twostrokekid Posted June 23, 2020 Report Share Posted June 23, 2020 My TR4A has one of those Fred Flintstone weights bolted on the rear of the gearbox by the drive flange. It was there when I bought the car in 1975 but since then the gearbox has been rebuilt twice, the propshaft has been replaced, the engine has a different crankshaft, a lightened flywheel and the fan and pedestal have been removed and replaced with a thin belt harmonic damper. I just happen to have the gearbox out of the car at the moment and sitting on the garage floor, a job that I really didn’t want to do but the car has been in storage for the last 25 years and the clutch (which has 100 miles on it) was seized solid. I removed the friction plate from the flywheel with a lump hammer and bolster chisel after all the usual tricks failed!! My question is, does anyone actually still drive around with this weight on the gearbox? I know why the factory resorted to this modification but I don’t think all TR’s were fitted with it. Mine is a bit like Paddy’s shovel and bears no relationship to the car that left the Canley factory back in January 1967. I’m tempted to remove it. Should I? Quote Link to post Share on other sites
Geko Posted June 24, 2020 Report Share Posted June 24, 2020 It's an anti rattling damper. Delete. Quote Link to post Share on other sites
Motorsport Mickey Posted June 24, 2020 Report Share Posted June 24, 2020 3 minutes ago, Geko said: It's an anti rattling damper. Delete. Although you may find then that your car/gearbox then has an audible noise from that area, it cost Triumph money in the first place to fit it, companies (especially car companies who are noted for only fitting items they think you really, really need) think they are supplying these items for a reason. I have left mine on for that reason. Mick Richards Quote Link to post Share on other sites
peejay4A Posted June 24, 2020 Report Share Posted June 24, 2020 Called the “lump” if I recall correctly. Quote Link to post Share on other sites
Andy Moltu Posted June 25, 2020 Report Share Posted June 25, 2020 My 4A has one the 6 hasn't (can't recall if it used to or if it never had) I'm sure sure Triumph thought it was a good way of balancing or damping something but I doubt it works like a pendulum in a tower block in an earthquake zone! Quote Link to post Share on other sites
RogerH Posted June 25, 2020 Report Share Posted June 25, 2020 Hi Andy, the 6 cylinder engine does not need the 'lump'. It's a 4 pot thing. Roger Quote Link to post Share on other sites
twostrokekid Posted June 25, 2020 Author Report Share Posted June 25, 2020 I guess the thing to do is leave the lump off and only refit if I get a vibration. It looks a simple retrofit. To be honest I'm as much concerned at minimising the weight when I finally pluck up enough strength to lift the box back in!! Reading through my service history notes I've had the gearbox out 5 times; three times out through the floor and twice with the engine. I was just 23 years old when I first took it out, swapped the clutch and put it back single handed in a day and a half. Now, 45 years later the car is cruelly exposing the frailties of ageing, but I'm damned if I let it get the better of me. ......and just to add insult, the spellcheck auto correct changed lump to limp!! Quote Link to post Share on other sites
stuart Posted June 25, 2020 Report Share Posted June 25, 2020 32 minutes ago, twostrokekid said: I guess the thing to do is leave the lump off and only refit if I get a vibration. It looks a simple retrofit. To be honest I'm as much concerned at minimising the weight when I finally pluck up enough strength to lift the box back in!! Reading through my service history notes I've had the gearbox out 5 times; three times out through the floor and twice with the engine. I was just 23 years old when I first took it out, swapped the clutch and put it back single handed in a day and a half. Now, 45 years later the car is cruelly exposing the frailties of ageing, but I'm damned if I let it get the better of me. ......and just to add insult, the spellcheck auto correct changed lump to limp!! Problem is its really difficult if not impossible to fit to a built car. Stuart. Quote Link to post Share on other sites
Rob Salisbury Posted June 25, 2020 Report Share Posted June 25, 2020 The trouble is gravity increases with age!! ask me how I know this!! Cheers Rob Quote Link to post Share on other sites
ianc Posted June 26, 2020 Report Share Posted June 26, 2020 I removed the lump from 4VC's gearbox when the box chewed its innards back in 1970 and had to come out. I had no idea what the lump was for, so binned it. Have never missed it! Ian Cornish Quote Link to post Share on other sites
mike3md Posted June 26, 2020 Report Share Posted June 26, 2020 You can fit the weight and its steady bracketry after the box is relocated in the car, but before the tunnel is fitted. The clamp around the tail of the box may need bending to open out to fit. On the (too many!) occasions I have had the box out, I haven't been able to remove the clamp part from the weight, so just pulled it (with the weight attached) sideways off the tail with a bit of brute force. Personally I would refit it. As has been said, it might make a difference. Mike Quote Link to post Share on other sites
Andy Moltu Posted June 26, 2020 Report Share Posted June 26, 2020 Let's speculate what that difference it makes might be. Essentially the 4a and 6 gearboxes are the same bar a few holes so it's not for the gearbox. Will a lump hanging off the tail of the gearbox balance much of the vibration related to the engine? Quote Link to post Share on other sites
stuart Posted June 26, 2020 Report Share Posted June 26, 2020 1 hour ago, Andy Moltu said: Will a lump hanging off the tail of the gearbox balance much of the vibration related to the engine? Thats exactly what it was for, Triumph didnt have money to throw around so if they deemed it needed then it was fitted. Unfortunately the 4/4a registrar doesnt post on here otherwise he could probably quote you the relevant factory service bulletin describing it. Stuart. Quote Link to post Share on other sites
