Gearbox/Overdrive

[Dave Larnder]

Good day all

 

My 1959 TR3A has a gearbox/overdrive fitted. The gearbox is the type which has the oil filler and level all in one plug on the side.

Recently the car came out of overdrive by itself while at speed, low oil level I hear you all saying, but when I took the side plug out, I got a small stream of oil coming out, so I put the plug back in. The only other explanation I can come up with is ELECTRICS - my bugbear!, however the solenoid is working properly through the 2nd, 3rd and top selection up and down the box and disengages properly when I flick the switch.

My question is: Does the oil level plug STILL give the required level when you have an overdrive fitted? When I filled the box earlier this year for the first time I made sure that I put in the right quantity of oil as per the instructions for a fitted overdrive, and haven't had any problems during the first 2000miles. I must admit that I put in the stated amount, but did not take the level plug out to check if it was overfull even after I had run the car in for the first 1000 miles

Like most ( I won't say all) TR's) I have a small leak coming out of the front of the gearbox but very nominal and I suspect the oil seal in the Extension front cover or the gasket front cover, but as it is such a big job to replace either, I have decided to leave it until it becomes really necessary,

Let's have your thoughts please or your past experience!

 

Dave

[ianc]

Car must be on level ground and have been standing for a goodly time (overnight is ideal) for the oil level to settle.

Yes, the plug on the side is the level for both gearbox and overdrive, but you have to fill slowly as the oil is very viscous (try warming the container in hot water first) and it is very slow to migrate from gearbox to overdrive.

Are you sure that the overdrive's filter (accessible via the big brass nut on the underside) is clear?

Are you sure that the solenoid is pulling the operating lever into the correct position - check with a 3/16" drill on the righthand side (see instructions in Workshop Manual)?

Does the operating lever remain in the operating position with the transmission working (jack the rear wheels off the ground, engage gear and then overdrive, observe the lever)?

Make sure all electrical connections are sound - it only needs one (fuse, overdrive switch, either coil or contact side of relay, isolating switches, solenoid) to be loose for a bump in the road to cause a problem.

Ian Cornish

[Don Elliott]

The wires from my relay go under the floor carpet and when my feet slide back and forth on the carpet (remember LH drive), I have several times accidently disconnected one of the bayonet connectors. If your O/D switch clicks the solenoid and you can hear the plunger going up, then clicking down when you switch out of O/D, then it's not the electrics. It sounds like you have enough oil to me. Like Ian, I suggest you re-check the setting on the RHS of the overdrive with the 3/16" drill inserted. You could also get the back end of your TR up safely on jack-stands, run the engine, click into O/D and have someone else pull down on that small action lever on the RHD before pulling the tunnel. You could help that person by winding a length of wire to it so it would be easier to pull down. Maybe the clamp that the overdrive plunger pulls up on has worked loose and while it pulls up, it is not rotating the shaft that goes through the O/D casing to the RHS.

 

Bill Piggott was loaned a TR2 with O/D on one of his trips to California and the O/D took a long time (like 10 to 20 minutes) for it to "pull in". The owner later reported that the tiny "o-rings" on that cross-shaft were too tight and were preventing the cross-shaft from rotating.

 

I cut a hole on the LHS of my gearbox tunnel and added two other small holes above the screws which secure the solenoid. All these holes are later plugged with rubber plugs. To look at the solenoid, I lift the carpet and remove the large plug. It the same size as for the holes for the floor jack. If I want to remove the solenoid, I remove the two smaller plugs above and remove the slotted screws holding the solenoid with the use of a very very long thin screwdriver. This is shown on my black TR3A. The green TR3A is from a later TR3A where I added a similar plug to fill and check the oil level on a later TR3A which no dipstick on the RHS like the TR2s, TR3s and early TR3As.

Edited December 1, 2009 by Don Elliott

[Dave Larnder]

The wires from my relay go under the floor carpet and when my feet slide back and forth on the carpet (remember LH drive), I have several times accidently disconnected one of the bayonet connectors. If your O/D switch clicks the solenoid and you can hear the plunger going up, then clicking down when you switch out of O/D, then it's not the electrics. It sounds like you have enough oil to me. Like Ian, I suggest you re-check the setting on the RHS of the overdrive with the 3/16" drill inserted. You could also get the back end of your TR up safely on jack-stands, run the engine, click into O/D and have someone else pull down on that small action lever on the RHD before pulling the tunnel. You could help that person by winding a length of wire to it so it would be easier to pull down. Maybe the clamp that the overdrive plunger pulls up on has worked loose and while it pulls up, it is not rotating the shaft that goes through the O/D casing to the RHS.

