| Author | Message | ||
     Graham Watson Experienced User Username: graham508 Post Number: 108 Registered: 03-2016 |
Hello all, I was out driving my 1948 MKVI B340DA yesterday and I went down a long hill in 3rd to the bottom of the hill and stopped. I shifted into neutral then I thought into 2nd, when I went to proceed I found I was in 4th and put in the clutch to change into 2nd however, I found that the gear shift lever was jammed and would not move out of 4th gear. I Tried various forms of wiggling and tugging but to no avail. I have yet to inspect the rear transmission mounting rubbers I know they can sometimes degrade and cause issues with reverse gear but can they cause issues with 4th? Any troubleshooting suggestions would be most welcome, as well as tips on how to remove the large amount of floor screws if it comes to that. I have also posted this on the RROC site. Thanks Graham | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 710 Registered: 07-2018 |
If you thought you were in 2nd and it was actually in 4th, how well is the shifting carriage sliding back and forth when it's in neutral ? When in neutral, the return spring should easily push the shifting carriage all the way to the 3rd and 4rth plane, you should not have to hunt for the 4th gear _ or any gear. I'm just sort of guessing here as to what the problem is. If the bearings in the shifting carriage are dry and dirty, that could be jamming it in fourth gear. Some times there can be so much dirt and debris collected in the "gate" area, that can keep the carriage from entering into the 3/4 shifting plane. This in turn can cause the shifting fork inside the trans being stuck between 3 and 4. About the rear torque transmission mounts being worn causing this trouble. I've come across cars where these rubbers are pretty shot to the point where one can freely rock the engine with ones bare hands, and the car still shifts. If your engine is tilted to one side, have someone right the engine straight up and down, and see if it will come out of fourth. Even if it's not tilted, rock the engine back and forth and see if you can get it out of fourth. Honestly though, if those rubbers are healthy, you should not be able to rock the engine at all. No tricks on removing the floor, you just need a lot pf patients and time. Get a good fitting screw driver that fits snuggly into all the pan head screws, I usually get one that's oversized and grind it down to fit where I have to tap it in to fit the slot. The usual, make the slot is clean of rust and dirt so the screw driver fits all the way into the slot. If one or two give trouble, or if it twists off, I take a small torch and heat the capture nut to set it free. I use a Dremel tool here to cut a slot in the twisted screw, or cut it flush, bend back the tabs so I can remove the nut. This enables me to work at getting the screw out on the bench. When I removed my floor, I tapped all the captured nuts out to 1/4 28 and used new stainless pan head screws. I could not find 1/4 26 stainless screws that were the proper pan head screws. Take note, you may also have to remove the front section of the floor where the pedals are as it sits on top of the main floor section. However you may be able to slide the main floor section back without having to remove the front section. I have never tried this as I just removed the entire floor, and was planning to do so. You can work on the shifting carriage and its gate without having to remove the floor. Removing the floor is a huge job and you may be just opening up a can of worms. . | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 711 Registered: 07-2018 |
Here's another post on the subject, but make sure the shifting carriage is working as it should before assuming anything is wrong with the trans. http://au.rrforums.net/forum/messages/16999/43355.html?1666633326 | ||
| Graham Watson Experienced User Username: graham508 Post Number: 109 Registered: 03-2016 |
Many thanks Jeff, I will be checking out the carriage first thing in the morning. | ||
| ChristopherCarnley Unregistered guest Posted From: 109.156.183.33 |
It could be that the third speed thrust washer has fragmented and is jamming the the synchro sliding piece. This "Achilles heel" of the fragile, hard steel .175" thick washer was never fully strengthened by the .275" washer until 1954, although there was service modified arrangement of .225" in 1952. Without dismantling the unit there is no cure. (Message approved by david_gore) | ||
| Graham Watson Experienced User Username: graham508 Post Number: 110 Registered: 03-2016 |
I removed the shift boot and checked the carriage area. I found a piece of foam rubber wedged in the gate at the 2nd and 4th position area. How it got there I have not a clue as it does not match anything else on the car. I removed it but no joy still stuck in 4th gear. I tried to rock the engine and it would not budge. I looked at the rear transmission mount and it was bulged a bit but it did not look bad. The fore and aft transmission stay rod and rubbers looked in good shape. I am next going to remove the transmission top inspection plate to see what I find. Waiting on new transmission mount to arrive will put it in to be on the safe side. In a perhaps unrelated issue once the car was off the ground I noticed that the left front wheel was locked up. When it rains it pours. | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 712 Registered: 07-2018 |
If the engine is solid and won't rock, that's a good thing. Changing the rear mount isn't going to help your problem, unless it's very rotten. The gate housing on these cars are mounted to the frame and that in turn is shimmed so the shifting fork inside the transmission moves freely across the shifting rods in the trans. If this become out of alignment, difficulty shifting and jamming can occur. If the shift lever in the car moves freely across its travel while in neutral, then the problem lies inside the trans. Assuming that it moved freely before it got jammed in 4th. If you have determined that the problem does not lie with the shifting gate, not lining up to the rods with in the trans, then Chris's post comes into play. Start with the simplest and eliminate on down. Here's a post that talks about that thrust washer. It's not a complex transmission with its simple synchro cones, but the whole thing is like a Chinese puzzle that only comes apart and assembles in one way. Although I did have my own way of re-assembly, I found it easier then what the manual said. http://au.rrforums.net/forum/messages/16999/41017.html?1661678835 You can drain the trans, and remove the big side cover to inspect things with out having to remove the trans or the floor. If it's what Chris says it is, it's a good winter job in a heated garage. I did initially remove my trans with the floor in place, but it was a BITCH. I opted to remove it to make the mounting much easier _ cleaned and painted everything too. . | ||
