Noisy gearbox

[skodajag]

The previous owner of my car (series 2 fhc) had the gearbox rebuilt by a supposedly reputable company. It works fine but is noisy in first and second. I took it to a well regarded E Type specialist who said they’d had the same problem: rebuilt boxes noisy in 1st and 2nd. I seem to recall reading somewhere, perhaps on this forum, that the problem was a faulty batch of bearings, though can’t be sure of that. If and when I have the box out again, does anyone have advice on how to avoid this problem in a future rebuild? With thanks, Jonathan.

[mgcjag]

Just one thread on ...noisy gearbox ..more if you search viewtopic.php?f=2&t=15099&p=123290&hili ... ox#p123290 you need to give more info on what type of noise and when for anyone to try to diagnose...what oil are you useing.....Steve

[skodajag]

Thank you Steve.

[angelw]

Hello Jonathan,
Describe the noise you're experiencing. The only thing that is common for 1st and 2nd Gears is the Synchro Hub they share. The bearings in all cases for the Gears 1st through to 3rd are 3mm (nominal diameter) needle rollers; 4th gear is a direct coupling from the First Motion Shaft to the Main Shaft. Similarly, the bearings for the Lay Shaft Gear Cluster are 3mm (nominal diameter) needle rollers. I say nominal, as where once you could purchase three sizes varying by a small tolerance, now only one diameter is available.

Except for when the Synchro Hub is engaged with a Gear (1st, 2nd, or 3rd), all gears are rotating on the Main Shaft. When a Gear is selected, the Synchro Hub engages with that Gear and the Gear will rotate at the same revs as the Main Shaft, accordingly, its unlikely to be bearings causing the noise, unless its the Needle Roller Bearings of the Lay Shaft. What changes when any of the Gears 1 through 3 is selected, is that there will be load on the Gear Teeth of the selected Gear and the Gear driving it on the Lay Shaft Gear Cluster. There would also be increased load on the Needle Roller Bearings of the Lay Shaft in the vicinity of the selected gear; 1st and 2nd the rear set of Needle Rollers, 3rd the front set.

The noise associated with the Gear Teeth loading and some defect of the Gear Form, or alignment is a Whining. Noise associated with wear of the bearing surface of the Lay Shaft, the corresponding bores of the Lay Shaft Gear Cluster and Needle Rollers is more of a screeching (varying pitch). Accordingly, as the Lay Shaft is a relatively cheap item, the Lay Shaft should be replaced as a matter of course in a Gearbox rebuild. Examine the condition of the surfaces of the tooth form of the Gears on the Main Shaft and the corresponding Gear of the Lay Shaft Cluster.

Regards,

Bill