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Triumph TR3 - Shifting Patterns for Gearbox
|What's considered a "normal" shifting experience for our gearboxes? When I shift from 1st to 2nd, there is a definite mechanical pause, or catch, between the two gears. In other words, the shifter does not flow smoothly and without interruption from 1st to 2nd. This is repeated on the other gears, but it seems to be more noticeable on these two.
Is this a normal phenomenon? One associated with age? Or is there mechanical malfunction afoot that Don and his fabricated miracle tools could address in short order?
Not that I'm trying to autocross or anything.
Don, being the only one I am aware of who has had the pleasure of driving one of these girls from day one could probably say the best, but any I have had, you have to be very deliberate about the shift pattern. And they don't like being hammered through the gears. You might want to take a look at the wear on the shift leaver where it fits in the selectors as well as the selectors themselves. There are ball and spring assemblies that on each selector shaft that can suffer from wear as well as the shafts themselves. And then you're into the box! Misaligned or bent forks, worn selector shaft sleeves and worn syncro rings (like mine) can all cause difficult shifting. WHAT SAYS YE SIR DON! What is the fresh rebuild like compared to crisp tight new gearbox back in 58? Brian
|But Brian, I have the original gearbox in my TR3A. Bill has a TR4 in his TR3A. I agree with most of your comments especially about the bal detents.
I made the fixtures and used a fish scale to measure that the axial release force was within spec as required in all the TR Manuals under "Gearbox".
After its rebuild, my gearbox shifts like new, but after 46 years, the memory starts to suffer a bit from "Alka-Seltzer" disease - OH I always forget the real name - so it's getting to me too !
Bill to shift into first when I see that the light is going to go GREEN, I snick it into 2nd gear gate for a second, then snap it into 1st gear. That's because I have no synchromesh in first gear. With your TR4 gearbox, it might not need this. After I accelerate in 1st gear I use two fingers (the 1st & 2nd fingers) straight down and tight together over the knob to flick it right back into 2nd gear. There is no stoppage or pause. Never had this as you describe.
When I'm ready to go to 3rd, I use all five fingers straight down over the top of the knob to click it forward, cross the neutral gate, then up into 3rd. I see so many TR drivers shifting here by holding the knob all around like a baseball bat and then they try to shift on a straight line at a 45 degree angle (straight into 3rd) thinking that will get them into 3rd gear faster ? It's a cleaner shift if one remembers that there is a neutral cross gate in this motion.
From 3rd to 4th, I use the same fingers and straight back action as for 1st gear to 2nd.
There are spring loaded ball detents on all 4 gears in a TR4 gearbox. Plus there are release forces for the shifter rods that must be measured. The screws for these ball detends are settable and are accessible after removing the top cover. On Saturday, I measured these release forces just before I put the top shifter cover back on the gearbox. Check the manual for this.
You mght want ot ask this question on the TR4 BBS site as well as on the British TR Register BBS Forum for TR4.
Hope this helps.
|Bill - After some thought about the hesitations or resistance stops you have when shifting, I propose the following suggestion. Try to shift as I suggested above. If you still have these hesitations, try to note if you get only one hesitation - or do you get two hesitations between 1st gear to 2nd gear, and the same for the others as well.
If you do, I think the person who last rebuilt your TR4 gearbox did not use the measuring fish-scale and fixtures to read the values to set the detent axial release forces. Perhaps he put in new springs. If they were, and still are, too stiff and had he measured the axial release forces for each gear, maybe he would have measured - say 40 or 50 pounds as the axial release forces when the book for my TR3A calls for 25 to 27 lbs for 2nd gear and a release force for 17 to 22 lbs release force for third and fourth. For an all synchro TR4 gearbox, you would also have a spec for your 1st gear.
I just put in new springs in the TR3A gearbox I'm doing for a fellow Montreal TR member and measured very high axial release values, in the order of 45 pounds. So I ground a turn off one end of each spring, one at a time to shorten them and make them weaker, reassembled the springs and balls and re-measured the axial release force - till I was down within the force range of the spec in the re-build manual for my TR3A. It took a while but I finally got it within range. I learned this when I did my own gearbox last week. And mine is shifting nicely.
If the springs for the ball detents are too stiff or too long or both, you may be getting axial release forces of say 40 to 50 lbs. To release out of 1st gear you would move the gearstick to neutral, would get a hestitation putting it into neutral where the springs (too strong) would give you resistance to get there. Then I think you may get a second hesitation as the sliding yoke pulls the gear ring for 1st and 2nd gear into 2nd gear. Or you may only have one hesitation as you have to pull the gearstick very hard to overcome the very high axial release forces between gears.
