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MG MGA - Transmission locked, 1rst, 2nd, 3rd and reverse
I've checked the archives (A and B) for info but no luck. What would cause a transmission to lock up in 1rst, 2nd, 3rd and reverse, and have direct drive in nuetral? There must be a common cause. 4th appears to be normal.
|G T Foster|
|Somehow you must have 2 gears engaged simultaneously! Loose selector fork?|
|That means it is permanently in 4th, and putting it in anything else locks it. First or third motion shaft bearings loose or failed most often. If it is a 1600 flange output, check the nut on the flange, otherwise trans out.|
|3-4 sliding hub installed backward, perhaps, but then you can't get the front cover and rear housing assembled at the same time.|
More likely the locking bolt for 3-4 shift rod is screwed down tight out of position with the 3-4 fork and sliding hub too far forward. Locking bolts for the forks must be seated in the drilled holes in the shift rods.
Is this a just assembled or a in-use box?
|FRM, and others, |
This is not my car, but a friend's. It is a 73 MGB (very good condition) that had been setting for a long time for an unknown reason. He got it cheap. He says when the flat bed picked it up one rear brake was locked (hmmmnnn) and it had to be "dragged" onto the flat bed. He had the engine and tranny out of the car for engine work. Reinstalled it last weekend. He did put a new seal in the front tranny cover. He seems to think the transmission was OK when removed. I don't know. After reassembly, the car would not roll so I helped him pull it back apart. Also found that the input shaft is a VERY tight fit in the pilot bushing. With pressure plate, clutch and flywheel removed, it goes in fine till about 1/4 to 3/8 inch from the back plate, then becomes tight. Turns out, he forced the transmission into position with C-clamps when he put it together...Ouch! Anyway, the pilot bush looks OK, the input shaft looks OK and the space behind the pilot bush in the crank has been cleand (brake cleaner) and seems OK. We haven't miced anything yet. No idea why it gets tight.
Update..he called last night to say he removed the shift tower, there is a plastic bushing missing from the shift lever. He put the tower back on (sans bushing) and says it now works OK.
Thank for the input. Any and all thoughts are appreciated. Sorry for dragging you in on a B problem, but I feel at home here and the trannys work petty much the same.
|G T Foster|
|Now you tell us. 1968 and later MGB 4-sybchro gearbox is MUCH different than the earlier 3-syncro units. It is about 1/3 larger and heavier, very few of the parts are interchangeable, and the shift interlocks are entirely different. Some of the late model MGB guys may have a better chance of figuring this one out.|
|4 synch are so close to bulletproof that I've only seen one apart, in 1972. It is possible that the 4th synchro ring is stuck on the cone, which means it is in 4th effectively, so everything I said above applies. It is entirely possible that just fiddling with it will or has knocked the ring loose, which would explain it now "working" if that is true.|
The plastic bush is frequently displaced when installing the stick, and causes slop but not trouble, unless it gets jammed in some place blocking some gear(s), but not likely to be the case here.
The "space" behind the pilot bush is of no importance if not full of sand or battery acid. However, the bush is Oilite, and should be soaked in oil, not washed out with Brakleen.
Your pal is not competent to diagnose anything, so get him to report only what actually happens, not what he thinks about it.
Thanks for your inputs and apologies for not properly identifying it as a B. I am aware that the B tranny is much beefer but still functions much the same way as an A.
I am aware that it is an oilite bush and needs to be soaked. I've mentioned this to my friend. This is his first "picnic". We all have to learn...:)
There is no oil in the trans at the moment. Could this be a contributing factor? Most of the trans I've worked on have functioned OK without oil (just as a test).
|G T Foster|
Oil shouldn't matter.
I suggest you pull the side cover and look in. You can see the synch rings and use a small screwdriver to make certain they are free in neutral (I think). Especially check 4th gear (frontmost) one.
If he moved the input shaft forward while doing the seal, it is remotely possible that some rollers dropped out of the 1st/3rd motion shaft spigot and have locked stuff up - obviously not if it works now.
Yes, everyone has to start someplace, no shame there; and, those who have some experience have to try to guess what could possibly go awry, no matter how odd it may seem!
This thread was discussed between 04/08/2012 and 06/08/2012
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