4L65E won't go into overdrive
Thread Starter
Staging Lane
Joined: Jan 2014
Posts: 52
Likes: 0
From: GA
4L65E won't go into overdrive I have a stock LS2 (plus headers) and stock 4L65E in my '74 Nova. The drivetrain was pulled from an '06 GTO with 38k miles. I'm using the Dakota Digital dash replacement gauges, so at present time I don't have a gear shift indicator (because I didn't realize that was an extra cost item for the VHX gauges). So, when I shift into Drive, I do it by feel and sound.
The shift linkage is a Lokar cable because the stock setup wouldn't work with the engine/transmission/headers that I have. The linkage was professionally installed by a custom shop. The column shifter (yeah, I know) clicks easily up and down the gears, so the linkage seems to be OK.
Since getting the car up and running with the new drivetrain, only once have I seen it shift into overdrive. Every other time I'm hitting around 2k RPM at 40 MPH and closing on 3K RPM at 60 MPH with a 4.10 rear end and 26.6 inch tall rear tire. I know that's a steep rear gear, but I've done the calculations and comparisons with other cars. I should be seeing around 2200 RPM at 60, which I actually did see happen ONCE but can't duplicate.
When I start out, I shift very slowly from Neutral to Drive so as not to skip a gear. I'm careful for it to not click more than once past Neutral. But for some reason, I always end up limited to 3rd gear.
The tranny reacts in every other way just as I'd expect. Shifts good up the gears and down the gears, both at part throttle and full throttle. Shifts are smooth and not harsh.
The car was professionally tuned, but I'm a newbie to that kind of thing so I don't know what was done other than nixing the VATS and downstream O2 sensors. I don't know if the transmission settings were touched at all. I would guess the tire size and rear ratio had to be programmed in, but I don't have any way of knowing.
Oh, yeah, I've also tried, while driving, slipping the shifter over a notch toward Neutral to see if I missed a slot, but it goes to neutral. I'm stumped.
I don't have a tuner package, but I'm open to buying one and learning if that will help solve the problem. But, I don't know where to start looking. I don't want to drop the cash on a tuner package if I don't need it.
Where do I start?
The shift linkage is a Lokar cable because the stock setup wouldn't work with the engine/transmission/headers that I have. The linkage was professionally installed by a custom shop. The column shifter (yeah, I know) clicks easily up and down the gears, so the linkage seems to be OK.
Since getting the car up and running with the new drivetrain, only once have I seen it shift into overdrive. Every other time I'm hitting around 2k RPM at 40 MPH and closing on 3K RPM at 60 MPH with a 4.10 rear end and 26.6 inch tall rear tire. I know that's a steep rear gear, but I've done the calculations and comparisons with other cars. I should be seeing around 2200 RPM at 60, which I actually did see happen ONCE but can't duplicate.
When I start out, I shift very slowly from Neutral to Drive so as not to skip a gear. I'm careful for it to not click more than once past Neutral. But for some reason, I always end up limited to 3rd gear.
The tranny reacts in every other way just as I'd expect. Shifts good up the gears and down the gears, both at part throttle and full throttle. Shifts are smooth and not harsh.
The car was professionally tuned, but I'm a newbie to that kind of thing so I don't know what was done other than nixing the VATS and downstream O2 sensors. I don't know if the transmission settings were touched at all. I would guess the tire size and rear ratio had to be programmed in, but I don't have any way of knowing.
Oh, yeah, I've also tried, while driving, slipping the shifter over a notch toward Neutral to see if I missed a slot, but it goes to neutral. I'm stumped.
I don't have a tuner package, but I'm open to buying one and learning if that will help solve the problem. But, I don't know where to start looking. I don't want to drop the cash on a tuner package if I don't need it.
Where do I start?
TECH Junkie
Joined: Dec 2012
Posts: 3,620
Likes: 1,332
From: Iowa
You can buy a $20 BAFx obd2 scanner and get an app for your phone (I use dash command, but there are many others such as torque) to see if it is commanding 4th gear via the pcm or not. Might have to spend 10 or 15 bucks for the "extended parameters" on the app
If you have a buddy with a decent code scanner it should be able to do the same thing.
If you know anyone with a Tech-2 scanner, they can ride with you and manually command 4th gear and converter lockup with that tool. Similarly HP tuners can as well.
