steve lloyd Posted May 27, 2022 Report Share Posted May 27, 2022 Can someone assist please. I have a 1965 TR4 with a gearbox that is synchronised going up gear but not synchronised coming down. It has an overdrive attached with O/D operable in 2nd, 3rd and 4th. Q - Is this a TR4 gearbox Q - If not and I were to replace it with a TR4 gearbox would the same O/D unit fit Many Thanks STEVE Quote Link to post Share on other sites
Lebro Posted May 27, 2022 Report Share Posted May 27, 2022 Hi Steve. It's not possible for synchro to work going up, but not going down, what is happening is the synchro is worn, & not working very well, going up through the gears is much less demanding of the synchromesh, as when the clutch is down the input shaft (& laygear) slow down naturaly towards the speed required to mesh nicely in the next higher gear. When you change down the opposite is true, the input shaft needs to speed up. It does sound as if your box is a TR box as the saloon boxes did not have overdrive on 2nd gear. I would look into having your gearbox overhauled rather than buying another (unknown ) box. Bob Quote Link to post Share on other sites
RogerH Posted May 27, 2022 Report Share Posted May 27, 2022 (edited) Hi Steve, Welcome to the forum if you can see the clutch actuator lever on the left side of the GB then you should be able to see the GB serial number. A TR4 would be CT xxxxx like this GB Number Roger Edited May 27, 2022 by RogerH Quote Link to post Share on other sites
BlueTR3A-5EKT Posted May 27, 2022 Report Share Posted May 27, 2022 Does the gear box go ‘crunch’ when you engage reverse, when stationary? Maybe clutch adjustment if it is the adjustable type. Quote Link to post Share on other sites
monty Posted May 28, 2022 Report Share Posted May 28, 2022 15 hours ago, BlueTR3A-5EKT said: Does the gear box go ‘crunch’ when you engage reverse, when stationary? Maybe clutch adjustment if it is the adjustable type. Mine does that sometimes. Nice smooth changes in all other gears but reverse can sometimes take a couple of attempts. Usually quire smooth but occasionally a ‘crunch’! Car is a 4A. Did not think there was any clutch adjustment? Quote Link to post Share on other sites
ianc Posted May 28, 2022 Report Share Posted May 28, 2022 When going down the gears, good idea to heel-and-toe in order to speed up the input shaft, thereby reducing the load on the synchromesh. Alternatively, engage the lower gear more slowly - don't ram it through! The TR4, with original style clutch, has adjustment at the push rod on the slave cylinder. And, in fact, many of us using diaphragm clutches, retain the adjuster and its return spring. Ian Cornish Quote Link to post Share on other sites
TR4ffic Posted June 6, 2022 Report Share Posted June 6, 2022 On 5/28/2022 at 10:10 AM, ianc said: When going down the gears, good idea to heel-and-toe in order to speed up the input shaft... ...or double de-clutch Quote Link to post Share on other sites
ianc Posted June 6, 2022 Report Share Posted June 6, 2022 Double de-clutching is fine unless you are decelerating, with your right foot operating the brake - in this case you need the heel of the right foot to push the accelerator. This is heel-and toe. Ian Cornish Quote Link to post Share on other sites
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