In Praise of the ZF 8 Speed

[WILDHOBO]

jeez my engine must probably hate me ;-) i think on 25000 miles he saw 5 times up to 4000 rpm ;-)
most of the time im driving it like my old GTD with DSG gearbox

Mine sees 5000 every time it’s on the highway. Every single time. I’m just under 27,000 miles. Those rpm’s are usually on the way up a steep grade in 4th or 5th.

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[WILDHOBO]

jeez my engine must probably hate me ;-) i think on 25000 miles he saw 5 times up to 4000 rpm ;-)
most of the time im driving it like my old GTD with DSG gearbox

I’ve had engines on both ends of the spectrum. Two examples would be a 3.0l v6 that wasn’t ever happy under 5,000rpms. And a 496 big block that red lined at 4,500, and was usually sitting around 2-2500. They’re just different designs. High rpm’s isn’t necessarily bad.

Edit: had some caterpillar diesels that took 17 quarts of oil, and gallons of coolant. Those redlined at 3000. The turbos kicked in at 2000.

 

[Dim]

I’ve had engines on both ends of the spectrum. Two examples would be a 3.0l v6 that wasn’t ever happy under 5,000rpms. And a 496 big block that red lined at 4,500, and was usually sitting around 2-2500. They’re just different designs. High rpm’s isn’t necessarily bad.

wouldnt sau no to a big block on my gladiator ;-) even if i believe that the best engine would probably be the Hemi 5.7. drove a TRX at highht rpm this week end and yeah thats so amazing anf fun

 

[WILDHOBO]

wouldnt sau no to a big block on my gladiator ;-) even if i believe that the best engine would probably be the Hemi 5.7. drove a TRX at highht rpm this week end and yeah thats so amazing anf fun

The 5.7 would have fit the gladiator like a glove. Oh well. Swaps are too expensive, and I’m happy with how mine performs off road. I don’t care if it’s fast on the highway. As long as I can set the cruise at 75, I’m good.

 

[DBravo]

I’ll check when I leave today. At 70 it’s 2000ish or lower from memory

about 1800 at 70mph in 8th gear

 

[WILDHOBO]

about 1800 at 70mph in 8th gear

Sounds about right, unless I’m going up hill.

 

[Hootbro]

One of the best decisions FCA made was incorporating and license build the ZF 8-Speed transmission for it's lineup. It is leaps and bounds better than the Nag1 that was in the JK and also brought new life to the RAM truck Gen 4 models during the mid cycle refresh.

 

[Wheelin98TJ]

about 1800 at 70mph in 8th gear

For what tire size and gear ratio?

 

[Orange01z28]

Just out of curiosity, what are you turning for RPM at 70 mph in 8th?

Or if you have it at a different speed, I can figure it out. I'm curious what the combo of gearing and 37 ends up at.

Thank you.

2100

 

[camodog]

I know I am going to catch hell, but the only reason we went with the 8 speed is because we wanted the factory remote start and…..ACC. With as much long droning highway miles we do I am glad we did and would do it every time.
My first ever auto, and I don’t care, it’s great.

ps- we are also on 37s but still doing the 4.10. Not disappointed

 

[Snocam]

We have the zf in the gladiator and my Ram 2500. Very impressed with both combinations. I realize the aren't identical transmissions, but they both do a great job.

 

[dcmdon]

about 1800 at 70mph in 8th gear

That sounds like you have stock 4.10s.

I'm asking about Orange's RPMs because he has 5.13 gears.

 

[dcmdon]

jeez my engine must probably hate me ;-) i think on 25000 miles he saw 5 times up to 4000 rpm ;-)
most of the time im driving it like my old GTD with DSG gearbox

Saab did an endurance run in the late 80s where they ran a 3 Saab 9000s around Taladega for 30 days non stop. Flat out. Full throttle at max speed, roughly 6000 rpm. Nothing broke.

Subaru did a similar test in 1989 when they introduced the "high performance" Legacy with 140 hp. (It was high performance in comparison to their previous 4 cylinder cars which made about 90 hp). They ran three Legacys for 100,000 kilometers flat out at an average speed over 135 mph. Likely between 6000 and 6500 rpm.

And they did fine.

So in summary. If you worry about running your engine to 5000 rpm every once in a while, you are worrying about nothing.

Unless you run a high mile engine easy fir its entire life and that forms a step on the bore where the rings stop their upward travel. Then you run the engine hard and because of rod stretch, the rings slam into the step cracking a ring.

The solution is not to never rev your engine. The solution is to rev your engine from when its new so the step doesn't form. Or at the least forms farther up the bore.

 

[Wheelin98TJ]

2100

Actual size 37s and no drivetrain loss comes out to 2,185 RPM at 70. Are you sure your speedo is right and it’s 2,100 at 70?

 

[Orange01z28]

Actual size 37s and no drivetrain loss comes out to 2,185 RPM at 70. Are you sure your speedo is right and it’s 2,100 at 70?

Speedo is right according to GPS

2100 is best guess since there’s not a lot of detail on the stock tach

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