This is just a longer description of what Brian is saying above. But if, as he adds, the springs have become weakened, these shifts would have a very low axial release force and shifting would get to be "as smooth as silk" with no hesitation or resistance. I believe that the range specified is to give you some resistance, but not too much. I think the resistance is to keep a gear that is not the one you are in from moving forward or rearward. If you were in - say 4th gear, you would not want, say 2nd gear with too weak springs have the synchro ring, then the outer gear ring, engage with the dog teeth on 2nd gear, in which case you would be driving in 4th and almost in 2nd gear at the same time. No-one would want that.
|Maybe I'm lucky or just used to the way they behave. But I've had no real pause or catch between any of the gears. This is experience from 3 TR3's with 3 synchro boxes and now about 3 years with a TR4 all synchro unit with a weak 2nd gear sychro. The 4 is tricky to shift up, there's a rhythm that is becoming almost second nature (no pun intended) to matching speeds while the engine's slowing down between 1st and 2nd. It never grinds, just feels better when it's right. Shifting down to 2nd is much more of a trick, especially if you want to really use engine braking in and high revs out of the turn. If you don't get it right, there will be clashing of gears (grind a pound for me). Even 1st gear will go in at pretty much any sensible speed, but there is that sweet spot just before you come to a stop when the engine's idling.
This may not have anything to do with what you're feeling. The top cover should come off and all the things mentioned in previous posts inspected if you think it's irritating. In general, the more time you take between shifts, the smoother things will go. But sometimes I just don't care, I'll jam it into second, graunch or not. Usually I baby it. I must not want to do transmission work if I've lived with a worn synchro for 3 years..hasn't gotten any worse..
I don't think they ever shifted like a Toyota.
|Bill - Read the S-T Maual with the section for "GEARBOX". If you buy a fish-scale ($5.00 at any shop that sells fishing rods etc.) you hook one end around the gearstick knob. With the engine off and in 1st gear, pull on the other end of the fish scale. You will get a reading. Compare it to the specs in the manual in the area for re-assembly of the gearbox & top cover. Then do all the other gears plus reverse to "Pull it out of each gear". That will tell you a lot.
|Don and Tom,
Thanks for the incredibly helpful detail. Of all the systems on the car, the gearbox holds the most secrets and mysteries for me. It was a revelation just to remove the gearbox from the car. Now I have to go inside?
Let's do it.
I have concurrent issues with the whole shifting experience. At times, I have difficulty getting into first gear from neutral (spinning), and I can have difficulty getting into reverse (spinning). Not always, but more frequently. When I had the gearbox out, I did notice wear on the clutch fork pins, as well some wear on the clutch fingers. I'm guessing this wear adds up to an incomplete disengagement of the clutch. I'm confident about all the settings and functioning of the hydraulic system, so that leaves the pins and fingers. Other possible gremlins?
Given all that, I've always had the "catch" between gears, most noticeably 1st and 2nd. Don: is it possible for me to fool with the detent springs with my fish scale without having to dig too far into the gearbox? If so, I might yank (no pun intended) out the gearbox one weekend, replace the clutch fork pins (can these be rotated to put a better face on the work?) and get my fishing scale engaged with the springs.
One of the joys of working on these TRs is getting up close and personal with automotive subsystems that you understood conceptually, if vaguely, but once you've worked on them, you know for sure. I love it.
|First off, buy the fish-scale and calibrate it. Attach one end to you vice or similat and hank known weights on the bottom end where the fish normally goes. I used sand in strong plastic bags. A true ^# of sand indicated 8# on the scale of the fish-scale. Yhen 10# of sand then 16 #, then 25# and so on.
Next I'd put one end of your fish-scale on the knob horizontally and pull it to get a reading for the total release force for each gear. Compare it to the specs for a TR4 gearbox in the book. This knob pull and/or release force is the sum of the axial release force where your shifter yoke moves the outer gear ring out of neutral into say 1st gear, plus the oil viscosity or resistance plus the force to push back the ball detent that is in the groove where the round shifter rod is held in neutral and going into 1st gear. This is in the top cover ass'y.
I'm not sure of what you mean by spinning. Maybe your idle is too fast. If the synchro rings are worn or it someone used 4 rings (for a TR4 gearbox) from the batch of bad rings (it has been suggested that about 10,000 of these were made and sold - and they didn't work at all if they measured less than 0.410" with a micrometer or vernier to measure this dimension, and later many gearboxes needed to be re-built right away using correct synchros.
To get this right I have re-copied the following from the TR6 group for this BBS written by Brent Kiser, President of the Minnesota Triumphs. The BBS Archives on this subject have been deleted or lost.
"There are or were bad synchro rings being sold by almost every supplier over the last few years. The synchro rings are too thin. Others say they are too short or not high enough.
Synchro rings have 6 tangs sticking out axially. Three of these tangs are rather large (long or tall) and these are there to lock the synchro ring into the shifting hub. When the shifting hub rotates, these long high tangs force the synchro ring to rotate at the same rotational speed.
