Good to hear you two are doing "the pause" going thru neutral. I got use to doing it anyway. (off topic: I'm spoiled by our 2003 VW which has a fabulous manual .... nicely ratio'd, smooth, small shifting pattern, not notchie. If one feathers the gas pedal just right, can shift 2/3/4 without clutch.) PS: If I remove the shifting yoke side panel on the tranny, is it possible to access the spacers to check the clearances with a feeler gauge ? This message was edited by Drbrown on 9-2-15 @ 9:46 PM len47merc 09-02-2015 @ 3:30 PM reply profile send p.m. Senior Posts: 1165 Joined: Oct 2013 Agree with Old Henry - a good pause between second and third and never a problem with the shift. I can make it grind ever-so-slightly on this shift if am more than a bit too quick and/or timing with the clutch pedal versus the stick is slightly off. Driving it like the cruiser it is never have the issue. Btw, consistent with Old Henry I run (85W-)90 in the trans as Henry spec'd it. Mine is the original trans with 41K miles on it. Steve This message was edited by len47merc on 9-2-15 @ 3:34 PM Old Henry 09-02-2015 @ 3:00 PM reply profile send p.m. Senior Posts: 738 Joined: Apr 2010 I think the title to your thread accurately identifies the problem, not the oil viscosity. I use 85W-90 as recommended by Ford in my tranny and haven't had that problem since I rebuilt the tranny and replaced the syncro parts and particularly the spacer (part 7069). I had to put a thicker one in to reduce that critical clearance on that shaft. If the syncro is working right you shouldn't have that problem regardless of oil viscosity. That being said, I still hesitate in neutral a second when shifting just to give the syncro a chance to do its job. This message was edited by Old Henry on 9-2-15 @ 3:02 PM Drbrown 09-02-2015 @ 10:49 AM reply profile send p.m. Senior Posts: 588 Joined: Nov 2013 Thank you cliftford. Have not had the car long and don't know what weight gear oil is in it. Will replace with 140w and hope the issue stops. If not, a complete drive train rebuild may be in-order cause I hear a slight "clunk" sound in the rear end if I let the clutch out rapidly. That especially happens if I accidentally have the BW OD engaged at a traffic light (I know that's a no-no).

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