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MKI / MKII S type 240 340 & Daimler 1955 - 1967

Sync4 gearbox layshaft rumble/rattle ~ clutch out

 
  #1  
Old 11-20-2018, 10:07 AM
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Default Sync4 gearbox layshaft rumble/rattle ~ clutch out

Took the old girl for a spin today (illegally ~ not registered yet). Runs well, very well in fact, temp stable at 70deg C with sliding apron thermostat etc. Tight as a drum, no rattles & very quiet. Dynamat is good stuff.

The gearbox was rebuilt with new bearings, needle rollers, synchro cones etc.

Nothing occurred to cause me alarm but I did make some observations but don't want to ask a question that amounts to how long is a piece of string. If you see my thread you will realise that I've had almost no time behind the wheel of this car if the questions appear strange. I don't know what normal is.

Nevertheless:

1) Is some input shaft/layshaft rumble/rattle normal at idle warmed up with the clutch out in neutral?
2) Do these gearboxes produce a gentle whine as you run through the gears when compared with modern transmissions? Diff is silent.

Regarding layshaft rumble/rattle ~ a chap (5speeds from Florida) on the UK E Type forum states.

" This is a common issue, and the cause is always thought to be bearings. If you have ever worked on these transmissions in any sort of volume, you would know that the main bearings RARELY go bad. People grind reverse often. When you grind reverse enough times you bang up the reverse idler gear and roll the edges over. The reverse idler is always in mesh with the countergear and the banged up portion of those teeth are riding against the countergear in neutral and all other gears... except reverse.

So.... often times a person will have a 4 speed rebuilt with all new bearings and a new layshaft only to still have this rumbling noise.

The cure is simply to deburr the idler gear with a small die grinder."

Any comments on this statement appreciated.
 

Last edited by Glyn M Ruck; 11-21-2018 at 07:58 AM.
  #2  
Old 11-20-2018, 11:52 AM
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Hmmmn , as far as I can remember the idler gear is not in constant mesh with either the mainshaft or countershaft, it is brought into play when reverse is selected it sits on the reverse spindle and the idler gear is moved into position by the reverse lever sliding the idler gear along the spindle (No synchro). The rest of the gears are in constant mesh, so can't see how the guys comments apply to the reverse gear,

Does the rumble go with the clutch depressed ?
 
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Old 11-20-2018, 12:23 PM
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Originally Posted by TilleyJon View Post
Hmmmn , as far as I can remember the idler gear is not in constant mesh with either the mainshaft or countershaft, it is brought into play when reverse is selected it sits on the reverse spindle and the idler gear is moved into position by the reverse lever sliding the idler gear along the spindle (No synchro). The rest of the gears are in constant mesh, so can't see how the guys comments apply to the reverse gear,

Does the rumble go with the clutch depressed ?
Thanks for the response TJ. I have not bothered to check the validity of his claims. Easier to pick other's brains. He seems to suggest that he works on these units frequently which I don't.

Yes ~ the rumble goes completely when the clutch is depressed. It is not as pronounced as typical Italian transmissions or Getrag for that matter. The whine I talk of is not Moss level.
 
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Old 11-20-2018, 12:42 PM
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One trick to stop the ‘mashing into reverse’ is to ‘touch’ the synchro on 2nd before owing into reverse.
T​​​​​his stops the gears spinning, apologies if you already knew about this but a lot of drivers do not.
 
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Old 11-20-2018, 01:09 PM
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If the clutch disengages properly and you wait for the shafts to stop spinning, you won't mash the gears in the first place, touching another gear just stops the shafts spinning quicker. Mashing reverse is just being too hasty.

Remember the days of double clutching prior to synchro boxes, many have no clue how or why they would do it or the need to do it, but if you understand that principle you can still drive a car home with a broken clutch cable, or lost hydraulics.

I taught my kids to do it and my daughter had to use it to get a friends car home and was very happy I had showed her how to drive a manual with no clutch and no gear crunching either ! If you ever owned a car with a plastic toothed automatic clutch adjustment you may well have found a good reason to use it !!!!
 
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Old 11-20-2018, 01:30 PM
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Glyn, difficult to work out if you have a problem, as you have had some pretty good guys work on your car I would not suspect the gearbox immediately, if you had not had the work done, or had someone you were not happy with then I would suspect clutch or gearbox.

