Grinding when engaging reverse.

[7T1240]

Had the good fortune to sneak the car out of the garage for a late winter drive this past weekend. At startup, with choke pulled and a low idle, engaging reverse to back out of the driveway was no problem. After a nice long drive and returning to the garage, I overshot my spot a bit. When I selected reverse to back up I got a grinding sound from the tranny. The rpm's were too high, about 1300. Will lowering rpm's relieve the grinding, or is there more to it than that?

Thank,

Gary S.

[Arne]

Gary, that generally indicates that the clutch is not fully engaging with the pedal down. Since it was evident when the car was fully warmed up, I'd check for air in the clutch hydraulics.

The other (more serious) possibility is that the needle bearings between the transmission input shaft and the mainshaft are dragging when they get warm. The would require you to tear down the transmission and replace the bearings. I should think that this problem might make a bit of noise in any gear other than 4th gear - the noise would be worst in first and reverse and get progressively quieter in each gear up from there to 4th. If you have a five speed, fifth would sound similar to third.

[superfunk]

I have experienced this on many older cars (none with spectacular trannys). If it is just when shifting into reverse, I find that it is typically just because your revs are too high (or your car is moving forward too fast, same problem just from the other end). I have not had one of these transmissions apart, but typically (and from what I can tell in the Chiltons manual) there are not syncros on reverse. That is most likely your problem.

[Arne]

If this happens when the revs are high, it is a symptom of something else that isn't quite right - too much drag in the aforementioned needle bearings. If the problem goes away (or is noticeably less) when the idle speed is around 800 RPM, and you don't notice any odd noises as described above, then I'd recommend a gear lube change. Ideally to a synthetic with lots of detergent qualities. I generally use Redline MT-90 in mine.

[zbane]

I am not trying to hijack the thread with this question, just trying to clarify something-

When you drain the old fluid (from the tranny, or the differential) with the intention of using a synthetic (like redline), is it necessary to somehow flush out the old dino based lubricant?

I've been thinking about replacing the liquids in both, but would like to do it correctly, and I imagine that Adam would want to do the change correctly as well.

[7T1240]

If this happens when the revs are high, it is a symptom of something else that isn't quite right - too much drag in the aforementioned needle bearings. If the problem goes away (or is noticeably less) when the idle speed is around 800 RPM, and you don't notice any odd noises as described above, then I'd recommend a gear lube change. Ideally to a synthetic with lots of detergent qualities. I generally use Redline MT-90 in mine.

Hi Arne.

Okay, I'll start by checking to make sure there's no air in the clutch hydraulics. Beyond that, as I mentioned, I don't recall any problem engaging reverse at startup, with the choke on and the revs lower. And I have no grinding on any of the forward gears, either with the car cold or hot. Next opportunity I have to get the car up to full driving temp., I'll reset the idle speed also. As luck would have it, I have two bottles of MT-90 on the shelf, so I'll give this a go as well.

I am not trying to hijack the thread with this question, just trying to clarify something-

When you drain the old fluid (from the tranny, or the differential) with the intention of using a synthetic (like redline), is it necessary to somehow flush out the old dino based lubricant?

I've been thinking about replacing the liquids in both, but would like to do it correctly, and I imagine that Gary (my edit - g.s.) would want to do the change correctly as well.

Am I correct in believing that the synthetic is compatible with the dino-lubricant, so a drain well and refill with synthetic approach is acceptable?

Thanks, Gary S.

[Arne]

Am I correct in believing that the synthetic is compatible with the dino-lubricant, so a drain well and refill with synthetic approach is acceptable?.

Yes. I've always done it that way, and Redline states their products are fully compatible with fossil-oil. No flush is needed.

One thing to bear in mind, though. There are numerous tales of older cars developing leaks after switching to synthetic gear oils - normally at the output seal, or sometimes the shift selector seals. This is apparently because the synthetic cleans built up sludge out, and the old, worn seals can no longer keep the oil in. If you haven't replaced the output seal recently, you may want to consider doing that at the same time. Possibly the speedo-drive o-rings also.

[dta20502]

Hey 7T1240,

"I'll reset the idle speed also"

How do you do that? Can you explain more how to do it?

I got same problem, engine rev too high, 1500 rpm, and won't goes into reverse!! Thanks.

[7T1240]

I finally had some time tonight to address the grinding issue I was experiencing. Some things that I have noticed since the last posts in this thread:

Changed the tranny fluid. Took a long drive last Saturday and, after the car was warmed up, I experienced balkiness shifting into 1, 2 and 3. And reverse required shutting the car off, shifting into reverse, and restarting the car to prevent grinding.

While the high idle speed may have contributed to the grinding problem, it was not the primary cause. I have discovered that when rpm's do not lower to the proper level at idle, if I put my toe under the gas pedal and pull back gently the idle will decrease to 800 rpm's or so. This makes me think I may need to replace the return springs on the carb linkage. Or I may need to replace some bushings on the throttle shaft. Or both.

After doing a search for "grinding" in Engine and Drivetrain and finding this thread -[http://classiczcars.com/forums/showthread.php?t=17539] - I started by checking the adjustment of the slave cylinder. I made some incremental adjustments which either helped marginally to minimize the grinding or made it decidedly worse. (Also made note that the boot for the slave cylinder was dessicated and cracked and that the slave cylinder should probably be replaced.)

Next, back to the manual and looked at the clutch adjustment section. The pedal was higher than the 8" spec. and the free play was excessive. Adjusted these two to reflect the manual settings (10 - 15 mm on the free play). Backed down off the ramps, did some tentative shifts into reverse, and no grinding. Took an extended test drive and shifting was trouble-free. It would seem the problem was - The clutch pedal was out of adjustment!

Gary S.

[DeesZ]

I had the same problem and solution just about a month before I had to replace the slave cylinder due to leakage. (Did the master and hose at the same time as the master and slave often fail within a short time of each other - in my experience, anyway.)