4.0 on 33's struggles to go past 60 mph

Sensei

TJ Enthusiast
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4.0 on 33's, 3spd auto, 4.56 gears. Jeep has "trouble" going past 60-65 mph. If I do manage to get to that speed, i'm roughly sitting at 3100-3300 rpms. The jeep also makes a sort of "whining" noise whenever i'm at around 50 mph and start putting 45%-65% pedal pressure to start increasing the speed to the 60's. I have a pretty decent diagnostic tablet I can use to look at the live data, and I believe the torque converter may not be locking up. There is a data point in there that is named "Torque converter desired position" and my result always seems to be "Unlocked". That doesn't seem right. Also my rpms will sometimes bounce down to 2900 at the speeds I previously described, before jumping back to the original cruising rpms it was just at (I don't necessarily feel this drop in rpm while driving, no lurching forward from sudden cut of rpm, speed seems to stay the same). The transmission seems like it never wants to downshift also. I can be going 50 mph and hit an uphill slope, causing my speed to decrease to the low 40's, I mash the pedal to 80-100% pressure and the trans just does not want to downshift. It stays in third. Also when I approach a stop, and then start again, the trans always starts in second gear. I have to press the accelerator atleast 40% from a stop to get it to downshift to 1st again, where it shifts back to 2nd before I even hit 10-15mph, sometimes slower. Any ideas :/
 
Clogged cats, are you getting allot of heat? Unlocked torque converter will give you more power and not less, higher gear ratio because fluid math and all. Whine could mean you've got some bad bearings sucking allot of power, after a drive is anything excessively hot? If it's sucking horsepower it'll generate allot of heat.
 
Clogged cats, are you getting allot of heat? Unlocked torque converter will give you more power and not less, higher gear ratio because fluid math and all. Whine could mean you've got some bad bearings sucking allot of power, after a drive is anything excessively hot? If it's sucking horsepower it'll generate allot of heat.

Good advice.
 
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What would be considered excessively hot? If I place my hand on the front exposed portion of the trans pan after a drive id probably get second degree burns....

Also, I can hear that same whining whenever the jeep begins traversing a long uphill portion of road, even if my pedal throttle is relatively depressed the same amount as when I was previously travelling downhill. Like when im travelling 60 mph downhill, and wish to keep the speed around 60 for the uphill portion, i'll hear that whining.

My jeeps "cruising" speed seems to be about 40-45 mphs at 2200 rpms. By cruising speed I mean it's the speed my jeep will travel with absolute minimum depression on the accelerator pedal (once at speed). 50-55 mph will be about 20-35% depression on the pedal. But trying to maintain 55+ requires quite a bit of constant force on the gas pedal. Atleast 40% depression, where this will increase to 60-90% depression when trying to maintain speeds at severe climbs. All without the transmission ever downshifting it seems.

The trans doesn't downshift when rolling through a light that just changed to green either. Ill approach a stop light at 45mph, slowing down, but then it changes green. At this point I'm maybe at 20-30mph, sometimes 5-15 mph, but my jeep will never down shift from 3rd unless I absolutely mash the gas pedal. Honestly im tired of this damned 3 spd auto transmission. I wish I had a manual :ROFLMAO:
 
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Clogged cats, are you getting allot of heat? Unlocked torque converter will give you more power and not less, higher gear ratio because fluid math and all. Whine could mean you've got some bad bearings sucking allot of power, after a drive is anything excessively hot? If it's sucking horsepower it'll generate allot of heat.

I thought the purpose of a locking torque converter was to maintain a 1:1 power drive ratio? So while the torque converter being unlocked gives me more "power", it still gives me a slower speed on the road while unlocked, and while failing to lock. Does the converter locking effect the engine rpm at all? Im wondering if the 200 rpm dip I mentioned earlier might be the converter trying to lock up, and failing to do so. Granted, I only see this 200 rpm drop when absolutely pushing this thing on the highway 60-65mph for 20+ minutes. I've never seen it any other time.
 
A locked torque converter reduces engine rpm by stopping slippage between the engine and transmission. Your TV (aka kick down) cable is what causes the transmission to downshift when you step down on the accelerator pedal. Is the TV cable connected? Is it adjusted correctly so there's no slack in the cable? The TV cable connects between the throttle lever on the valve body and the TV bracket at the rear of the transmission on the driver's side.

Is there enough ATF in the transmission? Its level can only be checked while the engine is running and the transmission is in Neutral. It must be at the full mark, a little overfilled is far better than being a little underfilled.
 
