Transmission thump

[ybt502r]

I have need of the greater knowledge of the readership - I've an 88" SIII with pretty standard mechanics. I've noticed recently a real reluctance to shift from 1-2 and sometimes from 2-3 when cold. It seems to get smoother/better when warm. As it is now actually nearing spring here in Calgary, I'm glad for that. I think the issue is with 2nd gear - getting into it and sometimes (very occasionally) staying in - it has now and then jumped out of 2nd when I let up the gas (and thus change the stress on the drivetrain).

Accompanying all this is what seems to be a "transmission thump" whereby the whole drive train seems to jump a bit (like when I put in the clutch to go from 2 to 3). I'm hard pressed to say it's shifting any worse, but after the long winter of -20C, I'm not sure I remember last summer. Something's amiss.

I am going to get underneath it and check all the fluid levels - hoping it's something as simple as that - but is there anything (engine mounts?) I need to look at while I'm at it? This is a rebuilt SIII, and I was informed that the transmission was reconditioned at the time (about 7 years ago, and it's not seen a lot of miles since then).

[Jeff Aronson]

Jumping out of gear is often a sign of a weak synchromesh ring. Do you ever double clutch when shifting between gears? If so, do you still have the problem then?

The transmission thump might be any number of things. You should check the u-joints front and rear to see if one or both need replacement. Shake the driveshaft when the car is in neutral [chock the wheels!] - do you get any up and down movement. If you're lucky, greasing the u-joints might take care of that.

Another cause of the "thump" are the bolts that connect the propshaft to the transmission emergency brake and the rear differential. Make sure none of the those bolts are loose.

Also, pull an axle from the case and check the splines. If they are worn [dull teeth at ends] you'll get a twisting and a thunk when you shift gears.

Low gear oil in the transmission and transfer case could cause problems shifting when cold, but they would not cause the "thunking" sounds you're reporting.

Let us know what you find.

Jeff

[CliftonRover]

I agree with all that was said above, but also if second gear is jumping out you should drain your oil and see if any metal falls out of the transmission. Do you do a lot of downshifting from a high speed into second? I had the ring that keeps second from jumping out snap off. This happend in a Tdi powerd 109, with a late series IIA tranny, so there was more potential stress, but when I would let off the throttle it would jump out of gear. can you hold it in gear? I could not, there was too much force.

[ybt502r]

OK, here's the update from an afternoon underneath the Rover. I managed to put away about two quarts of oil into the transmission and transfer case - both were way low. I also put a bit more into each of the differentials, though the overdrive was just fine. I'm not sure if the synthetic oil or the winter was the problem (or both). I sure don't know where the 90W went. I'll drive it over the summer and watch.

I greased the drive shafts and the U joints. Nothing unusual there, though I found the retaining ring on the front drive shaft (that holds a plastic ring that allows the shaft to move in/out) missing. Dirt or whatever can make its way into the splines of the drive shaft. Have to see to that I guess, but I don't think that's the issue as it's the front shaft, not the rear. No play in anything that I could find, though I can turn the rear prop shaft incrementally (between the splines making contact I assume). It's really not much, and I doubt that might lead to anything.

I took it for a drive, and the shifting was much improved (big surprise), though the thumping in 2nd really didn't change. It was easier to get into 2nd, but I could get it to jump out of 2nd by decelerating when in gear. The thumping can be invoked when I put in the clutch when accelerating in 2nd too. I can, however, hold it in gear when decelerating. And as I drove it, the shifting and thumping appeared to get better (as things warmed up), again as before.

So I can drive it pretty much, and the oil greatly improved things, and I can probably live with the 2nd gear issue if I must. Any other suggestions? I don't have a lot of Rover resources here.

One minor question - as I was trying to lube everything, I couldn't figure out (yet again) how to lubricate the rubber bushings on the steering arms. Is this what I need to get a needle for to inject the grease?