The three smaller (lower or shorter) tangs are the problem. It the thickness measurement of these lower (shorter or smaller) tangs is less than 0.410", the shifting hub hits the mating teeth before the synchro ring. I can definitely tell you that if your synchros measure less than 0.410", you are most likely to have problems.
The synchro ring is supposed to get the shifting hub and the gear rotating at the same speed before the shifting hub comes into contact with the mating teeth. If the syncro ring is too thin (too low or too short - all the same thing), it either does not hit the gear or it hits the gear too late and cannot get the speeds to match at the same time.
In recent years, I have been re-using old synchro rings that had a good height because all the aftermatket ones were undersize and so bad. But this year I have been able to start buying new ones from parts suppliers that have sourced good synchro rings. If you see a good one next a bad one, the difference is obvious. The thicker (correct ones) measure between 0.445 to 0.470" for the correct axial height of these 3 tangs.
Good luck and I hope thin synchro rings are not your problem.
Brent Kiser "
Don again - The ones I just put into my re-build all measure 0.445" for this important dimension. It shifts beautifully. I'm not sure but it seems logical that old worn synchro rings may have been OK for say 10 years but now have become worn where this dimension has fallen below 0.410". This may be causing Bill and Tom's problems.
If you are planning to change other parts as well, change the spigot pilot bushing in the end of the crankshaft. Mine had a lot of wear in the inside diameter - I'd estimate 0.010" to 0.020" which made the input shaft to my gearbox wobble at the front end. I suspect this wobble couldn't keep the chutch splines close enough to the true center. To get the old pilot bushing out, you remove the clutch pressure plate and the lining, then using a crowbar, force off the flywheel. Put a large piece of plywood and/or carpet on the floor below so that when the flywheel falls, it won't get damaged. Make sure you put the clutch lining back in the correct way. One side should read "This side towards towards the flywheel".
The pins can be rotated on the fork or yoke but I just bought 2 new ones for $4.00. You can rotate them but make sure you re-stake them in with a centerpunch and a heavy hammer so they don't rotate back to the flat or wear spot. You stake in new ones too.
Bill you can pull off the top shifter assembly and check the pull force for the ball detents at the rear on the top. There are three, one for each shifting shaft. But to check to ball detents in the shifting hubs or outer rings, you need to get everything apart.
If you really want to do this yourself, you can get help right here, or I can ask the three or four experts I know for the answers. You will need the thick red book as a reference. I have photocopied the entire section for "Gearbox" to keep my red book free of greasy thumb prints.
But don't start yet. You can't do this in a weekend. It took me a month. In the meantime, I ran TRusty with my spare non overdrive gearbox. Wait for the winter. In the meantime, read all you can about TR gearboxes.
Thanks, again, for terrific help on this.
Perhaps like others with non-overdrive gearboxes, I've been thinking about getting one. This might be the right time. I'd appreciate your advice on finding a good quality full-synchro overdrive tranmission that has been competently rebuilt, or getting one and then having it rebuilt. I'm not sure I want to practice on it.
So...rather than overhaul the one I have now, this could be the time to add overdrive. Given that I love long-distance travel with the TR, I could certainly benefit from it.
I hear you on the time required for the fish scale adjustments. I'm thinking the dead of winter for the overhaul sounds good. Perhaps for the clutch work, too.
Glad to hear TRusty is still on the road, Don. Any big trips left for this season?
|Louise and I are going to become grandparents for the first time. Our son and his lovely Dasha who live in Ottawa (120 miles away) have a possible delivery date on early October for twin girls. So Louise says she wants to stay home so that when it happens we can get there in 2 hours.
I tried to explain that from Cape Cod, it would be about 8 hours and we could still go and be back in plenty of time. So, as for trips, it looks like they are on hold, especially with twins who always arrive earlier.
If the babies are here before Sept 19th, I hope to drive to Toronto and then Oakville to the Toronto TR Club British Car Day held at Bronte Creek Park west of Oakville and east of Burlington (Burloak Drive just off the QEW - "Queen Elizabeth Way"). Entry is $15.00 at the gate, participants choice voting and over 1250 LBC's last September. Maybe I'll be there.
When I was at Gaydon, England at the end of May, I saw a TR3A overdrive gearbox that had just sold for £350.00.
|If anyone finds a TR4 gearbox with overdrive, you must be careful to ask :-
1. Is the overdrive that is attached for or from a TR ?
2. Is it an "A" type (TR2 to TR4) or a "J" type (TR250 or TR6) ?
3. Is the overdrive from a sedan ? There are many Laycock-deNormanville overdrives sitting in scrap yards in or out of Volvos. These would most likely be the "J" type.