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A locked torque converter reduces engine rpm by stopping slippage between the engine and transmission. Your TV (aka kick down) cable is what causes the transmission to downshift when you step down on the accelerator pedal. Is the TV cable connected? Is it adjusted correctly so there's no slack in the cable? The TV cable connects between the throttle lever on the valve body and the TV bracket at the rear of the transmission on the driver's side.

Is there enough ATF in the transmission? Its level can only be checked while the engine is running and the transmission is in Neutral. It must be at the full mark, a little overfilled is far better than being a little underfilled.

I believe the kickdown cable is adjusted to proper spec. I did recently attempt to do this TV adjustment because of these symptoms, but unfortunately my adjustment had little effect. I took off the white plastic retainer thing for the cable, and then completely removed all slack (there wasn't really any), ensuring not to be engaging the throttle plate lever nor transmission shift lever whilst setting said adjustment, by reinserting the locking white plastic retainer.
 
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So maybe my issue is my torque converter isn't locking up?

No, or at least it's not the reason you struggle to maintain 60MPH. The difference in efficiency is notable enough for it to be very worth the automaker's time to put in a lockup torque converter, but on older automatics (like those found in the TJ) it will unlock anytime you give it more than light throttle.
 
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Clogged cats, are you getting allot of heat? Unlocked torque converter will give you more power and not less, higher gear ratio because fluid math and all. Whine could mean you've got some bad bearings sucking allot of power, after a drive is anything excessively hot? If it's sucking horsepower it'll generate allot of heat.

I have checked the transmission temperature after driving and it was sitting at 200-210 F
 
4.0 on 33's, 3spd auto, 4.56 gears. Jeep has "trouble" going past 60-65 mph. If I do manage to get to that speed, i'm roughly sitting at 3100-3300 rpms. The jeep also makes a sort of "whining" noise whenever i'm at around 50 mph and start putting 45%-65% pedal pressure to start increasing the speed to the 60's. I have a pretty decent diagnostic tablet I can use to look at the live data, and I believe the torque converter may not be locking up. There is a data point in there that is named "Torque converter desired position" and my result always seems to be "Unlocked". That doesn't seem right. Also my rpms will sometimes bounce down to 2900 at the speeds I previously described, before jumping back to the original cruising rpms it was just at (I don't necessarily feel this drop in rpm while driving, no lurching forward from sudden cut of rpm, speed seems to stay the same). The transmission seems like it never wants to downshift also. I can be going 50 mph and hit an uphill slope, causing my speed to decrease to the low 40's, I mash the pedal to 80-100% pressure and the trans just does not want to downshift. It stays in third. Also when I approach a stop, and then start again, the trans always starts in second gear. I have to press the accelerator atleast 40% from a stop to get it to downshift to 1st again, where it shifts back to 2nd before I even hit 10-15mph, sometimes slower. Any ideas :/

Have you tried manually shifting the trans? I would drive it and see if you can get all the gears by manually shifting the trans. I would also inspect the cat. If you install a vacuum gauge on the engine and monitor it. If it starts to drop while loosing power pull the cat and inspect.
 
Have you tried manually shifting the trans? I would drive it and see if you can get all the gears by manually shifting the trans. I would also inspect the cat. If you install a vacuum gauge on the engine and monitor it. If it starts to drop while loosing power pull the cat and inspect.

I can manually shift it fine using the 1st, and 2nd gear selectors. Revs up perfectly fine 3500+ rpms. But obviously I need to put it back into D to give myself access to the 3rd gear. So it goes back to auto shifting.

Also it doesn't really seem like I'm "losing" power. Yes the jeep slows down when I have to climb hills, but I think the issue is more inherent to the transmission not down shifting or locking/unlocking at the right times. Once I'm rolling atleast 20-30mph, the trans will almost never down shift into 2nd from 3rd even if I floor it.

I have two issues really. I have to seriously lay into the accelerator when attempting to go from 30 to 60+ mph, since the transmission never downshifts to 2nd once I'm past a certain speed even if I floor it to max. And the second issue is once I am travelling 50+ mph, I have to keep a constant 40+% pressure on the pedal. I don't think I could hold 70-75mph even if I was 100% pressing on the accelerator, nor do I necessarily want to try that.

Anyone else got a 3 spd with 4.56 and 33's? How fast is your jeep able to drive on the highway? And how easily does it maintain said speeds?
 
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How do I do this? Can I read live data from the o2 sensor?

