Premature Transmission Failure

[RETed]

I have been having far too many transmission failures for the power my engine is making and the type of driving that I typically do. I have some theories, but I thought that I would run them past all of you.

There is a long history below, this is the executive summary:
NA and turbo transmissions failing
Suspect advanced ignition timing / misfiring.
Problem did not occur with factory ECU/tune/flywheel.
Also think that the lightweight flywheel is contributing factor
Shifter has small vibration (can only be felt if held in hand, does not shake visibly).
Shifter vibration gets significantly worse if timing is advanced further.
Shifter vibration goes away if timing is retarded 15 degrees.
Vibration does not occur above 4,000 RPM or below 1,500 RPM.
Engine pre-ignites in vacuum if AFR is richened past 15:1 with existing ignition timing.

If you want further details, read below:




In the last 3 years and 30,000ish miles, I have put 5 transmissions in my '86 GXL. To give a summation of the failures:
The original transmission was replaced before I owned the car.
The transmission that was in the car when I got it had no synchros in 2nd or 5th, but otherwise was fine for almost 30,000 miles of my ownership.

I found that advancing the timing about 10 degrees past stock greatly improved my fuel economy. Leaning the fuel out by tweaking the AFM helped power, but made no mileage difference (running on the O2 sensor either way). Then I replaced the ECU with a Haltech E6x. I replaced the transmission at the same time because I had no synchros in 2nd or 5th.

With the Haltech ECU, I advanced the timing as far as I could go (which was about 65 degrees BTDC, as I ran a base advance of 15). This improved my average fuel economy from 26 MPG to 34 MPG (19x,xxx mileage 6-port). I was also able to eek an additional 17 Whp out of it (per the G-tech - from 138 WHp to 155WHp, from 95 WLb-Ft to 101 WLb-ft).

Unfortunately, this was the beginning of the transmission woes.

The 1st transmission that I put in (when I replaced the ECU and wiring harness) was a $50.00 special I got on eBay - it seemed to be Ok when I put it in. This transmission lasted for about 6 months (5,000 miles). The synchros were all fine, but the bearings went out of it (I let it go until it would squeal in 5th gear under throttle). I also installed a light-weight flywheel at this time.

Transmission 2 was a 'known-good' transmission from a friend. It lasted for about 6 months (3,000 miles) although this was more spirited driving than before. The failure was the same, good synchros (except 2nd, which I killed drag racing) but bad bearings (I replaced the transmission when it started howling in neutral). I had this transmission in the car when I dynoed at 155 WHp.

Transmission 3 was installed when I upgraded to a 4-port engine. I had a hunch that I would need to upgrade the drive train too, as I was going to install a turbo on the 4-port, so I bought another $75.00 eBay special. This transmission was making noise after 750 miles back of the 4-port. I ran it for about 3,000 miles until I smoked the clutch on the dyno. That dyno run I made 160 WLb-Ft with the 8.2:1 CR 4-port (I was starting to be concerned for my drive train after the clutch gave out).

I should also note that I broke a side seal when I assembled this engine, so it had a side seal that was 1 inch short in the front rotor. It made good compression on two faces of that rotor, but one face was weak. This made the engine shake at idle. I put it down to the porting and never thought another thing of it, until I pulled the engine down to steal the apex seals for another build (it was sitting in my garage) and found the broken seal, with the rest of the groove full of carbon and that rotor face nearly black, while the other 5 were very clean.

The next transmission that I installed was a Turbo II transmission, J-spec. This transmission appeared to be in good shape when I put it in the car. It lived for 10,000 miles back of the 8.2:1 4-port. After about 5,000 miles, the synchros on 5th gear actually broke, they didn't wear out, as they worked fine one shift and the gears ground on the next shift. In addition, I lost the ability to get the shifter into reverse. I eventually got reverse working again, but there were no synchros in 5th or reverse. This transmission started making noise while I was still tuning the 4-port, but made significantly more noise after the dyno run (to make sure that the drivetrain power loss was the same from NA to turbo drivetrain - it was identical). The bearings got so bad toward the end of that 10,000 miles that I had trouble shifting.

The next transmission I installed was from a guy in Minnesota, who said it was in good shape (it appeared to be). This was a US spec (0.72 overdrive instead of the nasty 0.8) turbo transmission. I installed the 9.2:1 4-port engine at the same time (no miss/shake at idle). I also installed a Haltech E8, so I had to redo my fuel and timing curves (although I started and broke the engine in on the old E6X, as it is unpleasant to start a freshly-rebuilt rotary with a new ECU).

My timing curves were conservative for about 4,000 miles, until I ran the engine at the dyno, when I advanced the timing to peak power. I had overheating issues, so I couldn't go past 6,000 rpm, but made 162-182 WLb-ft (I think that the speed reading on the dyno was incorrect, although the dyno reported 182 WLb-ft@5400 rpm, my trace from my ECU showed that I had run to 6000 RPM). I had no trouble with the transmission.

I ran the engine for another 2,000 miles and installed the Defined Autoworks Headers and my own custom exhaust. This netted over 10 WLb-ft on the g-tech, but it was too late in the season for another dyno run by the time I figured the overheating problem out.