By buying a TR4 overdrive mainshaft for about $250.00 (only a few of these left available from specialists), the Volvo O/D can be adapted to the TR4 gearbox. Then you install it, connect the speedo cable and find out that the speed is about 50% off because the gearing in the rear of the Volvo O/D was matched to a Volvo speedometer and there is a difference in the number of teeth for the speedo drive cable.
Buyer beware. I don't know if other drive gears to get the correct speedo ratio are available or if they fit.
If it is a "J" type O/D, you will need to put in the rear tranny support from a TR6 which is different for a TR6 than for a TR3 or a TR4 with "A" type O/D.
|Bill, on the other possible gremlins front:
The main gremlin seems to be the tapered pin (not really tapered?) that holds the clutch fork on the shaft. I don't think I've ever snapped one, but it sounds like it's a common occurrence. The travel of your hydraulics will no longer be enough to fully release the clutch. This will cause grinding into reverse if you're not quick from, say, 2nd. And synchros will wear too much. I suspect this may be the case with my TR4, as well as some overzealous downshifting at some point in its life. But you never know what previous owners have done until it's all apart. My slave rod appeared to have been shortened by grinding, no idea why. Brilliant lazy fix: put an old socket over the end of the rod to extend it. Maybe some day I'll compare all my spares to that one and either use one of those that's longer or cut the end off a bolt and make my own. Or replace the tapered pin if I ever get around to pulling the tranny.
Not having any lube, or dirty old sticky grease on the splines of the input shaft would make it hard for the clutch disk to move away from the flywheel enough to fully isolate it from making the input shaft turn, especially when the tranny is in neutral. In other words, clutch pedal in, tranny in neutral (the bushing Don mentions is touching the shaft inside the crank end too), gears are still turning. The synchros are the first thing to touch when you try to put it in gear, unless you're going to reverse (no synchro). The synchros get the engine and tranny spinning together without grinding gears, and you can feel (and hear in neutral with older bearings like mine)it when they start to do the job. I think this pause or catch is what you're feeling. Again, sorry if this is overly simplified.
That's really an informative article, Don. I hope I'm 60ish before I have to rebuild a tranny. The reason I mentioned Toyota is I did rebuild (with help) a '78 Toyota truck tranny. The problem was a splined shaft that seemed like an afterthought for the overdrive gear only. All others still worked fine. Parts alone were approx. $500 in 1980. Used grease and a bolt and hammer to remove the pilot bearing.
|Toom - I have no excuses when it comes to stupid thind the previos owner did to my TR3A. He is me !
The reason someone could have shortened the output actuating shaft coming out of the clutch slave cylinder is id he re-installed it on the rear side of the flange in the bell-housing. It would suddenly apper tha is is now about 1/2" too long. The books are not clear on this.
The "previous owner" did this on mine when I was much younger, but it's a lot easier to remove and get back on with that long rod that suppoerts it from the 2nd oil pan bolt up front.
Herman van den Akker sells a very smart 5-speed Toyota conversion for TR's.
I'm curious about the lubrication needed on the gearbox input shaft. My understanding upon asking is that the shaft should be left dry, or perhaps with just a bit of dry graphite. I left mine supposedly clean and dry. Could the splines be binding against the clutch friction plate? Hmm...
From what I can tell, it makes no difference if the clutch slave rod is short or long, as long as it's adjusted for proper play.
With my gearbox out of the car in July, I was able to confirm that the fork taper bolt was firmly in place and there was no play between the fork and shaft. I followed the common advice to install a second locking bolt through the fork and shaft. Seems pretty tight to me.
Now you have me wondering about that output shaft lubrication...
Thanks for all the help. This is quite the thread.
|I sometimes get (or leave) a bit of white lithium grease om the splines that mate into the splines of the clutch lining but that's only accidentally. I always put some of this white lithium grease on the front slide for the throw out bearing as well as apply it liberally to the inside of the bronze sleeve that carries the throw out bearing.
|I've also seen a description of a more precision way to offer up the tranny to the block, using guide pins of a closer diameter to the mounting holes. Any offcenter mounting would seem to bind the input shaft a bit in the crank bush, making it harder to put in gear from a stop. Not much probably, but it's something to think about on the next tranny install.
|Bill - If you pull the tranny again sometime, check when it all assembled that the 2 pins at the top of the yoke or fork have enough lateral space that the end of 1 of the pins is not in constant contact with the groove in the bronze sleeve that moves the throw out bearing forward.
I just bought a new clutch cross shaft and put it in, only to discover that the hole in the new cross shaft for the new tapered lock pin was drilled about 1/8" off center so, on one side the pin that moves the sleeve had more than 1/8" end clearance while the end of the other top pin was scrubbing in the root of the bronze groove.
Took it all apart, ground about 1/16" off the rubbing pin and now it's OK.
This thread was discussed between 23/08/2004 and 26/08/2004
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