[activelydying]

hello all. i have a 99 4.0 auto with a problem. when driving, it starts out fine, but all of the sudden the engine just starts to rev like it got put in neutral. this will happen for a few seconds then all is well. any ideas.

 

[mrbigjeep]

you could have broken gear teeth. but thats just a complete guess.

 

[activelydying]

it doesn't happen all the time though, usually just in the morning or when starting for the first time of the day.

 

[Mudweiser]

Could be your bands are slipping in the tranny. Could be getting time for a rebuild. Ide definately check your fluid levels or have the tranny flushed out. Ever had the filter changed? or the tranny serviced? Could be something as simple as the torque converter not getting fluid on startup and needing to warm up. But it could be a sign of problems to come.

 

[activelydying]

having the tranny flushed, is that something that i could do. what filter are you referring to when you asked about changing.

 

[activelydying]

i have never had the tranny serviced, i've only the vehicle for about four months now and it has 71,000 miles. could it be about time to have it serviced.

 

[amerijeep]

You know, I always have heard that you shouldn't change the fluid in your auto tranny. However, I don't think you're going to be any worse off. Anyway, Your tranny is slipping. It is time for a rebuild. That's your best option. You don't want that thing to slip when you pull out into traffic os something.

I'd bet money that someone was hard on that thing before you got it.

 

[04moneypit]

You know, I always have heard that you shouldn't change the fluid in your auto tranny. However, I don't think you're going to be any worse off.
I'd bet money that someone was hard on that thing before you got it.

I'll agree with the second part of the statement. But, changing the fluid in an auto should be done from 24-36000mi (depends on manufacturer recommendation), sooner under harsh conditions. If the fluid gets hot it reduces it's capacities to function properly. A fluid and filter change with some lucas oil tranny fix (this stuff is magic) might help you out and for roughly $35, this is cheaper than taking it to a tranny shop for an evaluation, where most will tell you to have a rebuild done for average cost from $1000-2000. I'd spend the $35 first and see if it helps.

 

[activelydying]

ok i'm a moron. what filter is everyone speaking of. there's a filter for the tranny?

 

[4Jeepn]

1st check fluid level, when jeep is up to temp. Fluid should be pink. Filter is in the tranny pan, just look under the jeep for the big cookie sheet under the tranny. This is removed to get to the filter and change the fluid. Most of the oil change places only pump the old fluid out, which can cause issues as all the crap the filter got is now sucked back into the system. The proper way is to remove the pan and drain it out and replace the filter if needed.

You said, it starts out fine, but then does it. Does that mean within a min or two or 10-15 mins down the road?

 

[Scotty355]

Yes there is a tranny filter, located directly on the bottom of the trans. It is a messy job due to no drain plug, I would recommend changeing the fluid first and if you do decide to do it yourself remove all bolts from cover except for 1 last one, loosen last bolt and pry opposite end of cover down and hope to not make to big of mess.

 

[activelydying]

it usually does it within a few minutes after starting. it starts out fine leaving the driveway and everything, but usually once i get on the street and start to give it a little gas it misses. it seems like it happens as it tries to switch to second gear.

 

[4Jeepn]

it usually does it within a few minutes after starting. it starts out fine leaving the driveway and everything, but usually once i get on the street and start to give it a little gas it misses. it seems like it happens as it tries to switch to second gear.

Assuming the fluid level is okay. Try letting it warm up for a few minutes before heading out next time. Also see if shifting up from 1 to drive does anything when you start out, any funny sounds etc, rpm go up etc. etc. another thought, is eveything think connected to the throttle body okay?

 

[activelydying]

there aren't any funny sounds except coming from me. the rpm only go up because my foot is still on the gas before i noticed that it didn't change gears. once it does switch gears it jerks pretty hard. i was thinking the throttle body may have been the cause for the problem, but i thought that would happen constantly not just starting up.

 

[04moneypit]

OK, so your rpm is up because you are on the gas. Are you flooring it, or on it pretty hard? If you are really pushing the gas hard it will stay in first because the auto has a kickdown, or passing sensor that will drop it down into a lower gear or keep it in low to get the rpm's higher before shifting to keep it in the power band. Does it upshift as soon as you let off the gas? If so, the passing gear could be what's happening. As mentioned before, changing your fluid is a messy job. The only way to make it easier is to install a pan with a drain plug. The filter is going to be right inside your trans after you remove the pan. It is usually silver and flat like a pancake. If you change your fluid, go to an auto parts store and get a replacement filter first, then you will know what it looks like. Some are held in place with a bolt, others just have a push/pull connection that you just pull the filter out and slide another into place.

 

[activelydying]

no, i'm not on the gas that hard. i would say just normal driving. i think i just notice the rpm shooting up because i'm not moving just coasting and i can hear the engine. as soon as i get off work( just another 45 hours), i'll probably do some searching under the vehicle, then off to auto zone. thanks a lot for all the help.