Overdrive basics - need info

[DaveGT6]

I'm wondering if there as an easy, simple test to check an overdrive unit while my car is apart (body off chassis) and everything is easily reached.
And while I'm on this topic; I've not had a car with electric overdrive before. I checked the owners manual and it has a paragraph or two about it but doesn't provide any real operation information. I'm aware that overdrive can be used only in 3rd & 4th, but engaging & disengaging; In gear? In neutral? Clutch engaged? Clutch disengaged? I'm guessing that the drive train should be in a no-load situation to engage or disengage, but I need educated so I don't waste the OD when I do get the car back together.
TIA

 

[TR3driver]

Not really simple & easy; it needs to be driven at a few hundred rpm to work. But I have done it using my 1/2" drill motor as a power source, and a length of radiator hose (with clamps on both ends) to couple the drill to the input shaft (gearbox on the bench). You'll also need a source of 12v (like a battery charger) to activate the solenoid. Preferably also a pressure gauge and the special fitting, so you can check the hydraulic pressure. https://webspace.webring.com/people/tj/jholekamp/

There is some debate over whether to use the clutch when shifting in/out of OD; but it certainly is not going to damage the unit to be shifted without using the clutch. I generally do use the clutch though, at least for "casual" shifts, as the driveline shock (bang) at part throttle is unpleasant. That doesn't seem to apply at full throttle, but then I rarely shift my J-type ODs at full throttle anyway. (The A-type in the TR is a different story.)

 

[DaveGT6]

Since I don't have any reason to believe it's non-functional I think I'll leave it as is until the car is drivable & I can test it on the road. (Of course, there's no reason to believe it works either!)
I appreciate the operation info also.
Thanks TR3driver.
BTW - Saw a beautiful red (fresh paint) TR3 less than a mile from home this evening. Never saw this car before. Top down... sweet sound... I'm longing for seat time. It's been almost 15 years!

 

[Geo Hahn]

If the drivetrain is in place (and I'm not sure whether it is) couldn't he just raise the rear end off the ground and try it out?

As I recall I did that for an initial test of my OD before hitting the road.

I, too, use the clutch when engaging. On the Type A OD at least there is a real kick in the seat of the pants if that guy is engaged whilst in gear.

 

[hondo402000]

you might a least change the oil in the tranny and OD and I think there is a filter too. and you will get lots of suggestions on what type of oil to put back in the unit too I suggest following the manual

but then my TR6 doesnt have an OD "yet"

Hondo

 

[TR3driver]

I think there is a filter too.

Two of them on a J-type, but if the first one is clean and the magnets look OK, I might not mess with the second one. They are just screens anyway, not very fine.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
and you will get lots of suggestions on what type of oil to put back in the unit too [/QUOTE]
I relatively recently switched to Redline MT-90, which I really like. Not cheap, but worth it IMO.

 

[HerronScott]

I never used the clutch with the A-type overdrive in my TR4A. Never had a problem with it during the 5 years/75,000 miles I used it as a daily driver.

Scott

 

[vagt6]

When in doubt, ask a professional.

Here's what a prominent, professional rebuilder of Laycock ODs say, he recommends <span style="text-decoration: underline">not</span> to use your clutch. Here's the website, full article at bottom of page: https://www.quantumechanics.com/categories.php?op=newindex&catid=11

<span style="font-style: italic">You do not need to use the regular clutch pedal at all. Get to a reasonable speed, say 45 to 50 MPH. Activate the overdrive switch. As the overdrive engages, feather the throttle so that the road speed of the car remains the same and the engine RPM’s are reduced. Shifting out of overdrive is the reverse of this process. Turn the overdrive switch to the off position. As the overdrive disengages back to normal drive, push down on the throttle to keep the car’s road speed the same and increase the engine RPM until the overdrive shift is complete. This again minimizes wear to the overdrive clutch and brake ring. You can now decelerate the car as you would normally. Again, you would not want to shift out of overdrive at too high a speed as you could over-rev the engine and cause damage to it as a result.

We hope this will clear up any questions on the proper way to shift these overdrives to reduce the wear on them and keep them running longer. Thanks! John </span>

 

[RJS]

John at Quantum knows his stuff. When I was looking to have my diff rebuilt a couple of years ago, I was looking in the back of my Classic Motorsports mag. Saw his advert. Stunned to learn his shop was 15 miles from my back door!

All he does is British drive line rebuilds and service. No engine work, no body work, no suspension work. Drive lines and only drive lines. He has a rep worldwide and in the winter his shop is loaded with trans and diff rebuilds for racers all over the world. Also, when I was up in his shop, I saw work orders subcontracted to him from at least two of the big three!.

Bob

 

[Moseso]

While I agree with John that that is the "proper" way to shift the OD -- the way that it was designed for, there is no harm that can possibly occur because of using the clutch. Most simply put, the clutch is neither necessary nor harmful to use.

 

[Marvin Gruber]

My suggestion would be to test is as Geo mentioned. Raise the car up (preferably on a lift, not jack stands)and give it a go. Have done it several times. I don't use the clutch when shifting into O/D but see where it would take the "jolt" out of the shift. To me the "J" type O/D shift is nothing, "A" type lets you know it there.

Marv

 

[TR3driver]

If you read John's words carefully, "do not need" is not the same thing as "recommends not to".