Not one to start thread but got a issue. Transmission is a 3speed 39' that was rebuilt ~700 miles ago according PO. Pops out of 2/3 gear on deceleration slight grinding on 3rd when shifting quickly. No grinding when I double clutch. Pulled the top of the box expecting to find carnage but only really really low fluid. Took the fluid to work and threw it under a scope, no metal flake. Fluid is clean and new, viscosity feels right. Checked to see if the top plate and shift linkages everything clean. Compared it to a unused linkage that I have and its shape and angles are exactly the same. Can low fluid cause pop out? Wear on all gears is clean.
Hard to say what is causing your tranny to pop out of gear, but I wouldn't expect to see carnage based on your description. I would expect worn synchros or too much play in the system somewhere. I don't think the shift tower is causing the problem. Not a '39 tranny by the way, looks to be '32-35 based on the early synchro hub and straight cut slider (first & reverse) gear. Will Kimble
Irregardless of how long ago you were told it was 'rebuilt', something was missed or skipped and parts may not have been replaced with new.... ------------ Did you notice that if you backed off when in 2nd gear, the gear shift level popped up a bit? That's an indication that there is either too much main shaft end play and/or the 2nd gear snycros are worn out. (slight grinding into 3rd indicats at least worn snycros). Also, worn teeth can cause the gears to run off center of each other and that will eventually cause chipped/broken teeth which will help/cause it to pop out of gear. Mostly it just sounds like your box is getting old and needs some service/attention (irregardless of who said it was rebuilt and when). Normal wear and tear for a 70 year old Ford, that's all. Replacing the 2nd gear synchro assembly, along with the detent (often worn to a funny shape) and it's spring (weak) + eliminating the end shaft play will cure your ails. Go to Vanpelts site for parts and service info. http://www.vanpeltsales.com/FH_web/flathead_home.htm good luck with your box moe .
Had the same problem with a open drive truck 3 speed. It was my pilot bushing... it was all out of shape.
That is the story of every used part. It was just rebuilt. Honest..... No popping up though cannot be sure. I need to pull the whole box to test for end play though. At that point I will do the syncro at a minimu and check everything for proper lash. I have a spare transmission case if that's required and a new main shaft that I checked for spec, its good. Worse case those will go into the car. Thanks for the help guys look like I am going to pull it after the Big three at Qualcom this weekend.
Also, you should really avoid down shifting unless realy necessary, use your brakes and keep them in good order to avoid unnecessary downshifts. here's some service info for your syncros Take note that if your shifter forks are worn, they won't hold the syncros fully in place and that can allow the syncros to wander and it may pop out of gear. Shifter forks are often over looked in the rebuild stage, over time shifter forks can also become sprung. .
Had the same problem some years ago and it was caused by worn shifter forks. Traded them out for another pair that were less worn and the problem went away. If you have another top assy. you may want to try it before pulling the tranny. P.S. If you are going for a major tranny rebuild, it may be worth your while to find a 78 series gearbox and stuff it full of '41-'48 passenger car gears from a side shift transmission. The 78 series box is found in the '37-'39 passenger cars and the '37-'52 pickups. Although Ford introduced their improved gearset in 1939, it was not all inclusive until the '41 model year... But then you'll have a "real '39" transmission...
Yes, and may as well check/replace the detents and springs (contact Mac VanPelt). I also notice that "slight grinding on 3rd when shifting quickly. No grinding when I double clutch. " -These transmissions are not made to be shifted quickly, it adds to the wear of the syncros and can result in chipped teeth (gears) as well as it puts an extra strain on things like shifter forks. Early boxes with straight cut gears (to mid '35) are designed to be shifted with care/slowly. Sometime in mid '35 a switch to helical gears was made as well as the synchronizing drum was updated which aided in shifting. But still, they are not designed to be speed shifted or pushed/forced into gears. I guess it's easy for us all to just jump in and drive the snot outta things just as if it were a new T5/Mustang but due to the age/design of early Ford transmissions, an adjustment of driver attitude and technique is necessary- Avoid downshifts -Avoid speedy forceful shifts and your 80+ year old Ford (Design) will be happier for it. .
I actually have another set of forks. The ones in the car now are a bit smaller -1.0-0.5 mm and have a slight wear angle on the front fork. Guess I can throw them in, fill the box correctly and see what happens. As for shifting quickly its not like I am slamming gears. If I carefully select and feel for the engagement no noise, but if I move in a fluid motion from one gear to the next it grinds. Double clutch at any speed and no grind. Mind you I have a modified Flathead in front of the box and it is way over the 60hp/90hp rating that the box would have so that might be putting a bit of strain on it as well.
It can be the littlest and damndest thing that is causing it. A buddy of mine has a similar problem with an earlier tranny and near replaced all the bits with new stuff to get it right. Till this day he does still not know what he actually did to fix it.
