Multi-Part Question - Transmission Clunk

Was heading home from Blacksburg today when I started feeling a very hard "clunk" when shifting from 2nd to 3rd. As I was on the front end of a 5 hour trip I thought it would be a good idea to do a little research, so I pulled up vehicross.info on the BlackBerry and learned about the likely culprit, something that seems to be interchangeably referred to as the transmission mode switch, range sensor, neutral safety switch, or SWITCH ASM; PO in the OEM parts catalog. All seem to refer to part #8-96017-511-0, and it looks to be about $150 from Merlin or IsuzuParts.com. Seems like a straightforward fix, but the experience today left me concerned about something else.

As coincidence/luck/fate would have it, I picked up a used Auto Trans Interceptor module from Marlin on Friday, and was planning on installing it at some point down the road. Before I bought it I did some research here and most comments indicated that you get much more "crispness" when accelerating, but at the cost of slightly "rougher" shifting. Originally I was okay with that, but after this weekend without the Interceptor installed, I'm a little more worried. So here are my main questions at this point:

(1) Should I go ahead and order the switch and have it replaced, or is there a chance that the existing part might just need to be cleaned, adjusted, etc.?

(2) Does the Interceptor create the same level of clunk that I experienced due to (we'll assume for now) a faulty neutral safety switch? What happened today felt like something breaking, not better performance. If that's the feel I'll get with the Interceptor, interested parties can start sending me PMs now.

(3) For those members that have Interceptors installed, what values did you set for the line pressure and torque converter delay? How hard (if at all) does your tranny clunk when shifting vs. OEM?

Thanks guys!

Transmission mode switch is fairly easy to inspect and clean or replace from what I gather. I looked into it when running into shift probs. I'd start there. If you open up the switch and all looks good, then move on to other fixes.

Don't ignore the obvious such as fluid levels.

I think I can answer all of those for you.

First... the clunk you are experiencing needs to be repaired before installing the Interceptor (I think you figured that already.).

You are correct in the diagnosis... Mode Switch. I've replaced 3 now (different VX's).

There IS a way to clean it and adjust it. If you want to go that route, please search for that thread. I like to make sure the thing won't fail for (hopefully) the duration of my ownership, so I buy new. (Totally your call).

Once repaired, if you install the Interceptor, you can induce a "similar" slamming effect by adjusting the POT too far one way... but when you adjust it right (lots of tune, drive, tune, drive...) you will get a result like the following:

Stock: revvvvv, shiffffffft, in gear.
Interceptor: revvvv, shFT, in gear.

(I know, my analogies are kinda strange.)

I hope this helps.
If you need further assistance or explanation, let me know. I have your same setup on my VX.

---JIM---

Thanks guys. SilverBullet I think I will take your advice and just replace it, I had already read the cleaning how-to on the Planet and it looked a little too advanced for my taste. I'm with you, I'd rather just replace it and (hopefully) not have to worry with it again.

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Originally Posted by SilverBullet75

Once repaired, if you install the Interceptor, you can induce a "similar" slamming effect by adjusting the POT too far one way... but when you adjust it right (lots of tune, drive, tune, drive...)

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So do you have a recommended setting? My concern is I'd rather NOT have to take the skid plates off and put them back on more than once if possible. Plus I really would rather have a mechanic install it, so obviously I don't want to keep going back in for adjustments (though they're nice guys and would probably do it for free - unless the skidplates have to go on/off each time). Surely the dials on the Interceptor are marked in someway, 1-10, 10/20/30%, etc?

And yes your analogies are weird but strangely they do make sense. :)

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Originally Posted by vt_maverick

Thanks guys. SilverBullet I think I will take your advice and just replace it, I had already read the cleaning how-to on the Planet and it looked a little too advanced for my taste. I'm with you, I'd rather just replace it and (hopefully) not have to worry with it again.


So do you have a recommended setting? My concern is I'd rather NOT have to take the skid plates off and put them back on more than once if possible. Plus I really would rather have a mechanic install it, so obviously I don't want to keep going back in for adjustments (though they're nice guys and would probably do it for free - unless the skidplates have to go on/off each time). Surely the dials on the Interceptor are marked in someway, 1-10, 10/20/30%, etc?

And yes your analogies are weird but strangely they do make sense. :)

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I remember reading that another member made an extension for the harness on the interceptor and mounted it in cab, thats what I would do, especially with the skid plates under there.
That gives the ability for anytime adjustments. It would not be hard at all to do...
As for the clunking, mine was doing that after an Isuzu tranny maintenance. I did nothing about it, 6 months later(about 2k miles), I had no 3rd to 4th shifting unless I let off the gas, and then it started thunking into first. I would get it fixed ASAP.

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Originally Posted by Marlin

I remember reading that another member made an extension for the harness on the interceptor and mounted it in cab, thats what I would do, especially with the skid plates under there.
That gives the ability for anytime adjustments. It would not be hard at all to do...

