2sp rear question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Nobighurry · 07-31-2019, 03:38 PM

Question - can you shift the rear from H to L without downshifting the trans? The reason. I ask is when hauling I often need to move from H to L but stay in 4th gear - like when climbing hills loaded. Dropping to 3 H would be too low gear. I dont want to tear up the splitter.

C10 - C90 Bill · 07-31-2019, 07:35 PM

Sure can. Just push down on the button, dump the clutch in and out quick, give it some gas and it will shift just fine.

It will actually shift better if you keep your foot on the gas the whole time. Don't hesitate.

Nobighurry · 07-31-2019, 07:55 PM

Awesome. That's what I was hoping for. Just didn't want to tear it up. Thabk you

**Pvmt-Pndr** · 07-31-2019, 08:21 PM

Keep in mind that you need to raise the rpms to get the rear gears to synchronize. I don't have much practice with this yet but the two times I've tried were an epic fail. The rear end was screaming at me until I gave up and popped it back to high. I only did it for my own amusement last time I ran the truck down the road.

I actually found a couple of old YouTube videos that explain how to do exactly what you're asking quite well too. Type in something like how to shift a 2 speed rear end. It's clearly quite an old video and it was 2 parts. They stress not shifting the rear end going down hill ever due to a higher chance of a run away situation.

Airdirect · 08-01-2019, 02:05 AM

When up shifting, raise the 2 speed button, then let up on the accelerator, once you feel the shift take place press the accelerator down. Works real smooth.

When down shifting, lower the 2 speed button, then ease up on the accelerator followed with a quick press of the accelerator down. The easing up allows the gears to go into neutral then you accelerate the drive shaft to allow the gears to re synchronize into the lower gear.

Works very smooth when done properly. Next time I am out in my truck I will try to take a video and demonstrate.

Nobighurry · 08-01-2019, 06:35 AM

Quote:

Originally Posted by Airdirect

When up shifting, raise the 2 speed button, then let up on the accelerator, once you feel the shift take place press the accelerator down. Works real smooth.

When down shifting, lower the 2 speed button, then ease up on the accelerator followed with a quick press of the accelerator down. The easing up allows the gears to go into neutral then you accelerate the drive shaft to allow the gears to re synchronize into the lower gear.

Works very smooth when done properly. Next time I am out in my truck I will try to take a video and demonstrate.

Thank you. That would be great.

C10 - C90 Bill · 08-01-2019, 08:21 AM

Many like to use no clutch, but it will shift smoother and safer with the clutch. As even recommended by the manufacturer.

Airdirect · 08-01-2019, 08:29 AM

Shifting up can be done with the clutch as the drive shaft will slow down when the clutch is disengaged allowing the gears to synchronize. However down shifting will not work with the clutch disengaged as you have no way of accelerating the drive shaft to allow the rear end to synchronize.

David

C10 - C90 Bill · 08-01-2019, 08:42 AM

You just use the clutch like you are shifting a trans gear.

Even though I like all my gears in the trans, I drove 2-Speed Rear trucks for over 18 years.

**Pvmt-Pndr** · 08-01-2019, 01:32 PM

Good videos

"Eaton 2 Speed Axle Part 01" on YouTube
https://youtu.be/SVDSYSBvjgY

"Eaton 2 Speed Axle Part 02" on YouTube
https://youtu.be/osDi3hpovnc

07-31-2019, 03:38 PM	#1
Nobighurry Registered User Join Date: May 2017 Location: Lexington SC Posts: 119	2sp rear question Question - can you shift the rear from H to L without downshifting the trans? The reason. I ask is when hauling I often need to move from H to L but stay in 4th gear - like when climbing hills loaded. Dropping to 3 H would be too low gear. I dont want to tear up the splitter.

07-31-2019, 07:35 PM	#2
C10 - C90 Bill Registered User Join Date: Nov 2001 Location: Moneta, VA USA Posts: 3,064	Re: 2sp rear question Sure can. Just push down on the button, dump the clutch in and out quick, give it some gas and it will shift just fine. It will actually shift better if you keep your foot on the gas the whole time. Don't hesitate. __________________ '60-'72 Chev/GMC Fan GMC 9500 Fan Detroit Diesel Fan Last edited by C10 - C90 Bill; 07-31-2019 at 07:44 PM.

07-31-2019, 07:55 PM	#3
Nobighurry Registered User Join Date: May 2017 Location: Lexington SC Posts: 119	Re: 2sp rear question Awesome. That's what I was hoping for. Just didn't want to tear it up. Thabk you

07-31-2019, 08:21 PM	#4
Pvmt-Pndr Registered User Join Date: Jun 2017 Location: Temperance Michigan Posts: 375	Re: 2sp rear question Keep in mind that you need to raise the rpms to get the rear gears to synchronize. I don't have much practice with this yet but the two times I've tried were an epic fail. The rear end was screaming at me until I gave up and popped it back to high. I only did it for my own amusement last time I ran the truck down the road. I actually found a couple of old YouTube videos that explain how to do exactly what you're asking quite well too. Type in something like how to shift a 2 speed rear end. It's clearly quite an old video and it was 2 parts. They stress not shifting the rear end going down hill ever due to a higher chance of a run away situation.

08-01-2019, 02:05 AM	#5
Airdirect Registered User Join Date: Oct 2016 Location: Powderly Texas Posts: 297	Re: 2sp rear question When up shifting, raise the 2 speed button, then let up on the accelerator, once you feel the shift take place press the accelerator down. Works real smooth. When down shifting, lower the 2 speed button, then ease up on the accelerator followed with a quick press of the accelerator down. The easing up allows the gears to go into neutral then you accelerate the drive shaft to allow the gears to re synchronize into the lower gear. Works very smooth when done properly. Next time I am out in my truck I will try to take a video and demonstrate.

08-01-2019, 08:21 AM	#7
C10 - C90 Bill Registered User Join Date: Nov 2001 Location: Moneta, VA USA Posts: 3,064	Re: 2sp rear question Many like to use no clutch, but it will shift smoother and safer with the clutch. As even recommended by the manufacturer. __________________ '60-'72 Chev/GMC Fan GMC 9500 Fan Detroit Diesel Fan

08-01-2019, 08:29 AM	#8
Airdirect Registered User Join Date: Oct 2016 Location: Powderly Texas Posts: 297	Re: 2sp rear question Shifting up can be done with the clutch as the drive shaft will slow down when the clutch is disengaged allowing the gears to synchronize. However down shifting will not work with the clutch disengaged as you have no way of accelerating the drive shaft to allow the rear end to synchronize. David

08-01-2019, 08:42 AM	#9
C10 - C90 Bill Registered User Join Date: Nov 2001 Location: Moneta, VA USA Posts: 3,064	Re: 2sp rear question You just use the clutch like you are shifting a trans gear. Even though I like all my gears in the trans, I drove 2-Speed Rear trucks for over 18 years. __________________ '60-'72 Chev/GMC Fan GMC 9500 Fan Detroit Diesel Fan

08-01-2019, 01:32 PM	#10
Pvmt-Pndr Registered User Join Date: Jun 2017 Location: Temperance Michigan Posts: 375	Re: 2sp rear question Good videos "Eaton 2 Speed Axle Part 01" on YouTube https://youtu.be/SVDSYSBvjgY "Eaton 2 Speed Axle Part 02" on YouTube https://youtu.be/osDi3hpovnc



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