• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

TR4/4A How to test Overdrive out of the car

Share this page

S

shoopal

Jedi Trainee
Country flag
Offline
Hi all
I am wondering if it is possible to check the OD without it being hooked up to the motor.
Thanks
 
I use my 1/2" drill motor as a power source. I forget the size offhand, but I've got a short length of straight radiator hose that just fits over the splines on the input shaft, and the nose of the drill chuck; plus a hose clamp for each end. The gearbox sits on the workbench in a crude cradle cut from scrap lumber, while the drill is held loosely in the bench vise. A tie wrap for the speed control on the drill, and a small 12v battery to power the solenoid. (My bench power supply won't deliver the 20 amps or so to activate the solenoid on an A-type).

Not a 100% check, as the drill motor doesn't turn very fast (850 rpm), but good enough to cover most things, including the all important pressure check. I've been keeping my eyes open for a cheap DC motor so I can try running it up to 5000 rpm next time, but haven't found one yet.

There are some more sophisticated setups shown in the articles at
https://www.buckeyetriumphs.org/technical/AOD/AOD4/AOD4.htm
and
https://vintagetriumphregister.org/maintain/TransRebuild/OverDriveA02.pdf
 
Thanks. A lot of information there. I guess that I will drain and replace the 90 wt. and clean or replace the screen
Then I think that I am going to put the motor and Trans into the car and test drive it before I do the tunnel. (that yoke thing is a real pain in the ***.)
If there is some problem, then I can get it back out pretty easily and do the diagnostics as per the instructions.
Thanks for the links.
 
Don't even need the hose...there is a perfect rod machined into the end of the output shaft. The drill will chuck right onto it! The OD runs off the pump, which runs off the output shaft, so it works perfectly. The tranny doesn't really care which end you are turning...it just figures it's a downshift...



Important safety tip...be sure to flip the drill to turn counter clockwise! It will jam the sprag clutch if you spin the other way.
 
Haven't tried it on my OD box, but a motor salvaged from a Maytag washer works well and offers two speeds (and a rinse cycle):

Maytag_zps30d04987.jpg
 
shoopal said:
Thanks. A lot of information there. I guess that I will drain and replace the 90 wt. and clean or replace the screen
Then I think that I am going to put the motor and Trans into the car and test drive it before I do the tunnel. (that yoke thing is a real pain in the ***.)
If there is some problem, then I can get it back out pretty easily and do the diagnostics as per the instructions.
Thanks for the links.
Click to expand...
Your choice, of course. But I would definitely recommend checking the pressure with a gauge before buttoning things up. Low operating pressure can cause subtle problems that become bigger problems later on (like the OD clutch slipping only when hot and climbing a hill) or intermittent shifting problems.
 
shoopal said:
... If there is some problem, then I can get it back out pretty easily...
Click to expand...

Pretty easily? -- you must be younger, stronger, thinner and more agile than me or possibly you just have a higher threshold for pain & strain.

The solo R&R of an OD is doable, but not something I want to do more than absolutely necessary.
 
So let me get this straight. Chuck in a drill on the output shaft. It can stay in neutral? Rev it up. Measure pressure. Put it into gear (which one?) Energize Coil. check for change in input shaft rotation (slow down?) and weird noises. Is that it?
 
So let me get this straight. Chuck in a drill on the output shaft. It can stay in neutral? Rev it up. Measure pressure. Put in gear (which?) Energize Coil. check for change in input shaft rotation (slower) and weird noises. Is that it?
 
Pretty much. 4th gear will do (but any gear would work). I'd also check that the pressure comes back up where it should be when you engage OD.
 
I'm in the minority here, for some reason, but none of the above would spin my rebuilt overdrive on the bench. I had to buy a 2 HP electric cooler motor with a pulley bolted to the rear flange.
 