| Graham Watson Experienced User Username: graham508 Post Number: 111 Registered: 03-2016 |
Thanks Jeff, The shifter has almost zero movement right now. I Will give the gate a closer inspection. Thanks | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 713 Registered: 07-2018 |
Sounds like a problem inside the trans as mentioned. If you remove the gate from the frame to confirm its proper working (and you can), that leaves the shifting fork that reaches down inside the transmission to become disengaged from the shifting rods. When this happens it can become very difficult to get it back in place again, but it is possible to do it by feel. However because the actual problem may lie with in the trans itself, you may never get it back into where it should be, but if it is the trans, no matter what you do now, it won't matter. In the end it sounds like you're going to have to remove the floor to gain access to the inspection cover on the top of the trans. As I mentioned before, the big access cover on the side is accessible for inspection with out having to remove the floor. You can clearly see if the third and fourth gear synchro's are jammed. How comfortable are you working on this transmission, or do you know what you're looking at to recognize a problem ? The other thing is just finding a shop that's capable of working on it. . | ||
| Graham Watson Experienced User Username: graham508 Post Number: 112 Registered: 03-2016 |
Hi Jeff, I am taking the Sgt. Schultz approach right now until I get that inspection cover off and have a look. If that gives no joy then its on to the side cover. Yes I have played with transmissions before and have a pretty good grasp of what I will see (the parts book is a great help). I will not be able to get to it until the weekend but will let you know what I find..... . | ||
| Mike Eames New User Username: mike Post Number: 3 Registered: 01-2005 |
Hi Graham, As you make no reference to having a problem previously, the clue to solving this issue could be that it occurred after a long descent. If it was my problem the first thing I would pay serious attention to is the tie rod at the rear of the gearbox, are the mountings damaged, was the rod correctly adjusted, and are the rubbers in sound condition. I don;t know the weight of an engine and gearbox but this little rod is what prevents the entire assembly from having fun with the radiator, and of course a small movement can effect the gear change mechanism. The next items to inspect are the torque reaction rubbers and the mountings. The mountings are attached to a threaded rod (to enable adjustment) which can and do break. If this happens the assembly may feel firm but could be jammed out of correct alignment. Internal problems with the gearbox is always a possibility, but I would check the above first. Regards, Mike (EPW Registrar) | ||
| StevenDuchscherer Unregistered guest Posted From: 64.31.36.197 |
My 1947 Bentley MKVI (B474CF) got stuck in reverse. Long story short, I thought it was a trans problem, but turned out to be mis-aligned shift gate. It's been a while, but as I recall, I did some manipulating with a screw driver and a clamp to re-align the shifter. (Message approved by david_gore) | ||
| Graham Watson Experienced User Username: graham508 Post Number: 113 Registered: 03-2016 |
Thanks everyone for your help. I will be spending a lot of quality time with B340DA "Jeeves" this weekend and will report back what I have found (fingers crossed). | ||
| Graham Watson Experienced User Username: graham508 Post Number: 114 Registered: 03-2016 |
Update, First rather embarrassing, the gearbox is jammed in second not forth. I have removed the inspection cover on the top of the gearbox and I can see the end of the selector is not in the selector jaw. However I am able to push the 3rd and 4th and reverse selector shafts but the 1st and 2nd selector shaft will not budge. How can I disengage the gear train so that I can get the selector shaft to move? | ||
| Graham Watson Experienced User Username: graham508 Post Number: 115 Registered: 03-2016 |
HA! Victory I played with aligning the selector jaws that I could move and all of a sudden it all works. However I see that the selector shaft "finger" is resting on the left side of the jaws rather than in the middle where I guess it should be. Perhaps when I receive my new mounting rubbers that will correct itself. Thanks again everyone for your help. I owe a large round of adult beverages next time we meet. Cheers | ||
| David Gore Moderator Username: david_gore Post Number: 4290 Registered: 04-2003 |
Christopher Carnley from the UK, our much-valued Early Post-WW2 contributor, has asked me to post the following information on his behalf: For the gearbox question. The gearbox is in neutral state. The upper row is the 3rd motion shaft: Between the 4th and 3rd speed synchro cones is the shiny ring of the 3/4 selector on the sliding piece between the bridge selecting keys. Does that differ from your examination?  My apologies for the delay in posting this image - for some reason, a gremlin intervened to disrupt posting  .  | ||
| Graham Watson Experienced User Username: graham508 Post Number: 116 Registered: 03-2016 |
I guess I should not write emails when tired. What I see that that when the shifte lever is placed in the first and second gear plane the selector "finger" is not sitting in the middle of the jaws but very much to the right side of the jaw as seen when looking down through the inspection cover. I hope that when I replace the rear transmission mount and torque rubbers the alignment improves. Chris, sorry I do not remember but will be sure to look later, thanks for your help. | ||
| ChristopherCarnley Unregistered guest Posted From: 217.42.42.37 |
The misalignment is due to problems with the selector mechanism. The gate and the spherical central connection are more complicated than appears. In the nose of the gate is a 16 ball sliding bearing, but the return is governed internally by a pair of fine gauge opposing springs. These do break making the correct centring of the drop lever impossible. (Message approved by david_gore) |
