The following is a compilation of posts I made in the automatic section but I'm not sure if it's tuning. File is attached at the bottom.


Hey guys, I was tuni ng a friend of mine's car the other evening. It's kinda nasty, 408" iron block, 243/246 112, AFR 205s, etc. It has a built 4l60e, Vig stall rated 3200 but flashes 4300 on his setup, stock 3.23s in the 10-bolt and hard radials that protect the tranny and make it a spin machine It's a 1998. It had a tune from a previous h/c 346 and told me of the problem before tuning. Oh yeah, it WILL downshift to secon gear properly.

As I got into the file, lots of the shift/mph tables had been changed. Having done this plenty before I eyed all of the part throttle and WOT tables back out but the issue persisted. I then loaded back all of the stock tables from an OEM 1998 A4 for shift MPHs globally and it still has the issue. Here is the tune of you want to see it. Basically only things non-stock in the tranny section are tq mngmnt, shift time (250mSec to disable adaption), and lockup tables to only allow lockup in 4th gear, etc.


it accurately says what gear we are in; I can't log much else, maybe it's a 98 thing. At 15 MPH it makes a lightest throttle shift into 3rd, and at 19 MPH when floored it will not kick down, even though as it moves to a WOT downshift table for that, it should be allowed at 31 MPH or less according to it AND the part-throttle table at 100% TPS. The TPS is functioning properly as well.

No idea who built the tranny or what's in it.

Also, a downshift can be forced by pulling back the shifter OR I can even force it through my VCM Scanner software's special control section.

It's wierd, if you are in the valid range to kick back to second, it will, but if it's in second, third, or fourth gear, and the downshift SHOULD go back to first, it won't downshift at all, it'll stay in the gear that's it's currently in.
I'll put the file here but I think it's something physical. Any ideas?

 

??...

 

Good luck. Trans tuning seems to be a weak point on all the boards. I have a friend who's car won't shift 1-2 if shifted manually, but works perfect any other time. Noone seems to be able to figure that out either. Sorry for no good info in my post.

 

I would look at it for you, but i would need the file in a bin or efi format.

 

I don't have an old enough verison of HPT to pull a binary

 

Frost, has the VCM previously been tuned with ls1edit? I remember a problem from a while back that didn't show up in any of the tables, but a complete reflash (not just calibration) fixed it. I have no idea what the actual cause of the problem was, but since a total rewrite fixed it, it must have involved a corrupted total vcm rewrite. I'm sure a mechanical problem is not yet out of the question, but thought I would throw out another possibility.

 

Yeah it has, and I haven't tried a write-entire yet, but I'll give it a shot!

 

oh gosh...here we go... he is gettin her on the road... this is gonna get interesting (lol, don't mean to hijack thread or anything)

 

no luck, back ttt

 

GOT IT.... Bill of HPT fame and glory pointed to this for a similar issue for another user and it fixed me as well...

The car in question had a LARGE cam... idled in the the 66-69kPa range at best!

Turns out the issue is a stupid stock TPS range checking table and for some reason seems to only affect 98 models.... Here's the culprit table for P0121:

 

Glad to hear that was the fix!

That pesky p0121 can be the cause for all kinda crap from abs malfunctioning to shifting pattern oddities.

Ya gotta love when a little tuning can fix what seemingly might've been a tranmission issue

 

why have only seen this on this 1998? None of the following years seem to have this issue...