Lebro Posted June 26, 2020 Report Share Posted June 26, 2020 So would it be an advantage on a sidescreen car ? bob. Quote Link to post Share on other sites
RobH Posted June 26, 2020 Report Share Posted June 26, 2020 One for sale on e-bay: https://www.ebay.co.uk/itm/Rare-OEM-Stanpart-Transmission-Vibration-Damper-for-Triumph-TR4-and-TR4A-Gearbox/323649823619 Quote: " This service bulletin states that this vibration damper was incorporated on TR4 models at approximately commission number CT 18000. This afore-referenced service bulletin states that fitting this vibration damper will only reduce vibration between engine speeds of 2700 and 3000 RPM. Dealership service centers were instructed to retrofit this crude device to customer's cars if they complained about excessive vibration." I found another reference which states there are different damper weights for O/D and non O/D boxes. Quote Link to post Share on other sites
twostrokekid Posted June 26, 2020 Author Report Share Posted June 26, 2020 It's a classic vibration absorber; a mass attached via a rubber insert. The engineers would measure output flange vibration with an accelerometer and determine the (always) very narrow band of resonance and then attach a calculated spring mass to damp it out. Standard practice in heavy engineering but not so much in today's automotive industry. I managed to remove the lump with the gearbox in situ to lighten the load when lifting out. Now, my genius idea is to turn the mounting prong through 180 degrees so it is pointing upwards and make some sort of temporary handle to help with the fiddly gearbox lift. It's difficult otherwise to hold the rear flange without it turning. Always knew that feature would come in useful one day! Quote Link to post Share on other sites
Bfg Posted June 28, 2021 Report Share Posted June 28, 2021 On 6/26/2020 at 5:17 PM, RobH said: I found another reference which states there are different damper weights for O/D and non O/D boxes. Hey Rob, would you happen to have any more specifics on this ? Thanks, Pete. Quote Link to post Share on other sites
RobH Posted June 28, 2021 Report Share Posted June 28, 2021 Sorry Pete but no details I'm afraid - it is in the 4A parts catalogue. This is a shot of the relevant bit and you can see there are two separate part numbers (circled): Quote Link to post Share on other sites
Bfg Posted June 28, 2021 Report Share Posted June 28, 2021 Thanks Rob, I appreciate your retrieving and posting this info for me. It confirms that this damper weight was deemed desirable enough to override objections from Triumph's bean counters - on both the gearbox and gearbox+overdrive 4-cylinder cars. I was specially wondering if the weight or smoothness of the overdrive unit might negate its function but, of course, the weight is designed as a damper and not a counterweight. The part numbers may reflect a different size, between overdrive and non-overdrive configurations, or else their rubber may be of a different-shore hardness. Perhaps the latter is a mute point after 50+ years of rubber deterioration.. I'll have one fitted in the hope that mechanical vibration is indeed dampened. Cheers, Pete. Quote Link to post Share on other sites
RAHTR4 Posted June 28, 2021 Report Share Posted June 28, 2021 Hi Pete, The Dampers used on the TR4 and TR4A were exactly the same weight. The Damper supplied for the TR4A did have one seemingly odd variation to the TR4 version. The TR4 version was fitted to all TR4A’s with the overdrive gearboxes. Whereas TR4A’s with a non-overdrive gearbox had one different component, the silentbloc bush which is listed as part number 144313. Regards, Richard Quote Link to post Share on other sites
stuart Posted June 28, 2021 Report Share Posted June 28, 2021 2 hours ago, RAHTR4 said: Hi Pete, The Dampers used on the TR4 and TR4A were exactly the same weight. The Damper supplied for the TR4A did have one seemingly odd variation to the TR4 version. The TR4 version was fitted to all TR4A’s with the overdrive gearboxes. Whereas TR4A’s with a non-overdrive gearbox had one different component, the silentbloc bush which is listed as part number 144313. Regards, Richard Do you have any sort of image of that bush Richard? Stuart. Quote Link to post Share on other sites
RAHTR4 Posted June 28, 2021 Report Share Posted June 28, 2021 Hi Stuart, Apologies, my description was possibly not as clear as it should have been. The "silentbloc" bush had a different Shore rating. Regards, Richard Quote Link to post Share on other sites
stuart Posted June 28, 2021 Report Share Posted June 28, 2021 29 minutes ago, RAHTR4 said: Hi Stuart, Apologies, my description was possibly not as clear as it should have been. The "silentbloc" bush had a different Shore rating. Regards, Richard OK thanks Stuart Quote Link to post Share on other sites
Bfg Posted June 28, 2021 Report Share Posted June 28, 2021 Thanks Richard, that's what I was anticipating for a damper aiming to cancel vibration of engine speeds of 2700 and 3000 RPM. This range presumably initiated harmonics between the engine and other parts, whether within the gearbox or perhaps something like the prop shaft (.. evident as an annoying hum ?). As engine speeds drop when the overdrive is engaged so too would the harmonics be altered ..and so the hardness of the damper's bush would need altering if the same damper bob-weight is to correspondingly neutralise those. Cheers Gents, Pete. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted June 28, 2021 Report Share Posted June 28, 2021 (edited) Something says we used 119451 silentbloc bushes to service these lumps. The bush is from the front suspension inner wishbone of Herald/Spitfire Or was it 141481 the lower wishbone bush for IRS car front suspension. No guarantee but perhaps worth a measurement. Spit bush is 3/8” hole TR is 1/2” hole Peter W Edited June 28, 2021 by BlueTR3A-5EKT Quote Link to post Share on other sites
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