Join Date: Apr 2001
Location: Central West Virginia
Re: grinding down shift
Normally, I would say it needs a rebuild kit with a new 2nd and 3rd gear. Be a good time to upgrade to a Toploader or a 5-speed. This would be for a transmission that was previously shifting cleanly, but gradually got to the point it would grind the gears.
Since your trans was recently 'rebuilt', this may... or may not be the case. It depends upon the quality of the rebuild. There are four main gears in the trans, 1, 2, 3 and 4. The gears have small teeth on the ends that the synchros slide onto to engage that gear. These snyncro teeth that the sliders engage to are normally sharp and well defined, making it easy for the slider to slide onto. These get rounded off and flattened over time... keeping the gear from engaging properly.
I rebuild a lot of toploaders. Normally, a rebuild consists of a rebuild kit, along with a new 2nd gear, and usually a new 3rd gear as well. You almost always replace 2nd gear, and usually 3rd. If your rebuilder did not replace these gears, it's likely why they are grinding. Downshifts are the first to grind. Upshifts are usually less of an issue.
One thing you could do, is to ensure you are getting proper clutch disengagement. I'm assuming you are using the stock bellcrank linkage. This gives tons of clutch movement... lots more than a hydraulic setup, which is GOOD. However, make sure it is adjusted correctly. The pedal should only have around an inch or so of freeplay at the top of its travel before it starts to disengage. This will give you plenty of disengagement for gear changes.
If the clutch is disengaging properly, the first place I would look is replacing 2nd and 3rd gears in the transmission, as their syncro teeth are likely worn out. If you have photos of them before/during the rebuild, that would be helpful.
For the guy who says his trans works best when cold, changing to 85w140 oil can help. May buy some time before a rebuild is needed. Plus, do not use synthetic in a toploader. May also help the original poster to band-aid things until it can be repaired or replaced.
Last edited by n2omike; 09-04-2019 at 07:33 AM.