 

Bill Piggott was loaned a TR2 with O/D on one of his trips to California and the O/D took a long time (like 10 to 20 minutes) for it to "pull in". The owner later reported that the tiny "o-rings" on that cross-shaft were too tight and were preventing the cross-shaft from rotating.

 

I cut a hole on the LHS of my gearbox tunnel and added two other small holes above the screws which secure the solenoid. All these holes are later plugged with rubber plugs. To look at the solenoid, I lift the carpet and remove the large plug. It the same size as for the holes for the floor jack. If I want to remove the solenoid, I remove the two smaller plugs above and remove the slotted screws holding the solenoid with the use of a very very long thin screwdriver. This is shown on my black TR3A. The green TR3A is from a later TR3A where I added a similar plug to fill and check the oil level on a later TR3A which no dipstick on the RHS like the TR2s, TR3s and early TR3As.

 

Hi Don and Ian

 

Thanks for your input, I will check as you say.

Don, I see what you mean about your wires coming undone with your foot, but mine go through the top of the tunnel, so that one is sorted. i also know about the 3/16" drill as I used to do that on my Austin Healey 100/6, so will check. I also see your idea re the solenoid access and will copy, I have a smaller opening in the tunnel to get to the oil filler/level plug, taking the tunnel out is a job and a half thats why I cut the hole for the plug, will use the rubber bungs for the jack point in the floor for the larger hole for the solenoid access. Went out today and everything was O.K. when engaging overdrive in all 3 gears until the car got hot and then it kicked out and back in again quite a few times but most times only momentarily, so I clicked out and drove home in normal gears. Will have to try the filter plug as you say Ian but I dont have the special spanner so I must make one up, silly question I think, but does the oil drain out of the gearbox and overdrive when you remove the filter plug or is there some sort of reservoir arrangement inside to prevent that?

 

dave

[Don Elliott]

Dave - You will need to remove both plugs (the one in the bottom of the gearbox and the big brass one on the bottom of the O/D) whenever you want to drail out ALL the oil. If you only want to clean the filter screen from the bottom of the O/D, only the oil sitting in the O/D will drain out. With only 200 miles on the present oil in your system, you could leave the oil in the gearbox. On the other hand, if you find crud and chips of foreign material in the bottom of the O/D filter, I would change all the oil. When you are finished, you will need to add oil to the fill plug in the side of your gearbox. Then check it after you have driven around the block - then back home again about a mile or so and re-check the oil level again. You will have to add oil at this point to replace the oil that splashed over from the gearbox section into the O/D section.

 

For the large drain plug on my early TR3A O/D, I have a huge hexagon (6-sided) hex and I can use a 1-3/16" across flats socket to unscrew the plug.

 

I also bought two or three very strong magnets that are small enough to fit into the gauze filter "basket" to keep steel chips from circulating. I hope you haven't any chips which might have blocked the oil passages in your O/D.

[Guest colinTR2]

Dave

Years ago I spent some considerable time trying to get my o/d working consistently, even having it serviced at Coventry o/drives. Eventually I removed both baulk switches from the top cover, turned out one of these had a too thick (just) washer under it, sometimes it contacted and sometimes it didn't !!! I seem to remember that it eventually dawned on me that holding the gear lever forward kept it in, and that was the clue.

Very frustrating but in the end extremely rewarding because o/d is great.

cheers

Colin

[ianc]

Dave

Years ago I spent some considerable time trying to get my o/d working consistently, even having it serviced at Coventry o/drives. Eventually I removed both baulk switches from the top cover, turned out one of these had a too thick (just) washer under it, sometimes it contacted and sometimes it didn't !!! I seem to remember that it eventually dawned on me that holding the gear lever forward kept it in, and that was the clue.

Very frustrating but in the end extremely rewarding because o/d is great.

cheers

Colin

 

 

There should be a large magnetic "washer" (509885) with the gauze filter in the overdrive - it's there to trap ferrous particles.

Most of us loosen the large brass plug using a drift of hard wood or soft metal. It is worth drilling a pair of very small holes, diagonally opposite one another, on the outermost edge of the plug. Once the plug has been tightened, a small wire can be threaded through the holes and secured to something fixed, to ensure the plug cannot loosen and fall out.

Ian Cornish

[pfenlon]

Hello Dave after I renovated my TR3A which was next to yours at TR Bits.

 

I had the same problem, and it was a NEW faulty gearbox switch.

 

A new switch means it may or may not work even if shimmed correctly.

 

Love Dons access plugs looks meant to be dont they.

 

By the way Dave the weather here is bloody wicked!