View Full Version : TR2/3/3A "Hard" Overdrive Engagement - TR3

04-13-2006, 11:34 AM
When I switch on my overdrive it immediately kicks in, which is a good thing. However, it engages pretty "hard" (the car sort of jolts), somewhat like a "shift kit" feels. When I switch it off, it very smoothly disengages. Is this hard engagment normal?

04-13-2006, 11:41 AM
You can just feather the throttle a bit as you engage the OD- it will feel smoother and should be a little easier on the equipment too. Some even dip the clutch when engaging but I don't feel that is necessary. Likewise you can pick the throttle up a shade as you go back from OD to direct. Pete

04-13-2006, 11:51 AM
Pete is correct in his description of "how to engage overdrive". Too, the A-type unit has a tendency to "slam" a bit more than the J-type unit when engaging.
A good site to reaffirm this information would be quantumechanics.com where John Esposito explains the correct way to engage overdrive. John could be described an a true expert on Triumph overdrives.


04-13-2006, 12:01 PM
Hard engagement is normal, unless it's severe.

Also, be sure to check the oil level frequently. Low oil can cause a wide range of problems in Laycock units.

Enjoy the OD!

04-13-2006, 12:06 PM
I have an A-type in my TR4, it isn't too jarring but I typically am not accelerating when I kick it in. From what I've learned from others, the fluid in the trans can make quite a difference in the performance, so if you don't like what you have, some research on the fluid and a judicious fluid swap may improve things.

04-13-2006, 09:26 PM
I had a 63 volvo P-1800 that had an overdrive, I thought of it as another gear and always clutched when I engaged the OD. Its a lot easier on the OD to clutch and engage the OD. I would much rather replace the clutch than have the OD unit rebuilt, food for thought

04-13-2006, 10:42 PM
Thirty five plus years of overdrive use and rebuilds has convinced me to engage my clutch. Hondo is right it definitely takes a load off the engagement. When you see those grey flakes in the bottom of the brass plug covering the pump screen, they're all from the brake ring and using the clutch will minimize that wear. The thunk or clunk you're getting may be a bit too much clearance between the brake ring and clutch lining.
Tom Lains

04-14-2006, 02:20 AM
Hi Bryan,

TR2/3 and early TR4 use an A-type that's a little stronger shifting than the later TR4/4A/250/early 6.

The reason is a larger accumulator piston. If memory serves, it's 1-3/4" in diameter in the earlier A-type and was reduced to something like 1-3/8" on the later version. This was done... drum roll please... to provide softer engagement! Apparently many Triumph drivers found the rapid and somewhat harsh shift of the earlier A-type a bit disconcerting. The J-type takes it even further and is slower/softer engaging.

Racers really like the earlier version, if they use an overrive. But, one downside is that some of the parts for the earlier version are harder to find.

There are also mods that can be made to all A-type, to make them engage a bit faster. Those mods may not be necessary on the earlier version, but can improve the later one.

Sounds like you've got the early one, which is what would be appropriate to your car.


Don Elliott
04-14-2006, 04:35 PM
In the last 48 years with my TR3A, I have never (well almost never) let up off the gas or depressed the clutch pedal when switching into overdrive. On occasion, I have taken my foot off the gas before I switch and it "clunks" into overdrive. I stronly suggest that this does more mechanical damage to the gearbox and overdrive than a smooth shift. But just after I switch into overdrive, I feather off the gas for a microsecond to ensure that it all engages smoothly.

Just think about it. Triumphs were built for rallies and for racing starting in 1954. Triumph would never have made it a requirement for a rally or race driver to let up off the gas or de-clutch when switching into overdrive.

Don Elliott, Original Owner, 1958 TR3A


04-14-2006, 04:51 PM
Hey, at least it works! I finally broke down after three years of fiddling with my OD and took it to some professionals to get it working. (It has never worked since I got the car three years ago.)

04-14-2006, 04:59 PM
So much for it working! See my latest post "My Overdrive just DIED" /ubbthreads/images/graemlins/cryin.gif

04-14-2006, 06:04 PM
Your clutch pedal has nothing to do with the electrically initiated Laycock overdrive. Using the clutch to operate your overdrive does absolutely nothing but wear out your clutch.

There's lots of good info on the internet about how to operate a Laycock overdrive. Do a Google search, study the stuff on Quantumechanics.com, and save your clutch! /ubbthreads/images/graemlins/hammer.gif /ubbthreads/images/graemlins/lol.gif