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MG Midget and Sprite Technical - Gearbox

Just finished a gearbox rebuild on my 70"s midget. The box needed new syncros, 2nd and 3rd gear. The rebuild was straight forward until all was reinstalled and road tested. It will not stay in 3rd gear. I can hold it in, but under acceleration or if the shift lever is not held it will pop out.

I can not fully engage 3rd gear. 1st, 2dn, and 4th, work ok.

All gears engaged ok on the bench test.

Could this be a result of replacing 3rd gear?

I know I have to pull it back out, does anyone have a suggestion on what to look for when I get the side cover back off?
LKS Schwendeman

I cant help...But which box is it?

smoothcase

ribcase

triumph 1500 case

or exotic...ford type 9, datsun, toyota

Prop
Prop

It's a 1970 Midget with a ribcase gearbox.
LKS Schwendeman

A few possibilities. When you put it back together, did you get the "spacers" that go between the front cover and the input shaft bearing and corresponding rear ones installed. They come in different thicknesses to adjust for tolerances and keep the input and main shafts close enough together to keep this from happening.

Another possibility is a worn 3rd/4th slider. Check the internal teeth for wear.

Is the set screw that holds the shifting fork to it's shaft properly tightened?

Is the shift lever completely seated in its housing.

I'm sure others will be along with more suggestions.

Let us know what you find.
Martin Washington

Thanks for the advice guys.
I should add that the gearbox shifted (stayed in each gear) before I took it apart. The rebuild was done because regardless of gear selected it would grind. Downshifting could only be accomplished by double clutching.
When I got the box apart the syncro rings were worn out along with the 2nd and 3rd gear syncro cones.
I got the rebuild kit (bearings, gaskets, lay gear shaft, ect) along with the gears and reassembled.
I did install the shims under the front and rear.
I keep thinking that the main shaft (3rd motion) rear bearing position is suspect.
When I first installed the rear bearing I pressed it all the way to the shoulder. When I installed the main shaft the gears did not line up with the lay shaft. Also the main shaft did not appear to fit all the way into the input shaft (1st motion).
I took the main shaft out and brought the bearing up a bit, reinstalled and the gears seem to line up better.
Does anyone know the correct procedure for installing the rear bearing on the main shaft?
LKS Schwendeman

This thread was discussed between 07/07/2009 and 08/07/2009

MG Midget and Sprite Technical index

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