Buy an O2 sensor plug from an exhaust shop. Drill and tap the center of it for 1/8"npt threads. Attach an air pressure gauge, 0-30 psi or similar, to the plug via a hose and some npt barb fittings. Unscrew upstream O2 sensor and replace it with the gauge. Start the engine and see what kind of psi you have at idle and at around 3k rpm. Try to be quick with the testing, otherwise you might melt the hose.

I have the exact same drivetrain, tire size and gearing as you. Mine was topped out at 70mph with the foot on the floor. I had about 30psi of back pressure at 3000 rpm. After gutting the cats it went down to 2-5 psi and driving it after it ran like a raped ape, 100mph is no issue now.
 
I can manually shift it fine using the 1st, and 2nd gear selectors. Revs up perfectly fine 3500+ rpms. But obviously I need to put it back into D to give myself access to the 3rd gear. So it goes back to auto shifting.

Also it doesn't really seem like I'm "losing" power. Yes the jeep slows down when I have to climb hills, but I think the issue is more inherent to the transmission not down shifting or locking/unlocking at the right times. Once I'm rolling atleast 20-30mph, the trans will almost never down shift into 2nd from 3rd even if I floor it.

I have two issues really. I have to seriously lay into the accelerator when attempting to go from 30 to 60+ mph, since the transmission never downshifts to 2nd once I'm past a certain speed even if I floor it to max. And the second issue is once I am travelling 50+ mph, I have to keep a constant 40+% pressure on the pedal. I don't think I could hold 70-75mph even if I was 100% pressing on the accelerator, nor do I necessarily want to try that.

Anyone else got a 3 spd with 4.56 and 33's? How fast is your jeep able to drive on the highway? And how easily does it maintain said speeds?

The three speed definitely likes to lug around in 3rd. I adjusted my TV cable four clicks tighter after getting it set with no slack to try and make it hold second longer, it helped a bit, but not a ton. You just have to drive with enthusiasm to get it to use 2nd well. The best part is, you only have three speeds, so no matter how you drive it, the mileage always stays the same, about 11 for me, so why not give it some throttle.

We are both geared one step deeper than the factory equivalent for 33's, so we've got a bit of extra torque at the cost of top end speed. You should be able to maintain highway speeds with ease, and accelerate up almost all but the steepest of hills.

Check your cats next and I bet you'll find your problem.
 
The three speed definitely likes to lug around in 3rd. I adjusted my TV cable four clicks tighter after getting it set with no slack to try and make it hold second longer, it helped a bit, but not a ton. You just have to drive with enthusiasm to get it to use 2nd well. The best part is, you only have three speeds, so no matter how you drive it, the mileage always stays the same, about 11 for me, so why not give it some throttle.

We are both geared one step deeper than the factory equivalent for 33's, so we've got a bit of extra torque at the cost of top end speed. You should be able to maintain highway speeds with ease, and accelerate up almost all but the steepest of hills.

Check your cats next and I bet you'll find your problem.

I have the 32rh and 4.56 with 35s,I just got back from Denver with it barypulling itself ,got it home and still won’t go over 3000 rpm ,checking cats and will get back to the thread
 
Buy an O2 sensor plug from an exhaust shop. Drill and tap the center of it for 1/8"npt threads. Attach an air pressure gauge, 0-30 psi or similar, to the plug via a hose and some npt barb fittings. Unscrew upstream O2 sensor and replace it with the gauge. Start the engine and see what kind of psi you have at idle and at around 3k rpm. Try to be quick with the testing, otherwise you might melt the hose.

I have the exact same drivetrain, tire size and gearing as you. Mine was topped out at 70mph with the foot on the floor. I had about 30psi of back pressure at 3000 rpm. After gutting the cats it went down to 2-5 psi and driving it after it ran like a raped ape, 100mph is no issue now.

How did you stop the Cel light after gutting the cats?
 
Buy an O2 sensor plug from an exhaust shop. Drill and tap the center of it for 1/8"npt threads. Attach an air pressure gauge, 0-30 psi or similar, to the plug via a hose and some npt barb fittings. Unscrew upstream O2 sensor and replace it with the gauge. Start the engine and see what kind of psi you have at idle and at around 3k rpm. Try to be quick with the testing, otherwise you might melt the hose.

I have the exact same drivetrain, tire size and gearing as you. Mine was topped out at 70mph with the foot on the floor. I had about 30psi of back pressure at 3000 rpm. After gutting the cats it went down to 2-5 psi and driving it after it ran like a raped ape, 100mph is no issue now.

Holy shit this makes me want to go cut my cat off right now lol. I have a compression tester tool for my engine, so I just need to build that dummy o2 sensor you suggested and see what my readings are. Will report back. Thanks!