[CliftonRover]

some ball joints are sealed meaning you do not need to grease them while others have the normal grease fitting. the 2nd gear issue sounds similar to mine, I would call Les at Rovers North and ask if other gears in the tranny will be affected by this.

[gudjeon]

What I have done with sealed tie rod joints is pull back the boot from the bottom and inject some ep90 into them with a big syringe. Its not grease, but its better than nothing.:thumb-up:

[ybt502r]

I think I can describe the problem a bit better now - as I'm shifting from 1st to 2nd, when I put in the clutch, the transmission gears feel like they move forward (to the front of the truck) in a rather abrupt way - the "thunk". I can feel it especially in the gear shift lever. It's got a bit of a sound with it, but you can feel the movement. There's something again when going from 2nd to 3rd, but it's not a pronounced. There are no issues at all with 3rd or 4th.

I topped up all the fluids last weekend, and that's helped, but it is still hard to get into 2nd (double clutching doesn't seem to make a difference). In reading past posts, I seem to be pointed towards detent springs/balls. I've never had a transmission open, and I don't have the tools to pull the unit from the truck, though I understand I can check these without taking the transmission out?
But does this seem to be the next thing to check, or am I looking a something a bit more involved? Anything to be warned before I "break containment"?

[LaneRover]

My semi-educated guess is that if you have a SIII and it is a SIII transmission that your 2nd gear synchro is going or gone. This would also explain it jumping out of 2nd.

Does it give the same thunk if you shift a bit more slowly? My Rover is a SIIA and many times I shift with out clutching when going from 1st to 2nd. As I let off on the gas I pull it out of 1st then wait a moment to let the engine revs come down a bit and then just slide it into 2nd. Even though there is no synchro on my transmission it goes right in IF it is given a moment to let the engine and transmission rpm's to match up.

If you give your truck a moment to match the engine and transmission rpm's and it goes right into gear then I think that would lean towards it being the synchro.

Brent

[ybt502r]

I finally got to the point of opening up the transmission. I had the "thunk" to deal with along with a broken synchro spring. From all the reading I've done here, I guessed the "thunk" and jumping out of 2nd was due to a loose mainshaft nut. The synchro spring was just broken, of course, but I think perhaps the loose mainshaft might have contributed (?). Anyway, I sourced the special Rover tool to tighten/loosen the castelated nut at the end of the mainshaft, as well as a new nut and locking tab.

So I've spent two days getting to the point to check it - pull the floors, seats, and seat box. Never having done that, it took a while. The PO had put everything together with caulk, so it did not come apart easily. Then I had to clean the whole unit (pretty grimy). As I have an overdrive, I had to drain and pull that too. But lo and behold, the nut was loose (and pretty knackered by the PO obviously using a screwdriver to hammer it tight). So I got the new washer and nut on, tightened it as tight as I could, and put it all back.

The next issue was the synchro spring. Through various other leads here, I found a set of instructions to replace the spring without pulling the transmission. Ha. Good laugh on me. I followed the instructions and removed the transmission top and the selector rods too (that was tricky; hope I got them back in properly). I got where I could see the 3/4 synchro and the springs therein, but there was no way I could manipulate, twist, or force the spring into the one place without one (there are two springs still in place). I gave up - after dropping said spring to the bottom of the transmission and having to maneuver it to the drain plug to get it back. I bolted everything back together.

I've not taken it out for a run, as it got dark here. I need to refill all the units tomorrow, put the floor and seats back, then take it for a drive. I'm going to live with two springs in the synchro I guess.

Unless - and this is the point of this update - can anyone give me any real trick to get that third spring in? Or will I be pretty much fine to keep driving with just two of the three springs in place? I'm hoping that fixing the mainshaft issue will tighten everything up (stop the thunk and dropping out of 2nd gear), and that tighter transmission will keep the stress off the synchro springs. One can hope, I suppose. Any better thoughts?