1984 633 5-Speed Won't Go Into First or Second Gear

[BMWtyro]

The title pretty much sums it up: our 633's transmission suddenly stopped going into to first and second "gates". R, 3,4 and 5 work just fine. Nothing else suspicious occurred in the driveline immediately beforehand, and no work was done to the car just prior to this happened.

Y'all's thoughts, please?

Jeff

[635sharknose]

My first guess is that you have so much play on your shifter mechanism that you are not able to push the lever on the gearbox all the way to the left.
Play on the shifter mechanism is a very common issue. Most of the time it is the shifter and all surrounding pins, bushes and levers.

[DesktopDave]

I had that exact problem with my 265, turned out that the gear lubricant was low due water incursion. I had a heck of a time shifting into 1&2 at standstill, even reverse was difficult. New gear lube made a significant difference.

If it's not lube, hopefully it's just a shifter issue. I'm pretty confident that it's not a transmission problem since you can shift into R. I'd guess that 1&2 are difficult because they're synchronized hypoid gears with a very tall ratio and will 'baulk' if the clutch isn't fully disengaging. I believe R is non-synchronized, definitely a spur cut gear.

Those early steel shifter consoles had a habit of loosening up their mounting bolts. Check those two long rear bolts on the mounting "blocks", also verify the rubber internal buffers aren't damaged. Those blocks are part 1 in the RealOEM diagram here. The mounting bolts that loosen up are part 2. Also verify that the locking 'wave' washers haven't split.I prefer to use a chemical threadlocker (like Permatex blue) rather than overtightening the mounting bolts, since I have seen a more than one transmission with snapped-off shifter mount lugs. The rear rubber snub mount can also fail, but you'd definitely feel that in the shifter.

The clutch system has several well-known failure points. Slow leaks from the master cylinder can are contribute to 1/2 baulking, as well as a cracked pedal cluster bracket or loose/dismounted clutch pedal return spring. Slave cylinders can leak into the bell housing, preventing the clutch from disengaging cleanly. That plastic clutch fork pivot pin is another potential problem child.

Those gearboxes do tend to be pretty robust. If this is caused by internal damage, it's easy enough to upgrade the gearbox. The later 260/6 is a bolt in upgrade, but might requires a shifter upgrade or transmission subframe swap. Good time to freshen up the clutch & rear main seal too.

I've seen a few overhaul videos about the 260, seems like a difficult job requiring a good number of specialized tools. It does seem a lot easier than the 265, that's for sure!

[jbd5015]

Im going to agree with sharknose on this one. Over time you may not notice how much play develops in the shift linkage, but now you are seeing the end result! Its all accessible from underneath the vehicle.

There are two types of shift linkage and linkage suspension for these cars. One uses a stamped sheet metal support, and one uses an aluminum "arm" support. The sheet metal design has 4 bolts that attach it to the transmission and get loose overtime. Both designs use bushings that degrade over time.

Are you a DIY owner or do you have a mechanic you use for the old bmws?

[BMWtyro]

Thanks so much, guys! I am (usually) a DIY guy, so I guess that will be how this one will go down.

So: When I consulted my Bentley's E28 service manual, it appears that I will have to drop the driveshaft (hopefully just the front section) to access this shift linkage / steel console situation. Anything else I should know about and/or replace at the same time before I start ordering blocks, bushings, pins, levers and linkages?

Jeff

[635sharknose]

Yes you will have to remove the exhaust and the driveshaft (only front) to fully access the mechanism.
Not sure what is worn on your car, if I were you I would open it up and check before you order parts, they are not cheap.

[BMWtyro]

Thanks, Sharknose, I intend to do that.

Jeff

[DesktopDave]

I'd definitely plan on lubing it all up, but I'd vote for more of a 'whatever you find' errand rather than an 'overhaul the entire center of the car' quest. It is possible to adjust the shifter console with the driveshaft still installed, but oh-so-much easier with all that stuff out of the way. I'll drop the CSB instead of loosening the center adjuster nut. That provides some 'wiggle room' for the driveshaft. It's retained by a thick pin in the transmission output shaft/yoke.

The steel shifter design seems to be far more durable than the later alu design, FWIW. It does use a pair of shifter cups and a coil spring to tension the shifter ball, instead of the later snap-on ball socket.

