Unusual new gearbox thingie...

[Island Moose]

I think my truck heard me talking about selling, because she's being fussy....

All of a sudden I noticed a day or two ago that when I downshift from 4th into 3rd, instead of sliding easily into gear as it always has, it feels like I'm grinding gears momentarily before it slips in. I feel whacking of the gear teeth through the shifter. If I double clutch, or wait longer in 4th to bring the revs down, it's OK.

What causes this?

 

[roscoFJ73]

I think my truck heard me talking about selling, because she's being fussy....

All of a sudden I noticed a day or two ago that when I downshift from 4th into 3rd, instead of sliding easily into gear as it always has, it feels like I'm grinding gears momentarily before it slips in. I feel whacking of the gear teeth through the shifter. If I double clutch, or wait longer in 4th to bring the revs down, it's OK.

What causes this?

Sounds like the synchros,try an oil change if it hasnt had one lately.

 

[Greg_B]

I think my truck heard me talking about selling, because she's being fussy....

All of a sudden I noticed a day or two ago that when I downshift from 4th into 3rd, instead of sliding easily into gear as it always has, it feels like I'm grinding gears momentarily before it slips in. I feel whacking of the gear teeth through the shifter. If I double clutch, or wait longer in 4th to bring the revs down, it's OK.

What causes this?

My shifting was getting ratchety in my BJ74, and I thought perhaps syncos. I checked the fluid levels and my t-case was low, and transmission high. Put in a bypass hose till it could be rebuilt and shifting went back to normal.

If your levels are fine and it is the syncros getting funky then look to redline MT90, which is a syth GL-4. http://www.redlineoil.com/products_gearlubricants.asp?subcatID=18

hth's

gb

 

[Island Moose]

Went with a synthetic 90, and Lucas MT additive. It shifts much smoother all around, but downshifting into third is still harder than say 5th into 4th or 3rd into 2nd. I wonder if I should be looking at the plastic cup at the base of the lever?

Also, I checked the freeplay of the clutch pedal (I have vacuum assist as well) and it seems within spec.

Mystified...I realize I'm being picky...it does afterall shift, just not as good as I think it could.

 

[Greg_B]

Went with a synthetic 90, and Lucas MT additive. It shifts much smoother all around, but downshifting into third is still harder than say 5th into 4th or 3rd into 2nd. I wonder if I should be looking at the plastic cup at the base of the lever?

Also, I checked the freeplay of the clutch pedal (I have vacuum assist as well) and it seems within spec.

Mystified...I realize I'm being picky...it does afterall shift, just not as good as I think it could.

I have a 75/90 syth in the BJ60. It can be ratchtey as well, if I try and shift too fast. This tranny was rebuilt, with new syncro's (cept 1st/2nd cluster). Over the past few years I've tried a few different gearoil additives to see the difference, and have ended up with no additive and the synth. Better, but still not good enough: All simply are too slippery. I am going to switch it out to Redline MT-90 as it has the correct "coefficient of friction" to let the synco's do their job.

The plastic cup is a quick easy check...sure, can't hurt at all!

gb

 

[knorrena]

Greg,

Could you provide more details on the bypass kit, i.e., where did you get the fill plug fittings, and do you have part numbers or desciptors of any kind?

Karl