Hi all,

OK it's fair to say that I'm getting a tad nervous about the TJ - since its new to us and after that oil leak I found the other day.

I like to use Cruise Control as much as possible (we live in the country); so I had set it at 100 K's but had slowed down in an 80 K section of highway and then turned a corner. When I selected Resume - of course the tranny wanted to get back to 100 K - and (as they do) it downshifted to get on with the job.

Instead of being a smooth downshift, it was more of a "thump" and then on again without issue? Anyone had similar experiences, or know what it's likely to be? :eh:

Cheers

Steve

I've noticed the cruise control is a bit impatient in trying to get the car back up to speed. Uses way too much throttle, more than I like. So I get the car up to cruise speed with the right foot and then select resume. Much smoother and avoids that downshift followed by an upshift.
Doesn't help with the thump, though.
I've noticed on my 4 speed TL the shifts can be rough if you lift off or press on the throttle just as it does a shift. Took a while to find the right spot where the throttle doesn't need to move in going from 0 to 60, only lifting up at 60 in 4th. Smooth changes that way.
Try simulating the action of the cruise control in going from 80 to 100, ie mash the throttle (not all the way as you are likely to end up in second) when in fourth and see if you get the same sort of thump or a smooth shift when it changes back to third. This will tell you if it's the cruise control or the gearbox.

I have had this issue with my series 2 TJ since i bought it nearly six years ago. It will also do it if driving without cruise control and hit the accelerator a bit harder than normal. All other shifting is absolutely perfect and always has been. I get around it by accelerating gently from 80kph. If it does drop back to third, it then does it normally.

I've noticed the cruise control is a bit impatient in trying to get the car back up to speed. Uses way too much throttle, more than I like.



Doesn't help with the thump, though. So - are you you getting that thump too??



Try simulating the action of the cruise control in going from 80 to 100, ie mash the throttle (not all the way as you are likely to end up in second) when in fourth and see if you get the same sort of thump or a smooth shift when it changes back to third. This will tell you if it's the cruise control or the gearbox.

OK - will do. I can see a trip to a trans specialist in the not too distant future. Judging by an article that one of the guys posted here very recently; one of the very first things they do (if they're good) is test drive it looking for bad habits - and I don't like this one! :mad:

Steve

I have had this issue with my series 2 TJ since i bought it nearly six years ago. It will also do it if driving without cruise control and hit the accelerator a bit harder than normal. All other shifting is absolutely perfect and always has been. I get around it by accelerating gently from 80kph. If it does drop back to third, it then does it normally.

Thanks TJ - so it's a solid thump?

Steve

FWIW I've had some ongoing issues with rough shifts on my KL, especially at lower speeds, and a recent in-place clean of the TB and vent ports using carbe cleaner made a big difference, really smoothed it out. It makes me suspect an issue with the operation of the ISC.

I'm about to have the TB properly cleaned and the ISC replaced, so will report back on the results of that.

By way of comparison, my KH always has had very smooth shift, not really aware of them unless u listen to the RPM or the occasional minor thump that everyone gets under certain conditions, so I don't think harsh shift is acceptable in these cars. (yes I know that they are different cars and boxes in many ways, but these days I think it's a reasonable expectation that the auto shifts smoothly, we're not talking about 1970's clunkers here).

Of course there could lots of reasons for a harsh shift, I'm only sharing my experience here.

So - are you you getting that thump too??

Not tried the cruise resume under your conditions so I wouldn't know.
Learnt long time ago automatics all have their quirks and the driver needs to adapt to the way the gearbox does things to keep it at it's best behaviour as far as smooth shifts go.
Magna 4 speeder doesn't seem to like throttle changes while it's thinking about an upshift or downshift from my experience and can thump a bit. Easy to live with, but of course a manual doesn't do that.

I'm about to have the TB properly cleaned and the ISC replaced, so will report back on the results of that.

Thanks KW,

For the uninitiated - what the hecks the TB and the ISC?? :kb:

Cheers

Steve

Thanks KW,

For the uninitiated - what the hecks the TB and the ISC?? :kb:

Cheers

Steve

I'm guessing at Throttle body for TB....?

