Transmission Noise

[AUSMHLY]

BJ8 transmission gears are quiet when car's on jack stand, loud when driven.

I've taken on the task of rebuilding the BJ8 tranny. The OD works, so I figure if it ain't broke don't fix it.
I've replaced almost all parts, gears, bearings, thrust washers, etc. On the bench, no oil, it shifts smoothly, quiet. In car with 30w non detergent oil, no drive shaft, engine at idle it shifts smoothly and relatively quietly, including neutral and clutch in. On jack stands, drive shaft spinning tires, it shifts smoothly and relatively quietly.

Driving on the road, the tranny shifts smoothly but it sounds a bit whiny in 2nd, 3rd and 4th gears, and when downshifting whiny sound is louder. I've driven the car for 15 years and this is not a sound I've heard before, and other BJ8s are quiet. Drained oil, both magnets show some fine metal, not much though. Oil looks clean, very little debris at all.

1) When car is on jacks, running at idle, no drive shaft, the coupling flange rotates. I can top it with my hand, let go, it spins again. Is that normal?

2 On jacks all gears relatively quiet with idle and 2000 rpm. Loud when driving load is on the gearbox. Is this normal?

3) I have a new clutch and throw out bearing. I noticed the release bearing on the pressure plate is blue colored. I'm not riding the clutch. Would that have anything to do with the not normal transmission sound?

 

[Bob_Spidell]

Did you replace the layshaft? It's a known wear item, and might explain the whine (2nd is always a bit whiny in my experience). Also could be bearings.

Blue on release platen is likely from heat, not a good sign but I have no guess what could cause it except pressure on slave cyl.

 

[AUSMHLY]

Bob, thanks for your interest and help. New layshaft and cage bearings. Rebuilt Laygear. Thrust gap .010
New slave cylinder, hose and new fluid flush.

 

[dezand]

I recently have the same issue after rebuilding the side shift gearbox and overdrive in my BT7. Used a NOS BMC laygear and reverse. Did not remove any gears from the mainshaft as the synchros only have 10k miles on them. Layshaft and all bearings replaced. Laygear endplay set at .007".
Now have low volume whine in all gears except under neutral load (constant speed). Likely issue is mating a new laygear with the old gears on the mainshaft. Switched to 50wt non-detergent and that has helped.

 

[AUSMHLY]

Thanks dezand. Do you think changing the thickness of the front thrustwasher, and rear thurstwasher, moving the position of the laygear would make a difference? Or maybe smaller or larger endplay? I believe the shop manual says .012 endplay.

 

[dezand]

I asked several guys who rebuild these all the time and they said .005 to .012 endplay and to shoot for .005. This information was from Leo Rouf, Healey Surgeons and John Esposito.
When I disassembled my gearbox I measured .035 of laygear endplay. When I bought the BT7 back in 1977 the odometer read 86k miles, so I assume that the gears had that much on them. Back then I replaced the synchros, first gear and a couple of bearings. It always made a lot of noise in first and reverse, especially on decel, but was pretty quiet in the other gears. I attributed it to wear on the laygear first gear, but when I took it apart this year it really didn't look too bad. Just turning the input shaft in first and reverse on the bench made a ratcheting noise and experimenting, I used a large screwdriver to hold the laygear over to one end, basically to eliminate the endplay. Most of the noise went away. So in reality it was the excessive endplay that caused the noise in first and reverse. Now that it is rebuilt, first and reverse are pretty quiet, nothing like it was before.
I think the current gear whine is due to the old laygear being allowed to move back and forth the .035. Under acceleration it moves one direction and under decel it moves the other. So a wear pattern based on that was created on the gears on the mainshaft, and now they mesh with a brand new laygear with no wear, I think this mismatch creates the whine. I think the same thing happens when a rebuilt laygear is installed, the wear patterns don't match anymore. Maybe with continued operation the noise level may be reduced.
I have a BMW coupe with a 5-speed manual and I have noticed it has a very faint whine in every gear except 5th, so maybe it is not uncommon.

