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MG TD TF 1500 - Drop in Engine RPMs When Clutch is Depressed

What are potential causes in a drop of 200-250 rpms from idle speed of approx. 1000 rpm when clutch is depressed? Similar drop in rpms occurs when car is in gear. 1951 TD with completely rebuilt XPAG engine (approx. 500 miles).
ZVL Lambert

Hi,
there is always some drop in revs but large drops are usually caused by clutch overthrow. The clutch stop peg in the pedal box should be adjusted back until the drop is reduced.My car is R/H drive but I presume L/H cars have the same stop.
Ray TF 2884
Ray Lee

I had this once too, when the pilot bearing in the crankshaft became loose.
R.S. Ralph Siebenhaar

Also, check the condition of your engine and trans mounts; sometimes pushing in the clutch is just enugh to shift the engine, and change the linkage angle.

Tom Lange
t lange

You can adjust your clutch rod. The clutch releases to a point and then too much thrust, the throwout bearing can compress the pressure plate extra hard and impose extra load onto the crank thrust bearing surfaces. Good clutch adjustment goes a long way to smooth shifting, too.

I made some custom aluminum pedal spacers for my wife, so clutching & braking is great for her, but driving is a pain for me.

Have fun!
JIM
Jim Northrup

The grim reaper voices his opinion and advises you may have a bent gearbox spigot.

Several incompetent mechanics later,this was the final diagnosis of a friends TD recently.
G Evans

HHUmmm,,,gearbox spigot,,,, I'm assuming that's the input shaft??? Wouldn't that give some sore of vibration?? Lets hope that cause is something else!!!!

SPW
STEVE WINCZE

Regarding adjustment, I have just finished re-fitting my pedal box....('52).
I found that there was no clutch stop fitted to the box, so I made one, on another member's suggestion...
Maybe your pedal box does not have the stop.
This is relatively easy to check, as only four fasteners hold the cover on the box, found under the body, so access is relatively easy.... Just drill a 1/4" hole in the bottom of the box, and add a "post". If you make the mounting hole oblong, you can adjust the location of the post.
Here's a shot of the stop that I just added, and the location. (see image).
Edward




E.B. Wesson

Thanks very much Ray Lee, R.S Siebenhaar, Tom Lange, Jim Northrup, G. Evans, Steve Wincze,and Edward Wesson for your very helpful information. Edward, the photo of the pedal box stop is extremely useful.
Zarrel
ZVL Lambert

This thread was discussed between 18/12/2011 and 19/12/2011

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