KVH said:
I'm in the minority here, for some reason, but none of the above would spin my rebuilt overdrive on the bench. I had to buy a 2 HP electric cooler motor with a pulley bolted to the rear flange.
Click to expand...
When I had that problem, it turned out that the clutch linings had swollen, probably from long exposure to solvent. (Long story, but I was substituting the clutch plate from another OD that had accidentally been left in the solvent bucket for a few years.) The OD clutch was dragging when in direct drive.

It should turn easily. The only drag comes from the pump, and it should take practically nothing to turn before the pressure gets built up (and not much even when the pressure is up).
 
Geo Hahn said:
Haven't tried it on my OD box, but a motor salvaged from a Maytag washer works well and offers two speeds (and a rinse cycle):

Maytag_zps30d04987.jpg
Click to expand...

Nice setup. I like the custom shift lever. It's a Craftsman so you know it will last.

Perry
 
Hey Mr. Pumpkin
I couldn't chuck my cordless on to the tailshaft but I can chuck it on to the input shaft. All full of oil, replaced front seal just in case and now I'm ready to spin it up by the input shaft to test the pressure. What direction does it spin? The motor turns CCW looking at it from the rear. so it seems to me that the input shaft should turn CW looking into it from the bell housing.
Is that right or am I going slowly insane
 
That seems right to me.

That's a bearing surface you're grabbing, though. Be sure you don't damage it!
 
TR3driver said:
When I had that problem, it turned out that the clutch linings had swollen, probably from long exposure to solvent. (Long story, but I was substituting the clutch plate from another OD that had accidentally been left in the solvent bucket for a few years.) The OD clutch was dragging when in direct drive.

It should turn easily. The only drag comes from the pump, and it should take practically nothing to turn before the pressure gets built up (and not much even when the pressure is up).
Click to expand...


Here's what I have today, with my transmission and OD out of the car and on the bench. My OD was working great, but whether I've got bearings misaligned or whatever here's something maybe Shoopal can test as well: When grabbing the rear flange and spinning it by hand, does it continue to rotate once you pull your hand away following a spin? Mine stops dead right there. There's no residual spinning from the force of my hand. The foot pounds of pull to rotate the rear shaft is about 3 to 4.
 
With new seals I would expect the flange to not continue spinning.

I also would be reluctant to chuck the input shaft. Better to shift back to the hose idea. Clamp the hose to the shaft, and the other end to a bolt that you can chuck.
 
Hi. I don't have a torque wrench that goes down to 3-4 ft lbs however I did a little test to estimate the torque required to spin the tailshaft.
Let me start by saying that my OD has not been rebuilt but came from a donor car with about 50,000 miles on it. It will not spin after force has been released which I would not expect anyway. There is a lot of friction in there. By the way you did not indicate if the OD was attached to the gearbox when you were testing it. If not, none of what follows means anything.
First I tested it in neutral which should give the lowest readings. I clamped an 18 oz vise grip to the tailshaft knob and the weight of the vise grip was enough to start it turning. Measured 6" from jaw to end. Assuming that the vise grip weight is uniformly distributed then the 18 oz at 3" would result in .28 ft-lbs. In reverse I had to clamp it on the very edge of the flange so the calculation was 18 oz at 1 ft so that the calculation results in .56 ft-lbs. Both measurements far below what you are reporting.

On the other issue of spinning the tranny via the input shaft, I get your all concerns, unfortunately (my wife always complains about my lack of impulse control) I already did it. I examined the input shaft just now and it doesn't have any scars from the operation but I won't do it again (I promise, ha-ha). I still need to borrow trans pressure guages from my friend.

One last question for general discussion. The OD manual that I downloaded (https://www.tonydrews.com/Overdrive/A-type OD manual.pdf) refers to the correct positioning of the valve control lever. That is when the solenoid is actuated, the 3/16" hole on the other side has to line up with the hole on the OD body. Mine does not as the lever goes past the body hole. Should I readjust this?
 
Back
Top