Datsun FS5W60A 5 speed noise on deceleration

[Arthur]

My 5 speed is rebuilt with the original gears-all in very good condition on inspection both teeth and internal bearing surface, original shafts-all in good condition, needles bearings and races are excellent, all other bearings new, new synchros and seals. Measurements wilthin tolerance with original spacers...

 

Shifts nice, runs nice on acceleration, quiet on acceleration and cruising at speed uphill and under a slight load.

 

However, in a downshift deceleration condition or coasting downhill or under slight throttle downhill it sounds like a can of pebbles! Not a whine. All gears similar noise.

Higher RPM in a given situation the louder it is.

 

Is this typical of these or is something amiss?

 

Thanks

 

 

 

[Stoffregen Motorsports]

Have you checked the joints in the driveshaft? What vehicle is it in. If leaf springs in rear, the pinion could be dipping on deceleration causing a slight drivehsaft misalignment and vibration.

[Arthur]

At the risk of taking some punishment here, the trans is new to my 69 Sprite. I think you are very familiar with the vehicle.
The driveshaft has new Ujoints, apparently orig rubber-bushings/pads at rear. Old but not loose or visually degraded as far as I can see or determine through manipulation. Was actually planning on another little project replacing with new rubber on hand.
 

[Stoffregen Motorsports]

Could the driveshaft be hitting the trans tunnel? Even just the tiniest bit?

 

How did you know I have a Sprite? (two actually, three if you count Dad's new racer)

 

This one pic shows my two Sprites.

[Arthur]

I see you on the MGEXP  Midget/AHExp Sprite site. 

 

Shaft is all new paint and shows no sign of that.

 

Nice, going to the races.

[Stoffregen Motorsports]

I still wouldn't rule out the driveshaft changing angle under decel. If the u-joints aren't within 3 degrees, they may make a fluttering sound.

 

Other than that, have a poke around the rear axle and see if anything is loose. Pinion seal leaking? Pinion flange tight? Lots of back-lash at the R&P?

 

A couple possibilities inside the trans could be a bearing that has lost its cage, or a gear hub that is rubbing up against a gear, like it's lost its detent spring on the gear or the shift rod. Does it click nicely into gear? All gears? Is reverse loose and sloppy?

[Arthur]

Tranny guy got some "ears" so if it still makes noise after this disassembly/reassembly we will hook up the ears and make a determination.

All gears on deceleration make a noise like pebbles in a can.

We see nothing inside the trans in the way of rubbing, grinding...

Per advice we checked the two spacers at the center support member bearing. Advice is the thinner 0.210"spacer with a flat machined in it goes on the front side of the bearing and the thicker 0.235" spacer goes on the back side. We had somehow set them up the opposite on our garage rebuild.

All bearings are checked and double checked and are good.

All springs and balls and plungers in place and good.

Shifts really smooth and easy up and down in all gears. Into reverse easily. Reverse is nice and snug. Snaps in and out the way you like it.

R&P has no noticeable movement up and down, it rotates about 3/8" of lash.

Back off in a gear and you get the noise.

Only put 45 miles on it and find some metal on plug. Stopped driving and disassembled.

[datzenmike]

Could be exhaust pipe rubbing or loose muffler clamp/hanger. Climb under and give every bend in the pipe a good hard shake.

[Arthur]

New exhaust nice and tight

 

[datzenmike]

New is no guarantee. The engine torques to the side under load and the opposite when decelerating. Things move around. Your description of the rebuild more or less says not the transmission so look 'outside the box'

[Arthur]

👍