Jumping out of 3rd gear on over-run

tony109 · Jun 16, 2023

A gearbox that jumps out of gear can be a little annoying, and my box has been sliding out of 3rd gear while Over running (engine braking) for a while.. Third Gear remains fully engaged during acceleration, only jumps out when the load comes off..
It's a Series 2a Suffix C Gearbox with lower 1st and rev ratios. This box is coupled to a suffix C transfer box (with the larger dia intermediate Shaft) but with a 2.888: 1, Low transfer box ratio, (Thanks to a new Intermediate gear and suffix A internals)
This gives a really useful low ratio reduction..
However, I now need to resolve the main box jumping out of 3rd gear.. Do you think new main shaft bearings are needed, or something else?

Cheers

steve2286w · Jun 16, 2023

Does this sound similar

Series 3 occasionally jumps out of 3rd gear

Hi I'm a new member here, I'm just in the process of buying a Series 3. It has a few minor problems, one being that it can jump out of 3rd gear when slowing down for junctions. Does anyone have any idea what may be causing this, and how could it be sorted? EDIT - MORE INFO: It's a 1972 SWB...

www.landyzone.co.uk

lynall · Jun 17, 2023

Detent ball or spring.

Anaconda · Jun 17, 2023

My son's did this for all the years he had it, ball and spring did not fix it, worth a try though.

Wildefalcon · Jun 17, 2023

Mainshaft nut loose?

ciderman · Jun 17, 2023

mine jumps out going up hill in third- always has done....

tony109 · Jun 17, 2023

I think the box will need of new set of main shaft and lay shaft bearings. There also appears a bronze bush that carries the 3rd
gear and syncro.. Basically replace all the wearing parts should help a great deal.. In the mean time I will continue to look up the parts..

Gun7354 · Jun 22, 2023

I had this and found it was the gearbox mounting rubbers. Even though they looked ok, once i took them out to replace one was snapped at the bolts and moved the gearbox about 2 inches left and right.

Been perfect ever since

Rich

tony109 · Jun 23, 2023

Interesting you found that to be the cause. My gearbox mountings are sound. If your box could moved the extent you said
was it physically moving the gear selector?
My box isn't jumping out of 3rd gear under load, only dropping out of gear on the over-run.
The 3rd gear wheel, with the Syncro clutch teeth attached appears to run on a Bronze Bush, so any tapper or wear here,
added to any wear in the mainshaft bearings I think are the most likely culprit. I seem to have a bit of gearbox bearing noise on the over Run too. I've ensured it's all topped up with gear oil, but I think The box will needs to come out for new bearings, bushes and seals..

tony109 · Jun 26, 2023

I've invested in a full set of mainshaft and layshaft bearings for the gearbox, along with the Bronze 2nd/3rd gear carrier/ Distance piece, Part no; 571218, together with a all the Thrust washers and seals.
The difference in price between OEM and pattern parts is not surprising.

Gun7354 · Jun 30, 2023

Hi Tony, yes it did move the gearstick by about an inch when the mount was knackerd

Rich

Jumping out of 3rd gear on over-run

tony109

Active Member

steve2286w

Well-Known Member

Series 3 occasionally jumps out of 3rd gear

lynall

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Anaconda

Well-Known Member

Wildefalcon

Well-Known Member

ciderman

Active Member

tony109

Active Member

Gun7354

Well-Known Member

tony109

Active Member

tony109

Active Member

Gun7354

Well-Known Member

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