Educational Post: OverDrive Testing Jig Part 3 - REAL TEST

Ok I now need some education here.
The jig is working. The motor turns the gearbox at a constant 1725 RPM [according to the plate on the motor, I have no way to verify the speed exactly].

The pressure builds to 400 psi with the solenoid engaged in 4rth gear and the speedometer I have attached is running at about 60kph. With the solenoid disconnected it drops to 40kph so I think it is working ok.

I am seeing the speed fluctuate and hearing some pulsating noises. It could be the electric motor surging or it could be a problem in the OD or gearbox. I did not strip down this box before trying it, I only did a side cover examination.

Please have a look at this video and tell me if you think this is a 'good to go' gear box.

http://www.youtube.com/watch?v=0Rxs6dTvW1g

[I was having some issues with the 3-4 lockout switch not passing enough current to trip the solenoid, so I'll have to go after that problem later].

I'm pretty sure the pressure should only dip slight when switching between OD and non-OD, then return to what it was before. It should not drop to zero. It might have something to do with where you have the pressure gauge hooked up though.

On QuantuMechanics's website when they were talking about different oils they said:

"When spun up on our test bench at 1,000 RPM, it reached a normal pressure of 400 PPSI. When shifting the pressure dropped to 300 PPSI and quickly recovered to 400 PPSI. All was right in the world of overdrives."

And the wobble in the speedo could be the cable. Try lubing it and see if it is better.

pmittler Wrote:

My local auto parts store sells an inexpensive hand held tach for around $60.00. That would give a better idea of input and output RPM.

Rich

Peter I'm with Andrew on the oil pressure, Isn't it the oil pressure that keeps the OD engaged and then helps disengage it. My guess Is there must be an O ring leaking. I haven't looked into how these OD work, as to were the oil flows before and after engagement. Would the solenoid transfer the pressure form one side of the cone to the other during engagement disengagement.

I don't really know how these OD work, But it would be good Information If others here understand the Hydraulics of these unit's.

I found this article in my favorites. At paragraph "LH Type:" it seems to say that when the car is runninng and the power is cut to the solenoid the valve does not close completely and drop the pressure to zero.

http://www.mgb-stuff.org.uk/gearstext.htm

the LH od runs a slight pressure when not engauged, more like 10-20 psi, I doubt that you can get a gauge to read that high and that low and be accurate on either, the od looks like it works fine to me


I would dtill pull the side cover and inspect the syncros and the filter in the OD for the thrust washer before using

Thanks for the responses.

Derek, the speedo was bouncing a little so it could have been 55kph and 45. It was a significant enough change for me to know the shaft was changing speed on engage-disengage.

It took a bit of time for the pressure to build the first time. After running the jig for while it eventually built up to 400. The drop to 'zero' is typical according to the manual I have even though it might NOT drop all the way to zero. Brian is correct that this gauge probably cannot register that low. However on re-engagement after disengagement it returns to 400 within 5 seconds.

I did check and clean the OD mesh - it was spotless and the rubber o-rings were in good condition - pliable and springy to a fingernail push.

I only inspected the baulk rings from the side cover as to properly check them requires a complete tear-down which does not seem necessary given that this gearbox came out of a working car a few years ago [it was a V8 conversion left-over].

Now I will put this one aside and keep it until I have the three conversion projects done - one of which is for a 70 - and I now have a working unit to compare to.