Lost 4th gear

Ever since my 4t65 install I have been unable to get the car to stay in fourth gear when throttle is applied. When I take my foot off the gas at highway speeds, it falls into 4th and stays there until I A) apply throttle or B) slow down enough to where it has to downshift on its own.

I am wondering if you have thoughts as to what could be causing this? I know its not mechanical as the entire trans is fully built up. I dont think its electrical either cause my wiring is right. I think its in the tune somewhere.

What are your thoughts? Ive just been driving it as is, and despite the shifter being in OD, it stays in 3rd unless I the conditions are as listed above. Gas mileage takes a beating, but with the high performance 2500 stall and trans cooler, heat really is never an issue.

My cruise control also doesnt work, and I think that is related.

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Ever since my 4t65 install I have been unable to get the car to stay in fourth gear when throttle is applied. When I take my foot off the gas at highway speeds, it falls into 4th and stays there until I A) apply throttle or B) slow down enough to where it has to downshift on its own.

Are you sure it's shifting out of 4th gear? Have you verified with a scan tool? Reason I ask, your TCC may disengage, raising RPM and making it seem like you are in 3rd, when you are in 4th. Another way to test this - when you are in the throttle in 4th, and it seems like it downshifts, keep your foot on it and manual select 3rd with the shifter. Does anything (RPM) change? If you were truly in 3rd gear, there should be no change in RPM.

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I am wondering if you have thoughts as to what could be causing this? I know its not mechanical as the entire trans is fully built up. I dont think its electrical either cause my wiring is right. I think its in the tune somewhere.

Have the shift tables been changed using tuning software?

yes, i know for a fact that it is staying in 3rd at highway speeds. Whether in OD or 3rd, the RPMS are the same. The difference is that in OD, the car will downshift and RPMS drop when you let off the gas. In 3rd the RPMS stay high since it is holding 3rd gear.

Weird right?

The shift tables WERE changed since the gearing went from 2.92 stock (I believe) to I think its 3.73 or something when I added a HD LSD to the transmission.

I have actually had fourth gear ONCE, when driving on the highway. It happened right after reinstalling my AC system and went for a test drive. Of course that didn't last long. Theory on that is some wire back in the pit (firewall area) of the engine bay. But there is nothing back there I can think of and I have not been able to recreate that scenario. In fact I just fixed the AC AGAIN 2 days ago and was working in that area and still didnt recreate the scenario.

Another problem is I have not been able to get the powertuner to work on my Vista desktop. I am actually having my brother in law install a dual boot for XP tomorrow just so I can get my tuner to start working again.

hells bells, just got the tuner to work on vista again. going to try to post my bin that is currently in the car PCM

any ideas on how to do that? its been so long

There should be a BIN somewhere that was used to program the PCM. You can email the BIN file to me, or post it up at a file sharing site for download. If you can't find the BIN, you can try extracting it from the PCM, but I've never gotten that to successfully work.

I am just blind....i got it, sending email.

Is there an "email" button listed below my sig?

email sent with attached bin...
thx aaron

All of your shift lines are still stock, which wouldn't cause your 4-3 shift problem. Only program change I've found is the wheel pulses per rev, and pulses per mile, which were probably set to compensate for the gear ratio change. Does your speedo read correct?

I believe it is still correct. Yes those two parameters were changed for the gear change. I've continually been told that the fourth gear problem is because the range switch B wire is not working. The range selector under the speedo flashes. But when I got fourth to hold that one time, it was still flashing and I can get it to read OD occasionally and it still wont hold fourth.

I tried manually grounding that range B wire and still no good. Is it possible my PCM banks are all good except the one bank for the range switch B wire?

Drew,
Mine does the EXACT same thing.
I noticed it after i had mine rebuilt.
On the highway when im on the gas it stays in 3rd until i let off the throttle. Even 5% TPS will keep the car in 3rd.
When im using cruse control it still does the same thing. Stays in 3rd until the car goes down a hill (TPS goes to ~0) and it will upshift to 4th.

Would be nice to find a fix for it, but i think its something mechanical.

I did have the trans go shift kit installed and the guy increased the line pressure of my trans.
Also i am using a "tuned" black ring shift modulator which may have something to do with it.

Matthew

Mr.Riviera wrote:

Drew,
Mine does the EXACT same thing.
I noticed it after i had mine rebuilt.
On the highway when im on the gas it stays in 3rd until i let off the throttle. Even 5% TPS will keep the car in 3rd.
When im using cruse control it still does the same thing. Stays in 3rd until the car goes down a hill (TPS goes to ~0) and it will upshift to 4th.

Would be nice to find a fix for it, but i think its something mechanical.

I did have the trans go shift kit installed and the guy increased the line pressure of my trans.
Also i am using a "tuned" black ring shift modulator which may have something to do with it.

Matthew

Do you have a 4t60 or 4t65. Ill be royally pissed if its mechanical. This builts 65 cost me a fortune and was torn apart after a couple hundred miles cause I cracked the original core (my fault). The trans guy still claims everything inside is new and fine. All solenoids were replaced.

Maybe the shift kit is the culprit?

I have a 4t60 still.

When you scan it while driving, have you seen a peak in pressure that perhaps correlates to the shift problem? Im gonna try this when I get my tuner working unless you've covered this already.

And who rebuilt your trans? A friend or shop, etc?

dreww wrote:

And who rebuilt your trans? A friend or shop, etc?

A race shop in town did it.
All new parts, race converter, shift kit, hardened 4th and 2nd clutches, and modified shift modulator.

Mr.Riviera wrote:

dreww wrote:

And who rebuilt your trans? A friend or shop, etc?

A race shop in town did it.
All new parts, race converter, shift kit, hardened 4th and 2nd clutches, and modified shift modulator.

What did they say about the problem?

didnt ask.
I attributed the issue to the shift kit or vac modulator.

When i first got the car back it wouldnt go into 4th at all and i took it back to the shop. They pulled the trans and said the 4th gear solenoid was slightly bent so they replaced it. He said he didnt originally replace it because it looked good, but when he took a micrometer to it he noticed it got damaged when my chain broke.

I emailed zzp to see if they've ever encountered such a problem with all their experience. They said they haven't and to return the car to the transmission shop.

Update, got fourth gear today. Dunno how long it will last but it only did this once months ago. So strange.