[BMWtyro]

Thanks for the suggestions, Dave. I honestly thought I had rebuilt that shifter system 5 or 6 years ago, but now I'm thinking that is incorrect.

Jeff

[BMWtyro]

I got under the car today and, without dropping the driveshaft or exhaust, checked the bolts that hold the sheet metal console in. Sure enough, one of the two forward bolts was loose so I tightened it with a small impact wrench (no access from the top side, so not much choice) . . . BUT it still won't go into first or second gear. Also, no noticeable wear on the shift link bushings.

I can move the shifter up and down at least 1/16" by pushing on it from the bottom; could the problem be in parts 8-12 shown in the linked diagram?

https://www.realoem.com/bmw/enUS/sho...diagId=25_0199

[DesktopDave]

I wouldn't think so, although it's not impossible either. That's fairly normal from what I've seen, the rubber snubber at the rear if the assembly always allows it to move up & down a bit. Part #10 here:
https://www.realoem.com/bmw/enUS/sho...diagId=25_0145

I wanted to ask about the slave cylinder & throw-out bearing. If you're sitting in the car, engine off, and you press the clutch pedal in, do you hear a little 'click'? I always hear it on a healthy BMW clutch, always figured it was the clutch spring getting compressed by the throw-out bearing. It's a really subtle sound, definitely not noticeable when the motor is running. If the master cyl isn't pushing enough fluid, the clutch won't fully release.

I'd also consider a quick gear lube level check, see if it's up to the fill hole...it's annoying, but you're down there already...

I'm still leaning toward a clutch problem, still hoping it's not an internal transmission problem.

[BMWtyro]

Thanks, Dave. I'll check the fluid, and no, I hear no click. The depressed clutch pedal feels/sounds exactly as it always has. My "local" (50 miles distant) BMW wrench now thinks that it may be internal problems when we spoke on the phone . . .

Jeff

[carsnplanes]

Does it go in fine when engine not turning/on? or is only hard to engage with engine on?

[BMWtyro]

Nope; engine running or not, the transmission won't go into first or second gear.

Jeff

[carsnplanes]

Nope; engine running or not, the transmission won't go into first or second gear.

Jeff

ohh...now that is interesting! hmmm. Sounding more and more like the transmission, however, did you check the forward bushing? The rod has a forward and aft bushing. The rear of coarse goes to your shift lever lower connection which uses a bushing. The forward one also has a bushing to the coupling which goes to the inner push/pull rod. As long as you're under there, disconnect the rear bushing from your shift lever and try to operate the tranny rod with just the rod in your hand. You should be able to manipulate/twist the rod left and right and push and pull feeling all of the gears. Reverse may be more difficult to overcome the spring load as you twist. Maybe the rod is bent. You'll see when you get under there.
The rod is 10 if you can see it.
shift rod.JPG

[635sharknose]

I would also check the number 9, these can be worn pretty bad.

[BMWtyro]

Thanks, guys. I've been "under there" and nothing feels loose regarding that rod or the bushings on its ends. I even had my wife work the shift mechanism (clutch in) while I looked at it and felt it move; I can see/feel no play in the linkage.

Someone local suggested that a certain nut at the rear of the transmission (where the driveshaft goes) may be loose and affecting the shifter function. Does this sound familiar, and would it be possible to reach if I could drop the driveshaft here in my driveway?

Jeff

[DesktopDave]

There is a nut at the rear of the transmission, it fastens the output yoke to the output shaft. If it had failed, it'd cause a problem with all gears, not just a single pair like 1/2. Those nuts are on there with a lot of torque, I've never actually seen one that's loose (actually, they're a real problem to remove, but that's another issue). There are some other nuts he might have been thinking about, like the one that secures the driveshaft halves, or maybe the steering shaft sleeve under the dashboard?

I'm getting more worried about this being the transmission itself. Seems to me that the gear shifter assembly is OK since you can use it to select all other gears. The transmission is shifting into them properly. It's getting likely that we're talking about an internal gearbox issue. Could be the 1/2 shift fork, 1/2 shift rail, shift selector, 1/2 synchro rings, cone. etc..

This guy makes an overhaul look easy, it's a fun read if you have the time.

[BMWtyro]

Thanks, Dave; you've been PM'd.

Jeff