Manual Transmission Noise

i try and use nuetral and pump clutches

 

GL-5 is too slippery for the synchros. use GL-4 if you don't want these issues.

 

OP any update?

 

So ummm.......have the dealer techs diagnosed it yet?

 

he's probably still using gl-5 and complaining it doesn't shift right

 

Synchronizers don't whine, so discount them. So if it's in the tranny it has to be a bearing. And with this tranny, it has (if I remember correctly) 9 bearings. And considering that you said that the previous owner started off in 2nd gear, he really put a strain on things. But I would start simple. Change the trans fluid. The book says GL-4 or 5, 75-90 gear oil but these trannys prefer GL-4. It's worth the 3 quarts to try this first. And what's with downshifting into 1st at 20-25mph? Try more like 5-10mph. Cheers

 

Welcome to TW!

 

Much Thanks! Retired from 30 years of working on anything that rolled or was towed in. Hope to be able to offer my experience and still pick up a thing or two as I do a little side work to pay my Bar bill. Cheers.

 

The only way I can get my truck into 1st gear when rolling is to force it. I only go into 1st gear when stopped or barely moving. I definitely do not use 1st to slow down.

 

The whine in 1st is normal due to how fast the driveshaft/wheels are overdriving the gears. I just got my truck up to 25 mph and pressed in the clutch and had the same whine. Pulled it out of gear and it immediately went away. Normal.

2021 with Ravenol semi synthetic.

Btw, my Jeep’s AX15 5 speed, my Ranger’s M5OD 5 speed, and my Nissan’s FS6R31A 6 speed all make whining noises in the low gears. It’s inherent to the gears spinning fast like that. You have a lot of moving parts moving quickly, it’s bound to make noise. Sometimes that happens to be a howl/whine.

I will downshift to 1st just fine but not at 25 mph. I don’t however downshift to 1st and just coast with the clutch in. I see no point to that. Leave it in gear and clutch out in whatever gear you’re in going from cruising to coming to a stop, then clutch in and pop trans to neutral right as you stop. Then sit at the stop clutch out chilling in neutral.

 

I would suggest you do not downshift to first at 25mph. Using the stock tire size, which roll 660 revolutions per mile, a diff ratio of 4.30:1, and a 1st gear ratio of 3.98:1, the input shaft is spinning right about 4700RPMs in 1st gear at 25mph. Now....whatever gear you had before that probably had the engine at considerably less RPM. (Let's say we were in 5th...you'd have been at 1000RPMs at 25mph). You're asking the sycro ring to speed up the clutch and input shaft and countershaft 3700RPMS! That's why it's screaming at you. Don't do that. The syncros are designed to deal with small variations in speeds....not 3700rpm variations in speed.

You need to think of the RPMs that everything is spinning. We were out wheeling years ago and a buddy was driving my truck (86 toyota with dual transfer cases and 4.7 gears in one of them, 4:88 gears in the diffs). He was in low low (250:1 final drive) and after clearing a downhill obstacle, let the truck roll about 5mph in 1st gear with the clutch pedal pressed. At 5mph with that final drive the clutch was spinning at 14,000+ RPMS and since it wasn't being squeezed between the pressure plate and flywheel...grenaded. I'm amazed the trans (which was also spinning about that fast) lived.