Transmission slips, then slams into gear - Diesel Forum

korey · 11-17-2009, 02:03 PM

Ok, I posted this same post on powerstroke.org and the general consensus was that this is all being caused by my chip. I'm posting here for a second opinion before I drop more money on a DP tuner.

"Ok heres the situation,

Got a 2000 7.3 with a little over 160k on it. Its had a crappy 60hp superchip chip that stayed plugged into the PCM most of its life, and was driven very easily. The truck was given to me about 12k miles ago and and I ditched the superchip in favor of an edge evolution shortly after, and was really happy with it. The only thing I noticed was that when merging onto the highway either 2-3 or 3-4 (I forget) would slam really hard, so I called edge and they told me to firm up that shift, which I did and the problem went away. Forward to about 2 weeks ago, trans starts to do the slamming again but only on the extreme mode on the chip. And only the 2-3 shift when getting on it. Then it got really bad and starting doing the slamming all the time. So I thought maybe it was the chip and plugged it into my computer to do a firmware update. This seemed to make it better for a couple days. Then out of no where it got horrible, when you are driving with more than just a little bit of throttle the transmission slips and then literally bangs into gear. I have no idea what it is, but it only does it in the race and extreme modes. Stock and tow seem a little bit firmer than they should be, however. Not sure what is causing this, trans temps are about 160ish (live in south florida) most of the time and the trans fluid is full and looks good. Anyone have any ideas? I would really appreciate any legitimate help."

**caryt** · 11-17-2009, 02:13 PM

Crappy tuner get a TW chip..but damage to your trans has more than likely happened...

korey · 11-17-2009, 02:55 PM

I'm just going to go with a DP, hopefully the trans isnt damaged since it drives fine on stock and my trans still has a low temp

tattoocharlie · 11-17-2009, 08:17 PM

is your o/d light flashing?if so its thrown codes,that will point you in the right direction.i had similar issues,i had the edge installed,when removed the problem still persisted.it was intermittent.i had a stuck 2-3 shift valve,i rebuilt my valve body all is well.

korey · 11-17-2009, 10:06 PM

Nope, no codes and no flashing OD light

Pepp33 · 11-18-2009, 05:16 PM

Get a BTS. Your tranny is done! My truck is doing the same thing going from 2nd to 3rd. Sometimes it doesn't shift as hard. Scheduled a BTS tranny for Dec.
2000 F250 7.3 205,000 miles

**Flywheel** · 11-18-2009, 06:55 PM

You might have broken springs in the valve body....

korey · 11-18-2009, 09:12 PM

The only thing that confuses me about the trans possibly having broken springs in the valve body, is that it doesn't do it on the stock setting of the chip.

tattoocharlie · 11-19-2009, 12:10 AM

im not a 4r100 expert but i dont believe a chip could cause a slip in your tranny.if im correct(took a tranny class years ago)slippage is due to low pressure(ie not engaging clutches fully)due to stuck valve,bad seal on clutch drum,or even excessivly worn clutches and the clearance is out of spec.i believe the chips can affect shift points,etc.i think if you drove it for awhile without the chip you would find the problem will show itself.if you had a stuck valve it would allow a pressure drop,or a broken spring the valve will not function properly.if it were mine id take out the valve body,run through it,new sonnax valves springs etc.....you can get all the parts for right around 100.00.

AGAIN I AM NOT AN EXPERT......I DO HAVE A BASIC UNDERSTANDING OF TRANSMISSIONS,MOSTLY OLDER GM AND MOPAR,BUT ALTHOUGH ALL SLIGHTLY DIFFERENT,THEY ALL WORK ON THE SAME THEORY.

tattoocharlie · 11-19-2009, 12:12 AM

also i wouldnt drive it until you figure it out,slipping is not good for the clutches.

**Mark Kovalsky** · 11-19-2009, 06:06 AM

Quote:

Originally Posted by tattoocharlie

im not a 4r100 expert but i dont believe a chip could cause a slip in your tranny.

A chip could set the trans pressure too low and that would cause the trans to slip.

Since it is doing it in the higher power settings but not in the stock setting I'm leaning towards the chip IS causing the problem.

tattoocharlie · 11-19-2009, 05:14 PM

And There You Go.......mark Is The Man

phlorit · 03-24-2010, 11:40 PM

I know this is an old post, but I have to ask a question. I have a recently rebuilt 4r100 in my 1996 F250 4X4. The transmission seems fine, but every once in a while it really shifts hard between 3rd and 4th. But other times it is pretty smooth. During hard acceleration, its pretty harsh. Rattles the truck a bit. All my friends think there is something wrong. The trans builder stated they put in a mild shift kit, some extra beefy bands and what not. I thought this may cause a harder shift. The truck is stock otherwise and not chipped at all.

it does not slip really, just shifts hard. Goes into first from Park like normal. It defiantly shifts quick and tight, not sloppy at all.

Also one other thing, sometimes I need to let off the throttle to get a shift from third to fourth with out forcing the shift.. With a mild shift kit, does this seem normal?

Towed 7500lb trailer for 400 miles this weekend and no issues... just a hard shift once in a while. Thanks in advance for any help!