I assume you have the JCN box, this is a pretty damn good box and should not whine or rumble, but they do have a characteristic whine in first gear.

I am pretty sure that all the gears are shaved on the later boxes, but on early non synchro boxes they had the prefix SH on the number designating shaved gears, first gear may not be shaved which would probably account for the "normal" whine in first, maybe they kept cost down by not shaving first as it is not used for long so the whine did not matter ? This is opinion, and I may not be fully correct in my comments in this paragraph.

Obvious thing to double check oil levels, I also assume you had a new clutch, it could be coming from the clutch, but difficult to comment without actually hearing it.
 
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Old 11-20-2018, 02:04 PM
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If the 'rumble' stops when the clutch pedal is depressed, you're hearing the input shaft bearing or one of the needle bearing sets. Since you haven't driven the car much, it may be best to put a few more kilometres on her then change the gearbox fluid to see if the noise reduces.

The reverse idler is not engaged with the layshaft until the gear selector fork for reverse is moved.
 
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Old 11-20-2018, 05:26 PM
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Thanks guys. Sorting the wheat from the chaff on forums can be a challenge. Yes ~ New Borg & Beck diaphragm clutch. Stayed with a carbon thrust. Gearbox JBN6956 with Compact Type A DN OD. I'm an **** Virgo & might well be being over sensitive. This car is amazingly quiet. The quieter you make 'em the more obvious NVH issues are. I will arrange to drive an older restoration from the club. My first reaction was not damn something is wrong. Less rumble/rattle than an Alfa 5 Speed in the day & whine more prominent in 1st but not like a Moss. I must also check the setting of the front & rear engine stabalisers. To my knowledge we have the correct rear mounting spring (I have 3). At one time we did have the GB touching the tunnel slightly. I have rear mounting spacer shims but have not used any yet. The mounting is hard up against the floor.

The gearchange is like a hot knife through butter. Slick & smooth & reverse engages without any issues or effort.







I have the longer Hydrostatic slave cylinder but have retained an external return spring. I did not monitor final clutch adjustment. Maybe rechecking adjustment would be a wise precaution as well.

I have been driving Auto Benz cars for years & it's not fair to expect a 1965 car to be as quiet/silent as they are.
 

Last edited by Glyn M Ruck; 11-21-2018 at 07:48 AM.
  #9  
Old 12-12-2018, 11:22 PM
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Have driven a number of cars now. The sync 4 gearbox whines (sings along) on all of them in the intermediate gears & mine is at the quieter end of the spectrum. I'm told that Jaguar changed the gear pitch on S1 XJ6 gearboxes to shut them up so I drove one of them as well. It probably is a little quieter but also whines.

All suffer primary/layshaft rattle to a greater or lesser degree with clutch out at idle.

So for now I'm happy & will worry about other things.

This is probably average whine level. One car I drove was far worse & especially on over-run/trailing throttle (surprisingly).

 

Last edited by Glyn M Ruck; 12-13-2018 at 08:46 AM.
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Old 12-26-2018, 01:48 PM
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Here's my take on Moss and All synchro jag boxes (Ive had a few!) The Moss is obviously noisier in 1st as its a straight cut gear, Now, I find 2nd and 3rd gear in Moss' quieter than All synchro's, All synchro's have a quieter 1st compared to a Moss as its helical, But it still sings, Every all synchro i've had has had a noisier (Volume) 2nd and 3rd to any Moss that i've had (Only slightly mind!) I'm actually going to replace the All synchro box in my MK2 back to a Moss as i love the vintage straight cut whine in 1st and if you use Redline MTF they don't shift too bad either! And being a 1964 it's what it should have! Also a bit of clatter in neutral with the clutch released is perfectly normal IME. You are correct about the later 'K' Series all synchros that were in the very late 60's /70's Jags, Jaguar altered the helical pitch of the gears to quieten them up.
 

Last edited by blot3.8; 12-26-2018 at 02:02 PM. Reason: Typo
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Old 12-26-2018, 01:57 PM
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Compare this MK2 with a Moss! Does'nt 1st gear sound lovely! His valve clearences need checking though!

 

Last edited by blot3.8; 12-26-2018 at 02:04 PM. Reason: Typo
  #12  
Old 12-26-2018, 04:50 PM
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Thanks for the confirmation. Appreciated! You describe well what I am hearing.
 

Last edited by Glyn M Ruck; 12-27-2018 at 06:39 AM.
 
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