Anyway, I put about 4,000 miles on and I noticed this transmission making noise, but only at full throttle/high speed in 3rd and at heavy throttle and any speed in 5th gear. It was still quiet while idling. However, I made some adjustments to idle ignition timing to allow me to run the engine more lean at idle and it occasionally misfires at idle now (I am running on the O2 sensor, 14.8:1). Just Yesterday, I noticed a whine at idle when the transmission is hot. Obviously this is concerning, as this is Transmission #5!

I decided that it can't be torque that is killing the transmissions, as this engine probably only makes 180-185 WLb-ft max - even with the Defined Autoworks headers - and most turbo guys are breaking that, even with relatively stock setups (that is only about 225 Lb-ft at the engine - about 275 Hp in the turbo world of 7,000 RPM red-line). There must be something else.

Here is my theory: I think that it is advanced ignition timing and a light-weight flywheel (old-school racing beat, 12lb) that is killing the transmission. I think that the early ignition is generating negative torque and that this is putting the gears and bearing through reverse loading, causing the roller and ball bearings to lose their oil film and to wear out prematurely. I am going to put the chamber pressure transducers back in as soon as winter breaks (had to park the car yesterday for winter) and see how early the pressure spike is reached. I had the timing advanced on the old stock ECU, but I had a stock flywheel.

The Racing Beat flywheel (which I have had for a long time) came off a turbo build from a while back, it was significantly heavier than the Fidanza NA flywheel that I had on while the NA transmissions were dying like flies.

The vibration can no longer be felt with the engine spinning above about 4,000 rpm and it is no longer noticeable below 1,500 rpm (the timing is running about 18 deg BTDC @ WOT at that speed). Shaking starts again at high throttles while under 900 rpm, but it is normal lugged engine shaking.

I tried taking timing out at 2,000 rpm and the vibration went away at this speed, then started again as the engine accelerated towards 2,250 rpm. I retarded the ignition about 15 degrees to make the vibration stop, but the range was about 300 rpm, so 10 degrees would probably have been sufficient if I had taken it out across the board.

Sorry about the LONG post, but I wanted you to have the same information I have. I won't be able to test any theories for a while, as the salt trucks are out, which means the car doesn't leave the driveway and the vibration doesn't happen unless I have been driving for a little (oil in transmission warmed up?).

EDIT: I should add that I have 2 >6,000 RPM WOT trigged Data logs in my ECU in the last 3 Months. I have not been driving this car hard lately - certainly not in 5th gear (which makes the most noise).

[NoDOHC]

I have been having far too many transmission failures for the power my engine is making and the type of driving that I typically do. I have some theories, but I thought that I would run them past all of you.

There is a long history below, this is the executive summary:
NA and turbo transmissions failing
Suspect advanced ignition timing / misfiring.
Problem did not occur with factory ECU/tune/flywheel.
Also think that the lightweight flywheel is contributing factor
Shifter has small vibration (can only be felt if held in hand, does not shake visibly).
Shifter vibration gets significantly worse if timing is advanced further.
Shifter vibration goes away if timing is retarded 15 degrees.
Vibration does not occur above 4,000 RPM or below 1,500 RPM.
Engine pre-ignites in vacuum if AFR is richened past 15:1 with existing ignition timing.

If you want further details, read below:




In the last 3 years and 30,000ish miles, I have put 5 transmissions in my '86 GXL. To give a summation of the failures:
The original transmission was replaced before I owned the car.
The transmission that was in the car when I got it had no synchros in 2nd or 5th, but otherwise was fine for almost 30,000 miles of my ownership.

I found that advancing the timing about 10 degrees past stock greatly improved my fuel economy. Leaning the fuel out by tweaking the AFM helped power, but made no mileage difference (running on the O2 sensor either way). Then I replaced the ECU with a Haltech E6x. I replaced the transmission at the same time because I had no synchros in 2nd or 5th.

With the Haltech ECU, I advanced the timing as far as I could go (which was about 65 degrees BTDC, as I ran a base advance of 15). This improved my average fuel economy from 26 MPG to 34 MPG (19x,xxx mileage 6-port). I was also able to eek an additional 17 Whp out of it (per the G-tech - from 138 WHp to 155WHp, from 95 WLb-Ft to 101 WLb-ft).

Unfortunately, this was the beginning of the transmission woes.

The 1st transmission that I put in (when I replaced the ECU and wiring harness) was a $50.00 special I got on eBay - it seemed to be Ok when I put it in. This transmission lasted for about 6 months (5,000 miles). The synchros were all fine, but the bearings went out of it (I let it go until it would squeal in 5th gear under throttle). I also installed a light-weight flywheel at this time.

Transmission 2 was a 'known-good' transmission from a friend. It lasted for about 6 months (3,000 miles) although this was more spirited driving than before. The failure was the same, good synchros (except 2nd, which I killed drag racing) but bad bearings (I replaced the transmission when it started howling in neutral). I had this transmission in the car when I dynoed at 155 WHp.