If you have a buddy with a decent code scanner it should be able to do the same thing.
If you know anyone with a Tech-2 scanner, they can ride with you and manually command 4th gear and converter lockup with that tool. Similarly HP tuners can as well.
Thread Starter
Staging Lane
Joined: Jan 2014
Posts: 52
Likes: 0
From: GA
So, I *may* have found the problem, but even so I still have a question. I was playing with the car today and I *SLOWLY* eased the shifter out of neutral. I felt the tiniest little click, and I stopped the shifter right there. This click was so small that I can see where I might have missed it before. I took the car out after this, and I was seeing about 2500 RPM at 60 MPH. An improvement for sure, but not what I think I should be looking at. I'm expecting about 2200 RPM at 60 MPH:
RPM = MPH * rear end ratio * 336 / tire diameter
60 MPH * 4.10 * 336 / 26.6 = 3100 RPM
Add in my 0.7 overdrive, and you get 2175 RPM
The 26.6 inch tire diameter is correct according to the manufacturer, and correct according to charts for the tire size I'm running on the rear (245-60R15). My only guess at this point is maybe the converter isn't locking up? That would account for a 200 to 300 RPM difference wouldn't it? And that's exactly what I'm seeing.
RPM = MPH * rear end ratio * 336 / tire diameter
60 MPH * 4.10 * 336 / 26.6 = 3100 RPM
Add in my 0.7 overdrive, and you get 2175 RPM
The 26.6 inch tire diameter is correct according to the manufacturer, and correct according to charts for the tire size I'm running on the rear (245-60R15). My only guess at this point is maybe the converter isn't locking up? That would account for a 200 to 300 RPM difference wouldn't it? And that's exactly what I'm seeing.
It's way more common to have a problem that keeps the tcc from locking.
Are you using a tcc unlock switch on the brake pedal? Thats a wire separate from the brake light circuit.
Most common is a slight misfire. I've seen live scan data show misfires that kept the tcc off yet wasn't there long enough to show a dtc.
Are there any dtc's?
Are you using a tcc unlock switch on the brake pedal? Thats a wire separate from the brake light circuit.
Most common is a slight misfire. I've seen live scan data show misfires that kept the tcc off yet wasn't there long enough to show a dtc.
Are there any dtc's?
Thread Starter
Staging Lane
Joined: Jan 2014
Posts: 52
Likes: 0
From: GA
I don't have a scanner to see trouble codes. It probably makes sense for me to go ahead and spring for an HP Tuners package. I could see what's going on as well as be ready for playing around with tuning for myself.
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Thread Starter
Staging Lane
Joined: Jan 2014
Posts: 52
Likes: 0
From: GA
I stumbled on the answer to this problem, and I'm a little surprised no one suggested it:
Out driving the car this past weekend and stumbled across one of those radar speed signs that shows your speed. I was doing about 41/42 at the time, and the sign was flashing between 46 and 47. A 5 MPH difference would definitely cause some wrong RPM readings. So, I put my VHX gauges in calibration mode and made several runs against the radar between 40 and 50 MPH. I purposefully set the car about 1 MPH off (so it says I'm going faster than I really am), but it's still close to a 5 MPH difference from previous.
Now the RPMs are just about dead on what I would expect. Seems there's no transmission problem after all.
Out driving the car this past weekend and stumbled across one of those radar speed signs that shows your speed. I was doing about 41/42 at the time, and the sign was flashing between 46 and 47. A 5 MPH difference would definitely cause some wrong RPM readings. So, I put my VHX gauges in calibration mode and made several runs against the radar between 40 and 50 MPH. I purposefully set the car about 1 MPH off (so it says I'm going faster than I really am), but it's still close to a 5 MPH difference from previous.
Now the RPMs are just about dead on what I would expect. Seems there's no transmission problem after all.
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TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
Thread Starter
Staging Lane
Joined: Jan 2014
Posts: 52
Likes: 0
From: GA
But, we could trade spars forever and never declare winner. Truth is, we both got bit by the same bug - making assumptions without availability of all the data. You guys assumed I had a fully sorted car and was just trying to fix a tranny bug. I assumed the shop that wired up my gauges set the speedo correctly. We should have more closely followed the scientific method. Hopefully, that's good learning information for those who happen on this thread in the future.