 

[AUSMHLY]

I recently have the same issue after rebuilding the side shift gearbox and overdrive in my BT7. Used a NOS BMC laygear and reverse. Did not remove any gears from the mainshaft as the synchros only have 10k miles on them. Layshaft and all bearings replaced. Laygear endplay set at .007".
Now have low volume whine in all gears except under neutral load (constant speed). Likely issue is mating a new laygear with the old gears on the mainshaft. Switched to 50wt non-detergent and that has helped.

Did 50w non-detergent affect the OD? Does it take longer to engage/disengage?

 

[AUSMHLY]

I asked several guys who rebuild these all the time and they said .005 to .012 endplay and to shoot for .005. This information was from Leo Rouf, Healey Surgeons and John Esposito.
When I disassembled my gearbox I measured .035 of laygear endplay. When I bought the BT7 back in 1977 the odometer read 86k miles, so I assume that the gears had that much on them. Back then I replaced the synchros, first gear and a couple of bearings. It always made a lot of noise in first and reverse, especially on decel, but was pretty quiet in the other gears. I attributed it to wear on the laygear first gear, but when I took it apart this year it really didn't look too bad. Just turning the input shaft in first and reverse on the bench made a ratcheting noise and experimenting, I used a large screwdriver to hold the laygear over to one end, basically to eliminate the endplay. Most of the noise went away. So in reality it was the excessive endplay that caused the noise in first and reverse. Now that it is rebuilt, first and reverse are pretty quiet, nothing like it was before.
I think the current gear whine is due to the old laygear being allowed to move back and forth the .035. Under acceleration it moves one direction and under decel it moves the other. So a wear pattern based on that was created on the gears on the mainshaft, and now they mesh with a brand new laygear with no wear, I think this mismatch creates the whine. I think the same thing happens when a rebuilt laygear is installed, the wear patterns don't match anymore. Maybe with continued operation the noise level may be reduced.
I have a BMW coupe with a 5-speed manual and I have noticed it has a very faint whine in every gear except 5th, so maybe it is not uncommon.

I believe you ended up with .007 endplay. Several guys say .005 to .012. Would .004 or .003 endplay help? I believe some of the other British cars specify .003 end play. If we set ours .003 or .004 and it spins freely by hand, what will happen when driven? Do things expand therefore the freeplay reduces and gears could freeze up? Wonder why some other British cars call for .003 and the Healey workshop manual states .012.

 

[dezand]

I remember the guys saying that anything under .005 makes it hard to install the laygear. There isn't a lot of room when the mainshaft is installed to pull up the laygear into position and ensure that the tangs of the steel end washers are in their grooves. There really isn't any thermal expansion differential because except for the bronze thrust washers everything else is steel. For a 200F increase in temperature over ambient the width of the bronze washer would increase by .0002" so I don't see a negative to .003-.004 as long as it spins easily.

 

[AUSMHLY]

There isn't a lot of room when the mainshaft is installed to pull up the laygear into position and ensure that the tangs of the steel end washers are in their grooves.

Especially with hands larger than a child's.
I use grease to hold the front thrust plate to the case and grease to hold the thrust washer to the plate. Reach in with my left hand pull up the laygear then slide the layshaft in 3/4 with my right hand. Apply grease to the rear thrust plate and thrust washer to hold them together. Use a long pair of needle-nose pliers to hold the unit, then slide it into place and push the layshaft through.

 

[AUSMHLY]

Currently using 30w non detergent oil. Hearing a wine when decelerating on 3rd and 2nd. Would draining 1qt of 30w and replace with 1qt 40w help?
Use just 40w?
Use just 50w?
Thought on switching to MT90?
I think a thicker oil may help, but don't want to cause OD issues.

 

[Bob_Spidell]

'Thicker' oil may very slightly lessen the whine, or maybe confirmation bias will do it. I have a somewhat whiny 3.54 diff in my BJ8 and I tried a thicker gear oil--MT90-140 IIRC--and there was possibly a very slight reduction of whinyness (again, confirmation bias?). I'm pretty sure my 0-60 times went from 11.09341s to 11.09342s though.

I went from using various grades of engine oil, up to 20W-50, in my gearbox to MT90 hoping it would quicken engagement; I think it did slightly (again, confirmation bias?). I was surprised that shifting felt noticeably smoother, so likely no confirmation bias there.