Transmission 3 was installed when I upgraded to a 4-port engine. I had a hunch that I would need to upgrade the drive train too, as I was going to install a turbo on the 4-port, so I bought another $75.00 eBay special. This transmission was making noise after 750 miles back of the 4-port. I ran it for about 3,000 miles until I smoked the clutch on the dyno. That dyno run I made 160 WLb-Ft with the 8.2:1 CR 4-port (I was starting to be concerned for my drive train after the clutch gave out).

I should also note that I broke a side seal when I assembled this engine, so it had a side seal that was 1 inch short in the front rotor. It made good compression on two faces of that rotor, but one face was weak. This made the engine shake at idle. I put it down to the porting and never thought another thing of it, until I pulled the engine down to steal the apex seals for another build (it was sitting in my garage) and found the broken seal, with the rest of the groove full of carbon and that rotor face nearly black, while the other 5 were very clean.

The next transmission that I installed was a Turbo II transmission, J-spec. This transmission appeared to be in good shape when I put it in the car. It lived for 10,000 miles back of the 8.2:1 4-port. After about 5,000 miles, the synchros on 5th gear actually broke, they didn't wear out, as they worked fine one shift and the gears ground on the next shift. In addition, I lost the ability to get the shifter into reverse. I eventually got reverse working again, but there were no synchros in 5th or reverse. This transmission started making noise while I was still tuning the 4-port, but made significantly more noise after the dyno run (to make sure that the drivetrain power loss was the same from NA to turbo drivetrain - it was identical). The bearings got so bad toward the end of that 10,000 miles that I had trouble shifting.

The next transmission I installed was from a guy in Minnesota, who said it was in good shape (it appeared to be). This was a US spec (0.72 overdrive instead of the nasty 0.8) turbo transmission. I installed the 9.2:1 4-port engine at the same time (no miss/shake at idle). I also installed a Haltech E8, so I had to redo my fuel and timing curves (although I started and broke the engine in on the old E6X, as it is unpleasant to start a freshly-rebuilt rotary with a new ECU).

My timing curves were conservative for about 4,000 miles, until I ran the engine at the dyno, when I advanced the timing to peak power. I had overheating issues, so I couldn't go past 6,000 rpm, but made 162-182 WLb-ft (I think that the speed reading on the dyno was incorrect, although the dyno reported 182 WLb-ft@5400 rpm, my trace from my ECU showed that I had run to 6000 RPM). I had no trouble with the transmission.

I ran the engine for another 2,000 miles and installed the Defined Autoworks Headers and my own custom exhaust. This netted over 10 WLb-ft on the g-tech, but it was too late in the season for another dyno run by the time I figured the overheating problem out.

Anyway, I put about 4,000 miles on and I noticed this transmission making noise, but only at full throttle/high speed in 3rd and at heavy throttle and any speed in 5th gear. It was still quiet while idling. However, I made some adjustments to idle ignition timing to allow me to run the engine more lean at idle and it occasionally misfires at idle now (I am running on the O2 sensor, 14.8:1). Just Yesterday, I noticed a whine at idle when the transmission is hot. Obviously this is concerning, as this is Transmission #5!

I decided that it can't be torque that is killing the transmissions, as this engine probably only makes 180-185 WLb-ft max - even with the Defined Autoworks headers - and most turbo guys are breaking that, even with relatively stock setups (that is only about 225 Lb-ft at the engine - about 275 Hp in the turbo world of 7,000 RPM red-line). There must be something else.

Here is my theory: I think that it is advanced ignition timing and a light-weight flywheel (old-school racing beat, 12lb) that is killing the transmission. I think that the early ignition is generating negative torque and that this is putting the gears and bearing through reverse loading, causing the roller and ball bearings to lose their oil film and to wear out prematurely. I am going to put the chamber pressure transducers back in as soon as winter breaks (had to park the car yesterday for winter) and see how early the pressure spike is reached. I had the timing advanced on the old stock ECU, but I had a stock flywheel.

The Racing Beat flywheel (which I have had for a long time) came off a turbo build from a while back, it was significantly heavier than the Fidanza NA flywheel that I had on while the NA transmissions were dying like flies.

The vibration can no longer be felt with the engine spinning above about 4,000 rpm and it is no longer noticeable below 1,500 rpm (the timing is running about 18 deg BTDC @ WOT at that speed). Shaking starts again at high throttles while under 900 rpm, but it is normal lugged engine shaking.

I tried taking timing out at 2,000 rpm and the vibration went away at this speed, then started again as the engine accelerated towards 2,250 rpm. I retarded the ignition about 15 degrees to make the vibration stop, but the range was about 300 rpm, so 10 degrees would probably have been sufficient if I had taken it out across the board.

Sorry about the LONG post, but I wanted you to have the same information I have. I won't be able to test any theories for a while, as the salt trucks are out, which means the car doesn't leave the driveway and the vibration doesn't happen unless I have been driving for a little (oil in transmission warmed up?).

EDIT: I should add that I have 2 >6,000 RPM WOT trigged Data logs in my ECU in the last 3 Months. I have not been driving this car hard lately - certainly not in 5th gear (which makes the most noise).