I guess it's a matter of personel choice for many but there are several trains of thought on downshifting. Some I believe in, some I don't. We can all make up our own minds when faced with some points. -Brakes are cheaper to replace than clutch, pilot, throughout bearings, syncros etc. as downshifting places an extra un-needed stress on all things right down to the thrust washers. -A transmission is designed with helical cut gears that place torsional forces on shafts/gears etc in a certain direction, when a reversal of torque is applied (downshifting) the helical gears will apply torsional forces in the opposite direction of what they were designed to be run in. (maybe more true of older trannys) -Most often downshifts are forced into gear without bringing engine rpms to match, placing undo stress on syncros, shifter and shifter forks, bearings etc. -A mismatched rpm/downshift is especially hard on things like output shafts and universal joints. -If you are finding that you are applying extra effort to the gearshift to force the downshift, this 'extra effort' is multiplied many fold onto the shifter forks inside the transmission causing un-needed wear of same. All shifts should be as easily executed as a regular upshift and most downshifts are not. -Allowing an engine to rotate at high rpm without the gas pedal being depressed loads up the exhaust and muffler with unburnt fuel which in turn burn up the exhaust system shorting it's life -There is no advance curve built into the timing to adjust for a high revving engine that has no throttle applied, fuel is not properly quenched inside the cylinders and the wet mixture can and will wash a certain amount of oil from the cylinder walls as it exists unburnt into the exhaust system. (this will become more evident on higher milage cars when downshifting as the start to and tend to burn blue) -Increasing the rpm of the engine from it's ~700 rpm engine idle to ~3000 rpm burns off fuel at a higher rate. 4X the rpm = 4 times the intake stroke of the "idling engine" and fuel consumption goes up. -Many police driver training schools (foreign) teach that downshifting creates an extra element of danger and introduces a certain lack of concentration on the job at hand (catching the bad guys). -Using the brakes applies equal braking to all four wheels lessening the chance of rear wheels skating out form under you. Perhaps this is more evident on wet or slick roads. A famous quote by an Aussie racing champion [Peter Brock], ... "<layer id="google-toolbar-hilite-0" style="background-color: Yellow; color: black;"><layer id="google-toolbar-hilite-0" style="background-color: Yellow; color: black;">GEARS are for GO.....BRAKES are for SLOW</layer></layer>" http://www.jalopyjournal.com/forum/archive/index.php/t-177982.html Another quote: ""Among the more vocal exponents of the don't-downshift school are Tom and Ray Magliozzi, hosts of the radio show Car Talk. These guys admit you should downshift when driving down a long hill; otherwise your brakes heat up so much that the brake fluid boils and you lose your ability to stop the car. But on all other occasions, they argue, downshifting does nothing but wear out your clutch faster. A clutch job is expensive; a brake job is cheap by comparison. The proper way to stop is to rely solely on the brakes. Don't put the car into neutral right away, though. Wait till you get down to 10 or 15 miles per hour or just before the engine starts to lug, then throw in the clutch and shift into second in case you need to accelerate. When you come to a full stop, shift into neutral and release the clutch. "" http://webcache.googleusercontent.c...html&cd=1&hl=en&ct=clnk&source=www.google.com As stated earlier, it's a personnel choice for most people but again, most people are not adept at making a smooth downshift even 5 out of 10 times especially with the older transmissions/designs that our pre 1960 cars come with. I wouldn't hesitate to say that newer transmisions are well adept at downshifting as are engine management systems that can control the amount of fuel of a high revving/idling engine that is not being placed under even a light throttle pressure.
This is pretty much reminding you that your gearing with a '39 toploader. Naturally, they sometimes pop out of 2nd, and sometimes 3rd on de-acceleration. It's the nature of the beast! Also, you'll notice it has no syncro when trying to down shift from 2nd to 1st. That's why I love these boxes and will definitely run it on my AV8 when the time comes.... They've got a character of their own! HC.
^^^Yes, the nature of the beast is that the parts themselves are 70+ years old - as is the design of those parts.
Had a similar problem in a Bel Air years ago. A combination of thinly worn shift forks and an undersized pilot bushing.
@moefuzz; What if you rev match and/or double clutch when you downshift? Does that put less stress on the engine/gearbox?
Keep a check on the forks and the tower...make sure everything is snug at the base...and on the cup. I use a heavy blue tub grease when assembling mine "belray waterproof grease" it helps keeps all the needle bearings in the friggin places...and also seems to run with less play down the line.
On your top cover at the side there are 2 things that look like a screw heads , undo these there will be a spring inside and a ball bearing that holds the shift levers in place on the shaft. These springs and bearings can get worn. I took mine apart over Christmas and one of the springs was broken. You can shim the springs with a washer or 2 to hold them in place tighter. Worth looking at you can do this to see if it cures it without taking the box out and stripping it before you start worrying about duff synchros. There was a guy on Ebay selling a kit of new springs and bearings to do your whole top cover for a few dollars. Rich
He still still sells them, don't know if it will work with a pre 39 top though. I pulled my spare apart last night and no balls or springs so that ones a bust. Hope they are are in there or I am going to feel very foolish.
I just bought a kit from him last night, the add states that it only works in the 39-up towers. If yours has no balls/springs the shifter would be very sloppy...the balls and springs hold it in it's selected gear
Hey, I am still thinking about this thread and want to weigh in one more time... You want your synchronizer to keep the transmission in second or third gear. You want your shift tower to PUT it in second or third gear, not count on it to hold it there. You might make a small improvement if your shift tower is not right. But in my opinion the real problem is too much play somewhere in the input shaft / synchronizer / output shaft. Will Kimble
If you have the early synchronizer i think the brass is made in one piece and not replacable.I don,t know if you can buy them today.When under power 2 nd pushes forward,when letting off the cluster gears pushes 2nd to rear and pull out.All wear adds up.Lot of guys getting rid of these trans and maybe still good parts for yours.
Will for some reason I always think of it as the reverse. The syncro is there to help it into gear and the tower is under tension to hold it there. On a side not since the car is but back together and running..... I was wondering if something is twisting in the transmission during deceleration when there is no load. It does not pop-out under power. Which kind of make sense as there is a lot more load on the gears when you are applying power from the motor. Maybe a misalignment on the main shaft that causes a bit of binding. I am going to send the second transmission out for a complete rebuild just to at least have a backup or to sell. I have checked the casing and its to spec. Also it's a lot smoother now that there is some oil in the box. Shifting pressure is easier. But it leaks a good bit. Hopefully its bearing or the case then maybe I can find the deflection in the box. Only time I have been happy to find a leak on my car.
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