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MG TD TF 1500 - Separating gearbox motion shafts

Collective gurus:

Had a "seizure" while downshifting from 2nd to 1st (thought I was pretty well stopped) to climb a steep hill (at altitude in the CO foothills) and "locked up" the gearbox I believe. Got it forced out of gear into neutral (with help from fellow MGCC members!) Was experiencing a bit of gear grind prior to that in earlier hills going from 3rd to 2nd. Don;t know if that was an early warning sign or rather that I think I was downshifting too quickly and not spending enough time in neutral to get the synchros going at correct speed.

Anyhow symptoms of the gearbox after removal and before teardown were; in/front (1st motion) & out/rear (3rd motion) shafts turn fine when in 4th gear but shafts won't turn at all in 1,2, or 3. All the "upper" gear's teeth look good. My guess is then something with layshaft.

On dissamembly I'm unable to get the 1st &3rd motion shafts apart to get them out of the case. The shafts I suspect are frozen/wedged together at the 3rd/4th syncro. I've tried some wedging of screwdrivers at the arrows in the pix and rapping (medium) on them and also some sideways rapping on the 1st shaft but neither methods free them apart. Don't want to rap too hard so as to break teeth.

I have the Barrie Jones rebuild video but of course his shafts (and everything else) fall apart almost by hand pressures.

1) Am I correct in the shafts should separate at the arrows?
2) Anyone run into this dilemma?
3) Any suggestions for getting the shafts apart?
4) Does it need professional help to get apart? (Any suggestions in the Denver area?)

Thanks all
Randy



R Biallas

Bad indeed. Not your fault, if there was oil in it though. The needle rollers between 1st & 3ed motion shafts have likely disintegrated and jammed the two shafts together. Only thing you can do us drive wedges where your arrows are. Best if the wedges are not hardened, as it is less likely to chip teeth that way. Wear eye protection - the hardened parts can give off evil shrapnel.
Might help if you can apply contrary twisting force to the two shafts.

FRM
FR Millmore

The problem certainly could be the broken roller bearings in the 1st motion shaft. If wedges are driven in where the arrows point in the photo the 3-4 sliding hub should move along its splines on the mainshaft. If it does not move along the shaft an 1/8" or so then the brass 4th gear synchro ring has most likely jammed onto the 1st motion shaft. In this case it should be possible to seperate the main shaft and the 1st motion shaft except that the 1st motion shaft will now have the 3-4 sliding hub jammed on it and will not be able to be removed completely from the gearbox.
Hugh Pite
H.D. Pite

As Hugh says. I assumed that the 3/4 hub just happened to be in that position when photographed, but if it does not move freely then welding of the brass synchro to the 1st motion shaft is possible.
Another member just emailed me about a loose (in the bearing) 1stmoshft, and it got me thinking that under constant heavy load mountain climbing in lower gears, the first mo would be forced backwards by the gear helix. This might cause constant heavy and unlubricated contact on the 4th synchro, getting it very hot. It would also cause a binding load on the shift forks, explaining the difficulty getting it out of gear. I've had similar in other boxes.
Was the 1st motion shaft bearing dead, or the nut loose, or the outer race circlip missing? The trick will still be to force the shafts apart by main force.

FRM
FR Millmore

Thanks all, been out of town trying to forget about it for a while (or think of fresh approaches).
FRM: Think you're probably right in some combination of low oil (wasn't as much as I would I like to have seen upon draining) and the backward tilt from the hills aggravating that area.
Hugh: The "striking dig" works and I can slide it back and forth over both the sliding hub. Have to figure out how to pry it to get the sliding hub to move though.
And couple it with various exploded diagrams from the catalogs and manuals to understand it better.
Both frt/back case bearings seem ok and the front outer bearing circlip/nut etc came off when I pounded the bearing out trying to get the shaft to break free. The inner 1stmot shaft guard is gone due to the banging, but that is easily replaced.
Suspect it is the synchro jammed/fused.
Will see what I can find/get for wedges/pry bar and try that.
Many thanks for comments/ideas.
Looks like I'll be attending the British Conclave here 9/17-18 sans TD!
Randy
R Biallas

Randy, drop me a line off-forum. I may have a document that might be of help to you. Bud
Bud Krueger

Belay that last post, Randy. I just reread your first posting and see that you have Barrie Jones' video. Bud
Bud Krueger

This thread was discussed between 30/08/2011 and 05/09/2011

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