J type overdrive question.

I have a complete J type overdrive setup for my 1500 Spitfire. It came out at 60k miles because it would jump out of 4th gear. I found a detent ball stusk to the magnetic drain plug. The OD worked fine. The bad is it sat in my dads shop for 20 years.

I have rebuilt these gear boxes before and intend to rebuild this one but am unsure if I should go thru the OD since it sat for 20 years. I pulled the filters and they looked clean and not clogged. I'm thinking just reseal the filter cover, rebuild the gearbox and give it a try.

Any thoughts?

In reply to porksboy:

Really, the only thing on a J type that ever gives trouble is the orings on the two actuating pistons- at least at that type of mileage. Volvo upsized the oring grooves and orings in the pistons a couple of times over the years. There can be bearing troubles, but you should be able to hear them by giving the output shaft a spin after pulling it off the trans.

If you decide to get into it, I'd bet most parts are available through Volvo. They used them into the 90's, although the last few years were a larger unit. I'd bet if you ordered 240 bits, they'd fit fine, and probably be better quality than repro Brit stuff.

One tip- they can be a bit of a bugger to get off the output shaft if you can't engage and run the od unit on the car. With yours sitting in the garage, thats not an option, so you may need to pull the pan off and pry the cone clutch towards the front of the unit to get it to release from the output shaft of the trans. If you do strip it down, you have to line up the splines on the planetary and the overrunning clutch to get it to re-engage the output shaft. If you have the trans apart at the same time, you can use the output shaft as a dummy.

Yeah I had thought about soft bits but when I pulled the filter the oring was soft so I might not futz with them. Build the box, put it in the car and drive without the interior for a few weeks to see if any thing bad happens. I can pull the box out in less than an hour with out the interior.

http://www.quantumechanics.com/

I'm pretty sure he'll be at Carlisle this w/e as well, if you're in the area. John is pretty much the Laycock o/d guru.

For your trans, I'd say just fill it with non-detergent 30 WT and drive it. We installed the same type in our '79 1500. The fun part is the myriad of different ways to swtich the o/d.

I bought a Spitfire parts car for the OD transmission. Pulled it out, changed all the orings, gaskets etc and put in my Mk I. It has worked fine every since. I was using GL4 lube and finally changed to 30 ND oil. The only problem with this transmission is the little pins that hold the shifter in place tend to bind and right now, it won't go into reverse.

Oh yea, John Esposito can actually test the OD to see if its OK before you install it if you care. They aren't the most fun things to remove. I tend to pull it and the motor together.

You definitely need to go through the transmission and fix the detent ball situation. Take a look at everything else at the same time. I've heard the new repro synchros are not too good. I believe they are too thick or something. Look for NOS ones if they need to be replaced.

Chuck up a 1/2" drill to the input shaft of the transmission. Battery charger to the electrical connections. That lets you test the function of the overdrive. I'd expect it to be working and you are most likely good to go. Were it mine, I'd test it this way and then install it.

This would be an awesome thread on our Classic Motorsports board (which needs more traffic).

Per Schroeder wrote: This would be an awesome thread on our Classic Motorsports board (which needs more traffic).

I put it there first. Thought I would see if I got different responses.

I hadnt thought of the drill bit idea. Will it turn fast enough to have enough pressure to engage?

If the od is in good shape hydraulically, it needs around 1500 rpm on the output shaft to generate enough pressure to engage in a car. I think. A 240 volvo will kick in around 30 mph in 4th gear......You can do the math from there. On the floor, maybe a bit less.

Thanks Street, I will give that a try this week end. That should also let me leave the OD engaged for tear down.

porksboy wrote: That should also let me leave the OD engaged for tear down.

Actually, the trick is to engage to od, then keep the solenoid activated as you let the trans spin down to a stop. In the car, you just let it come down to idle, then depress the clutch until the wheels stop, then shut it off. The idea is to let the cone clutch seat gently and not bind up on the splines. Makes a HUGE difference to sliding them off the trans.

porksboy wrote: I hadnt thought of the drill bit idea. Will it turn fast enough to have enough pressure to engage?

Always has for me.

Not surprised the classic board is relatively dead. The software is buggy, it keeps loosing my password and demanding I create yet another one. Thbtt. Much better idea of have the two boards linked or combined. It's not like it's completely different people.

Streetwiseguy wrote:

porksboy wrote: That should also let me leave the OD engaged for tear down.

Actually, the trick is to engage to od, then keep the solenoid activated as you let the trans spin down to a stop. In the car, you just let it come down to idle, then depress the clutch until the wheels stop, then shut it off. The idea is to let the cone clutch seat gently and not bind up on the splines. Makes a HUGE difference to sliding them off the trans.

Forgot to mention- make sure you are turning the trans the correct direction for forward motion when you engage the od. Probably wouldn't hurt anything running on a drill, but engage od in reverse= no more od.