ISC - Idle Speed Control. Due to the way it works, if it is dirty it may affect non-idle operation.

Yes the thump mine has always had is a solid thump. It now only happens on rare occasions due to teaching myself to not let it happen. I recently had my auto flushed and refilled and no nasty bits were detected in the fluid.

ISC - Idle Speed Control. Due to the way it works, if it is dirty it may affect non-idle operation.

It does idle a bit too high in my opinion? Settles eventually.

Steve

Try simulating the action of the cruise control in going from 80 to 100, ie mash the throttle (not all the way as you are likely to end up in second) when in fourth and see if you get the same sort of thump or a smooth shift when it changes back to third. This will tell you if it's the cruise control or the gearbox.

OK, took the car to work last night. In CC at 100 K's it does thump on the change to 3rd. Switched CC off and at first I though the thump was better, but another couple of attempts had me still uncertain. I tried just a few attempts at various speeds i.e. 80 K's and there was a bit of "thumpiness" :happy:

Hard to say overall - regular upshifts are nice and smooth, just these downshifts!

Steve

check ur engine mounts, it may be the engine rolling back on shift and then dropping down back onto the rubber/or lack of...

check ur engine mounts, it may be the engine rolling back on shift and then dropping down back onto the rubber/or lack of...

Thanks Trotty - I will take another look, but at least one of them looked really healthy the other day. Still I'm aware they can be cracked/split through.

Cheers

Steve

Mine will thump if cruising in 4th for a while on say the freeway and suddenly kicking down to 3rd to overtake. Seems like it gets caught by surprise or something. Love to know cause too.

If you want a real thump then drive along at 40 then plant your foot. Dropping to first is like hitting nitrous :P then it shifts to second and you hit your head on the steering wheel due to lack of power. Same goes for @ 100km/h, plant it so it drops to second..

+1 for engine mounts. I've got one thats obviously gone (the rubber is all shredded etc) and my idle is kinda rough as well.

Start the car, and tug on the accelerator cable, and see if the engine does anything weird, like moving abnormally etc.

If you want a real thump then drive along at 40 then plant your foot. Dropping to first is like hitting nitrous :P

:clap: Hey Scorcher, haven't tried it - sounds great though!

Must say as a really recent owner of a TJ 3.5 I'm really lovin' the power these things have! Sad that I've given it to the wife for the dogs really. Now I'm really drooling over the idea of owning a 380, but financially that will have to wait (a long while it appears)!

:think:

Steve

Guys,

I cannot yet swear to this - but I may have found a solution for a "thumpey" auto-trans. I noticed a product that Nulon had that is called Automatic Transmission Treatment (http://www.nulon.com.au/products/Specialty_Products/Auto_Transmission_Treatment/#.UQM_jR0m3ng) - so I gave it a shot and (nervously) applied it to the tranny!

I've just driven around 90 K's with it in there and the trans does seem quite a bit smoother - better still though; when I deliberately try to kick it down to get it to thump - it does not!

Early days indeed, but if that's all I need to do then I'm happy! :happy:

Steve

Is that Nulon stuff compatible with Mistu transmission fluid?

I think it has PTFE in it . . . .

Is that Nulon stuff compatible with Mistu transmission fluid?

I think it has PTFE in it . . . .

It does have PTFE in it, I'm not sure what effect it has on SP-III fluid though

Ptfe is "compatible" with sp-3 but the word compatible gets thrown around a fair bit when it comes to transmissions.

Is that Nulon stuff compatible with Mistu transmission fluid? I think it has PTFE in it . . . .

The MSDS sheet is showing that it contains less than 10 percent PTFE, so less than 30 mls of the 300 ml container. Hey - all I can say is that my trans is now so smoooooooth! :happy:

Steve

my TJ was exhibiting this shift behaviour for about the last year. then my ISC shat itself outright. i replaced it 5 days ago and try as i might i cannot get the symptom to recur. In fact all the shifts are smoother