11/64s drill bit tranny mounting trick

[glemon]

My car is running quite well, but the pedal pressure for the clutch is more than I would like, I have been reading up on this and apparently it is a common problem on the 6 cylinder TRs, I have read of two possible solutions, one is to get the right pressure plate (original laycock I believe) the other is using a couple 11/64" drill bits to ensure the transmission is perfectly aligned with the motor so everything lines up better and slides more easily.

Has anyone tried the 11/64th drill bit trick? especially on a car that had a stiff sticky clutch? did it make a noticeable difference?

Thanks, Greg

I tend to intuitively think the pressure plate is the key, but if retightening it down with the drill bits does the trick I would gladly skip spending even more money on the car.

 

[Geo Hahn]

I had not heard that and have to say it makes no sense to me. The clutch plate of course finds it home just fine by sliding on the input shaft and I can't imagine the rest of the bits could cause increased effort.

Have you verified that you have the correct master & slave cylinders?

 

[DNK]

Think it was here but there was a long discussion of the mandatory use of the pegs on the motor when doing the install.
I think Bobby posted most about it.

 

[DrEntropy]

the pedal pressure for the clutch is more than I would like

The mating surfaces of trans bellhousing and engine backplate are kinda "fixed" so it's not likely any drilling of mounts will change that. The relational I.D. sizes of master/slave WILL.

 

[TR3driver]

Just a guess, but it sounds like someone was talking about using the drill bits as alignment pins, in place of the original "dowel" bolts that locate the transmission to the engine. Apparently it is a common problem with the TR6 and Stag that the correct bolts (which served as alignment pins) have gotten lost and replaced with common bolts (where the shank is a bit undersize). (Earlier TRs used actual dowels instead.) That allows the transmission to sag a bit, and not line up perfectly with the crankshaft.

For my Stag, I was unable to find a source of dowel bolts, and so made my own from some 3/8" precision drill rod. Someone else claimed that there should be a "precision shank" aircraft ("AN") bolt, and I found a number, but couldn't find anyone willing to sell at a reasonable price.

I doubt that it will ease your clutch operation any, but it should help reduce chatter and increase the longevity of the gearbox. The Stag came to me with a bad center bearing in the gearbox, which I blame on the missing dowels.

Also, if you are going to tear it down that far, it seems far better to me to put in the correct pressure plate. For one thing, that will reduce stress on the thrust washers, which are a known trouble spot on the TR6 motor. And using the smaller diameter master cylinder can lead to problems with insufficient travel, especially if the pivots are worn.

 

[Minesweeper]

Just to add to what Randall said ... (1) there's no need to use an improvised fix such as drill bits in the TR250/6 as the correct dowels are readily available, and (2) a Buckeye Triumphs article compared different pressure plates and found that the Sachs required substantially less force to operate and was the best choice for a stock horsepower engine.

Scott

 

[DNK]

Which is what I discussed above. Check the archives if your interested Greg

 

[TR3driver]

Here's another discussion, which even mentions used 21/64 (rather than 11/64) drill bits as temporary alignment pins.
https://www.vtr.org/maintain/clutch-laycock.pdf

Personally, I still feel that 3/8" precision dowels (or better yet, precision shank bolts as original) are the best approach. Yes, they do go in very tight (have to tap them into place with a hammer & punch if the holes aren't worn) but that is exactly the idea. 21/64" is .0469" undersize, allowing for as much as .0938" misalignment. Better than nothing at all, but still enough to cause problems IMO.

 

[glemon]

I may have misstated the size (stated from an obviously deteriorating memory)sorry to be away so long, but anywhoo, yes Randall should have been more clear, I will take a look at the archived discussion on this.

Here is the article I found that gave rise to my original question.

https://www.vtr.org/maintain/clutch-laycock.pdf

Randall is probably right, as usual, if I go through the trouble of pulling the parts to access the tranny I might as well replace the pressure plate, need to start saving for that part (more like banking good will with the wife really, after all the money aleady spent, and various misguided representations that "this is the last big thing I need for the car")

Greg

Edit: Just re-read the prior post, yes, that is the article I read, but there seemed to be conflicting opinions on the "drill bit trick" so I thought I would check on forumites actual experience.

 

[HerronScott]

Greg,

Do you know which clutch you put in your car?

Scott

 

[glemon]

The clutch is actually one of the few things I did not replace or rebuild, I did some measurements of the lining and seemed to have plenty of life left in it, and all looked good, so left alone, I did some limited reading on the pressure plate issue before I put things back together, and thought I might be in better shape with the old item (car ws off the road for many many years, but don't know exactly how long) than new. Not sure the Brand, but as I recall it looks more like the Laycock than the Borg and Beck described in the articles I have seen.