Cruising RPMs

[362cuinxh]

Hi everyone, nooby here. Planning on an LS swap and I want to cover all the bases since this is not going in performance car. I am curious what the stock car cruising rpms are at 65 mph. I know it is fairly low. One reason for the LS swap is I am after not only performance but milage too. Worked out OK when I went with a 4.3L V6 at the time over a 350, but now that engine is completely worn out. I do have a 4L60E in it now and to my knowledge a LS1 will bolt to it and then get the right ECM. This is a ground up project and I want to get the right gearing.

[Thedub]

Hi everyone, nooby here. Planning on an LS swap and I want to cover all the bases since this is not going in performance car. I am curious what the stock car cruising rpms are at 65 mph. I know it is fairly low. One reason for the LS swap is I am after not only performance but milage too. Worked out OK when I went with a 4.3L V6 at the time over a 350, but now that engine is completely worn out. I do have a 4L60E in it now and to my knowledge a LS1 will bolt to it and then get the right ECM. This is a ground up project and I want to get the right gearing.

My 02 ws6 cruises at about 2000 at 65. Maybe a little less. I don't drive 65 that often....ls1 with the same trans and a 2500 stall.



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[362cuinxh]

I guess that brings up another question: What is the stall speed on a torque converter behind a LS1? My current stall speed is around 1800 rpms

[Thedub]

I guess that brings up another question: What is the stall speed on a torque converter behind a LS1? My current stall speed is around 1800 rpms

I think it's 15 -1800.


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[362cuinxh]

Well, might be able to use my current lock up converter then. I kind of wish it had a lower stall speed though

[Thedub]

Well, might be able to use my current lock up converter then. I kind of wish it had a lower stall speed though

I would Google it, I'm not a 100 percent sure.


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[362cuinxh]

I did giggle it, and I get a range of answers. But most are in the 1800 rpm range. But it doesn't hurt to check on that. The answers all came off forums, so there is a chance of error. Just checking if anyone knows for sure

[oldmanZ28]

98-02 LS1 OEM convertors are 1800 stall rated and have lock-up capabilities. If GM thought a lower stall RPM rating would be better,they would have gone that route AND I agree.
Automatics came with 2.73s' or 3.23s' rear end gearing,mine is 3.23. Torque convertor lock-up occurs(when the computer allows it),typically,at 35-40 mph. When I'm 'cruising' at that speed and the convertor locks,rpm drops to about 1200 and the engine starts 'lugging',not a good situation for the engine.
When I had a TCI 2800 and with my current Yank SS3600,lock-up at the mph didn't change as lock-up and stall rating are two different and independent things.
When I was running the TCI 2800 and Yank SS3600 with 4.56 rear end gears,still lock-up mph was not affected/changed. But with the 4.56s','lugging' was diminished as the drivetrain had a better mechanical advantage over the resistance/weight of the vehicle.
MPG with 3.23s' for many trips from Ohio to Florida was consistently 24.5 at legal freeway speeds,mpg with 4.56s' for 4 trips from Ohio to Florida was consistently 21.5 at freeway legal speeds. On one trip with the 4.56s' returning to Ohio on I26 across South Carolina,I hooked up with a fast moving group of cars and was in cruise control at 4000rpm for about an hour.

[Whamhammer]

Hi everyone, nooby here. Planning on an LS swap and I want to cover all the bases since this is not going in performance car. I am curious what the stock car cruising rpms are at 65 mph. I know it is fairly low. One reason for the LS swap is I am after not only performance but milage too. Worked out OK when I went with a 4.3L V6 at the time over a 350, but now that engine is completely worn out. I do have a 4L60E in it now and to my knowledge a LS1 will bolt to it and then get the right ECM. This is a ground up project and I want to get the right gearing.

What car is this for? Your info says that you have an '05 Camaro?

What the guys are telling you would only be correct for your car if you had the same axle ratio and just shy of a 26" tire, if either of those are different it will be higher or lower, dependent on the percentage of overall change.

[362cuinxh]

OK, small confession. I don't have a Camaro. I had a helluva time registering on here, so I put Camaro in the spot. What I have is an 86 Jeep Cherokee that has had a Chevy transplant and due for an update again. This time around will leave only the body as an original Jeep part. That being said, the Jeep will see lots of long distance driving as well as daily driving use. I don't need low diff gears since I have unbelievable crawling gears already. What I am looking for is good milage on those long distance trips. I have a 31 gal tank for that already and I want to be able to afford to fill it. I talked to a guy from the local hot rod shop and he told me to expect 20 - 22 mpg That would be nice. That is what I started with when it had a 2.8L V6. More than that would be even better

[SMWS6TA]

mpg is effected by more than GR of the rear and engine size.

