Transmission Rebuilding

Jim's comments seem right on the money to me, and he has the driving experience to back it up.

I have personal knowledge regarding two of Pat's questions.

Moonshadow, my Westchester, escaped the interlock retrofit. (The numbers in the Cord Engineering Notes list the cars just before and after mine.) Russ Gerrits, who had the car restored by Don Mates in the early 70s, insisted that everything be as original as possible. So no interlock was installed. Most of the time, during highway cruising, there was no problem. But under load it sometimes shifted back to neutral. This was annoying, but not fatal. Until the day I was climbing the steep Santa Cruz Mountains near my home with an eighteen-wheeler right on my tail and the Cord slipped from third to neutral. Speed dropped instantly, and I could hear the noises of the truck frantically braking and shifting to keep from running over me. Not fun. I had the interlock installed.

I agree with George that the main shift cylinder exerts much more force than needed. (You can shift by hand using the little lever at the front, but try holding back that cylinder by hand!) George built his valve into the side of the elbows on the main shift cylinder. I tried them for a while, and found that with a brief pause you could shift up and down silently every time, cold or hot. Unfortunately my experiment coincided with the terminal decay of the original 70-year-old shift harness in my car, so I could not be certain if occasional missed shifts were related to electric or vacuum. New harness going in now, and I will experiment again. Jury is still out. (It should be noted that with the adjusting valve in place you can still operate normally with the screw in full open position.)

Here's what the Arakelian valve looks like.

Hi Pat,

Trying to do four at once...nothing like being a glutton for punishment. I'll give you my two cents on the transmissions...

1. I don't know of any internal tricks that will help without the interlock. The main reason for the interlock is the high helical angle on the gears results in a large thrust load which causes the transmission to jump out of gear. A good sycronizer fit and good springs for the shift rail detents will help. The other thing that will help is when driving the car don't hop on it especially in second gear.

2. I'd be careful on this one and do a lot more research on the material. An Oilite bushing is a very diferent material from a bronze. I'd be concerned about it's ability to take a high thrust load without deforming. The oilite is designed to be backed up by steel (or whatever) and is very porous so that is holds a fair amount of oil in it's metalic structure. This allows the oil to provide lubrication and the shaft to run on this lubrication. Again the material is designed for a radial load and not a thrust load.

Loctite will not work with the oilite bushing due to the oil in it. I know loctite will not work with bronze but with the steel on the other side it might. You are better off relying on a tight fit between the syncronizer ring and the houseing, then staking it in place. It doesn't take a lot but make sure it is staked in well. Without the staking it in you will blow the syncronizer on the first shift (don't ask how I know).

Regarding the grooves in the rings. I've rebuilt one transmission that did not have the grooves in the rings. This trans was well worn and I don't know the history of it, but the syncronizer cone on the gear was not "clean". There was some bronze deposits on it, it's hard to discribe, but things just didn't look like it was functioning the way it should. Whether this was due to lack of groves or not I don't know.

I'd sum this whole question up this way...for $100 per trans it's cheap insurance to use the proven parts considering how critical these rings are and the cost of having to do it again if something doesn't work right.

3. What George has done is restricted the air flow into and out of the main shift cylinder. It has the effect of "easing it into gear". What happens when you shift is the shfit rail moves the syncronizer towards the gear until the bronze ring in the sync hub comes in contact with the cone on the gear (this requires very little pressure from the shift cylinder). The mating of the two forces the gear to slow down (on an upshift) until the hub and the gear are running at the same speed. At the same time the main shift cylinder builds up vacuum until it has enough force to overcome the spring resistence in the syncronizer so the outter ring slides off the center of the sync and engages the teeth on the gear to lock two together.

Hopefully the time it takes the main shigt cylinder to build up enough vacuum to overcome the release pressure on the sync. is longer then the time it take the sync nd gear to come to the same speed. Otherwise you get a crunching.

What George's modification is doing is increasing the time it takes the vacuum to build up to overcome the release pressure on the sync.

It the transmission is rebuilt right, the sysnc release pressures are set properly and all the linkages and switches set up properly the Cord will shift silently every time. As things become well worn and are not adjusted properly the clunking will start. This is where George's modification comes in handy in prolonging the eventual trans rebuild and avoiding the costly gear replacements.

I'll leave the fourth question for someone else since I'm being called by my daughters for "something important (I don't know what's more important the Cords).

Good luck with the rebuilds and make sure everything is set properly inside the trans before and as it goes back together.

Jim

I have 4-transmissions I am working on right now (easy to do things in quantity) and have some questions.

1.) Has anyone rebuilt and used an early transmission without a clutch interlock. I have an early car and trnsmission and would like to leave it as it was built without an interlock. Are there any internal tricks to internally improve these without the interlock modification.

2.) My machinist suggested purchasing abronze oilite bushing stock (2 7/8" OD x 2 5/8" ID x 5" long (will do about ten syncro's) and use this by inserting the bushing a 1/2" into the syncronizer bore and cutting it off and cutting the 5 degree taper. He suggests LockTite and staking in position. He can also cut the releifs in the ring, but feels it is not necessary. This appears to be much cheaper than buying individual rings and maching. Any thoughts?

3.) At the East spring meet last year, George Arakalien had mentioned that the main shift cylinder is too strong. He has "throttled" down his driver Phaeton with a valve to soften the shifting action. Can anyone comment on this?

4.) I have rebuilt two side shift cylinders with scrap leather for a diaphram. They work fine with positive air pressure. Is there any better material to use, and any suggestions for testing before mating with engine in sub frame.