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Funny I was having that same thought this morning. Damn I should have that electrician guy who sold me this thing do it before I bought it. :mad: :p I do think that's the way to go, although I probably would just put it in the engine bay somewhere.

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Originally Posted by Marlin

As for the clunking, mine was doing that after an Isuzu tranny maintenance. I did nothing about it, 6 months later(about 2k miles), I had no 3rd to 4th shifting unless I let off the gas, and then it started thunking into first. I would get it fixed ASAP.

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That's my other sneaking suspicion, I just had the shop do the 60K maintenance which included a tranny flush and filter replacement, so maybe they messed something up? In any event I thought it would be wise to have the replacement part on hand if they need it, especially since it seems like this is a bound-to-fail-eventually part. I did "ground" the VX for the week, I'm driving the wife's Axiom to work all week while we wait on the part to arrive (hopefully Thursday so I can get it fixed on Friday).

Make sure that the shop filled the transmission correctly. There is a pretty involved process of warming the trans up, shifting through all the gears, letting it cool down, standing on one leg, reciting the alphabet backwards all while wearing a brightly colored clown wig.

OK, maybe not all that, but there is a very specific set of steps that have to happen to make sure that the fluid is topped off. Other members have had their transmissions fail because these steps weren't followed by the shop they used.

The instructions may be in the how-to section, or maybe someone who has them on hand will post them up.....if you need them.

Thanks, I'll definitely have them check the fluid level when I take it in. I tend to think a low fluid level would cause a consistent problem though right? I mean it happened consistently during a 20 minute drive to lunch yesterday, then a five minute drive to the gas station immediately thereafter, but then not again for the next 5 hours (meaning it hasn't come back). Now I worry that it will work perfectly when I take it into the shop and they'll wonder why we're even doing this...

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Originally Posted by vt_maverick

Funny I was having that same thought this morning. Damn I should have that electrician guy who sold me this thing do it before I bought it. :mad: :p I do think that's the way to go, although I probably would just put it in the engine bay somewhere.



That's my other sneaking suspicion, I just had the shop do the 60K maintenance which included a tranny flush and filter replacement, so maybe they messed something up? In any event I thought it would be wise to have the replacement part on hand if they need it, especially since it seems like this is a bound-to-fail-eventually part. I did "ground" the VX for the week, I'm driving the wife's Axiom to work all week while we wait on the part to arrive (hopefully Thursday so I can get it fixed on Friday).

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I now know there is no way they did my maintenance correct. It took em like 30 minutes. I don't think they filled it IAW the procedure.

Well got the part in today and made an appointment at the garage tomorrow to have them replace it. Discussed the problem with them over the phone and they made the same guess before I even mentioned already having the part in hand. They're going to replace it tomorrow and box up the old one for me, in addition to checking fluid levels and anything else that might have gone wrong. Once I get the current switch out I'll compare it to the "dirty" switch pics in the other thread to see if maybe it can just be cleaned. If so I'll list it here for anyone who's interested.

Just got the call from the shop, the switch was definitely the problem, they found trouble codes specific to it in the computer. Have to get me one of those scan gauge do-dads, that way I don't have to buy parts on pure faith in our tribal knowledge. ;) But it's still hard to beat the forum for quality recommendations.

Thanks to everyone for their opinions! :thumbup:

Oh one more thing, I skipped installing the Interceptor for now, figured I'd give it at least a few weeks to make sure the switch replacement went well before adding something else into the mix.

Marlin - How far do you think you could extend the wires without having a negative effect on, what's the word, damn it, can't remember my physics/electronics class... maybe conductance? I don't really want the thing out in the open, but having it inside the glove box sounds like a smart idea, what with the skid plates and all.

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Originally Posted by vt_maverick

...having it inside the glove box sounds like a smart idea, what with the skid plates and all.

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Hey if for no other reason - having it in the cab would sure make the initial adjustment easier. Beats having to get out and crawl under (or pop the hood if installed there) over and over and over and over!

Before mine burnt on my exhaust I had the line pressure at 10% and delay on full or close to it 90%? Make sure you secure it well or you may burn yours too. Once you get it set right you won't need to change again so in cab is not necessary. The only time I messed with it was when racing 1/4 mile at the track I would up the line pressure to maybe 20-30%

The higher you set the line pressure the harder the downshifts will be but it will shift faster on upshifts... adjust until it all runs smooth enough for you.

If you decide to sell, I would like it. I loved the feel of the shifts once you had it set right.

Not sure why but I had an IM tech make me take it off once to pass inspection FYI

Thanks Alaska, finally got somebody to answer the settings question... was beginning to think I was going to have to start a new thread. :) No plans to sell it right now, but I will definitely PM you if I try it out and don't like it. But from everything I've heard and read I think I will be happy (assuming I can get the settings right in less than 100 tries).