Tire size and wheel weight factors in too. Now with low gears and tall tires you may not be effected in mpg as you would with high gears and tall tires. There are gear ratio calculators to help you figure out what rpm you will be at and vice versa.



Most LS1's with T56's or 4L60E transmissions get on average 20-26 mpg, M6's with a light foot in rpms and staying on interstate at 70 mpg you could get as high as 27mpg.

Now that is all with it all being stock in parts and tune.


Having a LS1 in a Jeep is nothing to be embarrassed about, hell some of us think it's pretty damn cool. No purest snobs on here.

[362cuinxh]

Thanks. I understand about calculating for gears. Been doing gears for a long time. And tire weight affecting milage too. But that is mostly around town where acceleration is a factor. What I am interested in is a target RPM. Right now I am at about 2200 rpm at cruising speed. However there will be an increase in tire size bla bla bla. Also, as I understand it, these engines were designed to be able to have a decent amount of torque at low rpm to achieve better milage, at least on paper for the CAFE boys

[SMWS6TA]

My setup is a 403ci, T56, 8.8 rear with 411 gears on 275/45/R17 Nitto tires.

1st is almost a joke as well as mpg now. I'm lucky to get 18-20 mpg on Interstate on long trips. In town....well I didn't build it to be mpg economical.


On interstate in 6th gear at 70mph my rpms are around 1900, at 80mph (my usual cruising speed) it's around 2300.

But I'm not know for having a light foot on the gas pedal either.

[362cuinxh]

That is helpful. I understand the T56 has a pretty tall overdrive. My current overdrive ratio in the 4L60E is 30%, which is pretty tall in comparison to other Jeep overdrives of around 14% in the Auto. Will keep this tranny, I beefed it up and it has never had anything except Redline synthetic in it. Aux thermostatically controlled fan mounted on the cooler in the hood too

[SMWS6TA]

There's some issues with the 4L60e. They don't handle high torque loads well. Either it's 2nd or 3rd gear that prematurely seems to go out on them. The stock cooler configuration that comes on the f body has it running thru the radiator IIRC, most get an aftermarket cooler and reroute it thru that and have better cooling temps for the tranny.

[362cuinxh]

There are more issues than the 2nd gear. Can't remember the name of it, but there is a crown shaped thing that holds two of the planetaries in the rear. That and the tail shaft have been upgraded. Also kevlar band and clutch packages. In theory at least it is stronger. Also, tstat on the cooler fan is at 160°. I haven't ruled out the possibility of a 4L65E with the extra clutch disc in 2nd gear. All my good parts will swap over

[362cuinxh]

That reminds me, let me pic your brain a little more. There are LS2s available for the same price. More HP. Like I say sometimes, HP is like sex. More is better and too much is just right So my question is, does the LS2 have the same bell housing as the LS1?

[SMWS6TA]

Yes. If you want a easier block to get a hold of look for 5.3's (there's a ton out there, but make sure it's a 5.3 and not a 4.8). However for me the best block to get is a 6 liter LQ4 or 9 from 99-04 yrs. Pre 99 have the LT1 crank (different length then LS crank by about an inch) and 05< have 58x reluctor wheels so you will either need to get a convertor box ($$$$$) or get a 24x reluctor wheel and have it pressed on by a shop. It is far cheaper then the convertor box.

GEN III and IV engines share the same structure so most parts are able to be used on both.

My reasons I favor the LQ4/9 6 liter blocks are many; they handle more hp, N20 and boost over aluminum, they can be bored out more over aluminum, you can use LS3 heads and intakes, the starter mount doesn't break off like some LS1's have had done. Only negatives I found are they are heavier and you will either need to drill and tap a hole for the alternator or do like me and relocate it to the passenger head like turbo guys do.

[362cuinxh]

That is useful info. One of the reasons I wanted to go to the LSX is the aluminum block. Weight is an issue off road as well as for the street. The fact is, I have added weight and will add more when I change axles to accommodate the LS. With armor and stuff it is easy to have a 5000# Jeep. Something I am trying to avoid. For instance, I built my bumpers out of aluminum. Front winch bumper and skid for instance is only about 65#. There will be more Al stuff added in place of steel. The goal is to stay below 4000#, not easy to do. Whatever I do, the motor will probably stay stock. Let's face reality, a rock crawling suspension rides nice on the street and off road, but is not a good candidate for excessive HP. However I have some tricky upgrades to compensate somewhat for that. Have done one already. Think about the potential for wheel stands with a soft suspension with 14" of travel. Might be fun a couple of times, but it would get old fast.

[SMWS6TA]

Then I suggest a 5.3 for your build. They have plenty of power and torque for what your looking to do. Most are aluminum but there are a few iron blocks out there.

While the LS2 will have more power potential it's IMHO not worth the added cost over the 5.3.