Shifting RPMs advice

[Mikey1989]

As my truck was delivered in Feb 1989, I believe the transmission is the Peugeot BA10/5. But that is an educated guess only. Definitely is the 4L inline 6 with 5-spd manual.

 

The up arrow instrument panel light comes on well before I would normally shift. I assume it is telling me to upshift when it light up?

 

If I am on flat or downhill I'll shift as low as 1500 RPM but on the uphill I like to wait to 2000+ RPMs depending on the hill steepness. 

 

Bottom line I run the RPMs up higher, sometimes much higher, than the up arrow light indicator.

 

I just sold my '77 Chevy Luv 4-speed manual I drove since 1998. And also just sold my '93 Rx7 5-speed i bought new. So, I am driving my new Comanche more like my old Luv, and definitely not how I drove my Rx7 that loved high RPMs ;-)

 

I appreciate any advice from other Comanche drivers with more experience thank my own. I've had this truck since Sept but was not driving it much until recently having finished a bunch of necessary work on it.

[eaglescout526]

17 minutes ago, Mikey1989 said:

The up arrow instrument panel light comes on well before I would normally shift. I assume it is telling me to upshift when it light up?

So this was a gimmick to help with fuel economy. It probably does help with some science but otherwise its a mild suggestion. 

 

As far as shifting at what RPM, shift when ever the hell you want before redline since its a flat tappet cam engine. I shift at certain MPH, like 1st 0-15, 2nd 15-25(or 30), 3rd 25-45, 4th 45-50, 5th 50 for cruising on the streets as thats all I mostly do with no freeway. Freeway after 3rd is based on getting caught up with traffic.

[89 MJ]

Rev it until the valves float, then grab the next gear

 

I have about the same shift points as eaglescout526. If I need to cruise at 40, I’ll grab 5th then, but if I’m accelerating, I rev it out some. That said, you can shift anywhere up to redline. It depends on how the truck is being driven at that time. 
 

For what it’s worth, my truck is a 4.0 on 31s with 4.10s. 

[Ωhm]

There’s a reason why it’s called an idiot light.

[pizzaman09]

8 hours ago, 89 MJ said:

Rev it until the valves float, then grab the next gear

 

I have about the same shift points as eaglescout526. If I need to cruise at 40, I’ll grab 5th then, but if I’m accelerating, I rev it out some. That said, you can shift anywhere up to redline. It depends on how the truck is being driven at that time. 
 

For what it’s worth, my truck is a 4.0 on 31s with 4.10s. 

Actually I frequently take my old Austin Healey up to valve float and then grab the next gear...

 

For the Comanche, typically I shift all over the place, 1500 is a shortshift, 4500 is the end of the world. In the end it's driving a manual, you have the power to choose how and when you shift.  I've driven my Comanche like a big rig hauling a heavy trailer, with slow deliberate shifts, on the flip side I've raced it up to speed as quick as I can banging shifts out.

[89 MJ]

50 minutes ago, pizzaman09 said:

For the Comanche, typically I shift all over the place, 1500 is a shortshift, 4500 is the end of the world. In the end it's driving a manual, you have the power to choose how and when you shift.  I've driven my Comanche like a big rig hauling a heavy trailer, with slow deliberate shifts, on the flip side I've raced it up to speed as quick as I can banging shifts out.

Yup, sounds exactly like how I drive too. Sometimes it’s a race car, sometimes it’s a semi. Most of the time, it’s just a driver 

 

Also, valve float happens somewhere around 6k in an MJ, in case anyone was wondering. 

Edited Saturday at 02:53 AM by 89 MJ
More info

[zomeizter]

17 hours ago, Ωhm said:

There’s a reason why it’s called an idiot light.

[Mikey1989]

I learn so much on this forum. Very cool. I did not know the term "valve float".  OK, so I'll just keep on smooth shifting, ignore the idiot light, and call it good!

[pizzaman09]

2 hours ago, Mikey1989 said:

I learn so much on this forum. Very cool. I did not know the term "valve float".  OK, so I'll just keep on smooth shifting, ignore the idiot light, and call it good!

Valve float is a real thing in like 99% of engine designs.  There is a maximum RPM where the valve spring can not accelerate the valve closed fast enough to follow the cam profile.  This means the valve is floating off of the cam profile.  Depending on if the engine is an interference engine and if the clearance between piston and valve is tight, will determine if you can damage a valve by colliding it with the piston.  That said, it's really hard to get a stock 4.0L spinning fast enough to float the valves, you have to have a complete lack of sympathy for noise and vibration to do that.