Torque Converter/Rear Gear
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Torque Converter/Rear Gear I just got my car to the track for the first time last week and overall it went pretty well but my 60ft is not what it should be. I talked to a couple experienced guys and they both seemed to think the car acted like the converter was too tight. I am going to put a camera in the car for next time out to see what the tach shows to see if the converter needs work. This also brings me to my next question. I am considering going from a 4.10 rear to 4.56. What would be the best tuning approach for me to take? Should I get the converter right with my current gear and then consider the gear change if needed or would different gears require different converter setup?
The car would 60ft from 1.38-1.41 with pretty consistent 6.10 ET but had a best trap speed of 119 mph and a few 115-116mph runs. I'm just thinking that with that speed if the car will 60ft it should be easily in the 5s. I was leaving off the transbrake and tried different launch rpms from 3k-5k and didn't really change anything. Traction is not an issue because I'm running 32x14.5w.
The car would 60ft from 1.38-1.41 with pretty consistent 6.10 ET but had a best trap speed of 119 mph and a few 115-116mph runs. I'm just thinking that with that speed if the car will 60ft it should be easily in the 5s. I was leaving off the transbrake and tried different launch rpms from 3k-5k and didn't really change anything. Traction is not an issue because I'm running 32x14.5w.
Last edited by WV Z06; May 29, 2017 at 08:08 AM.
Converters are built to what you are actually running. So any big changes will need a converter change. I would get a converter built for the setup you are going to run with and see what it does.
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I should add that the car had 60ft times of 1.26-1.28 with previous owner with a hydraulic roller 408 that should have made less power than my engine so I am relatively confident the converter is some of my issue. If the converter needs to be tuned to whole setup and if it is going to give me a better ET then I would rather do gears first and not pull converter twice.
I'm very new to drag racing and am just not sure what the gear change will do.
Im assuming this is a nitrous engine. The gear should help it 60ft. But there are lots of factors. When is nitrous coming on? Can you bring it in faster? Pulling timing at launch? Ect. Sounds like you know whats going on with the engine and making it run well. Rpm is going to tell you a lot. Would be nice if you can log the runs.
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Im assuming this is a nitrous engine. The gear should help it 60ft. But there are lots of factors. When is nitrous coming on? Can you bring it in faster? Pulling timing at launch? Ect. Sounds like you know whats going on with the engine and making it run well. Rpm is going to tell you a lot. Would be nice if you can log the runs.
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Being the fact that you went from 3 to 5000 rpm on the launch, with no change, and you know for a fact, that you are dead hooking. I would have to say that you are blowing through the converter. I would start with a custom converter speced to your combo. It will make a huge difference. Going to a 4:56 gear I would have to ask you, what is your tire size, and how high you can spin it, if your going 1/4 mile. But if your going 1/8 mile, do it before you get the new converter, because they will need to factor that in.
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Being the fact that you went from 3 to 5000 rpm on the launch, with no change, and you know for a fact, that you are dead hooking. I would have to say that you are blowing through the converter. I would start with a custom converter speced to your combo. It will make a huge difference. Going to a 4:56 gear I would have to ask you, what is your tire size, and how high you can spin it, if your going 1/4 mile. But if your going 1/8 mile, do it before you get the new converter, because they will need to factor that in.
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Oh, I didn't notice the tire size in your first post. I would definitely get at least 4:56 gears. But If your mostly doing 1/8 mile, you might even want to go 4:88. Not sure what rpm you would be turning in the 1/4 though. I like Yank billet race converters. You wont get a better 60ft. But that's just my opinion. PTC, Circle D, Neil Chance, Coan, and several others are very good too. Whoever you order it from, will need a lot of info on your car. Trans type of coarse, Weight, HP, Gearing, Flywheel brand & part#, tire size, and a few more things. Im not sure about the others, but Yank put an extended snout on so you don't need that spacer for the flywheel. When you get the converter it is imperative to make damn sure you check the space between the flywheel and converter pads (when the converter is pushed all the way into the trans). It has to be right. I cannot stress this enough!!! Close, will not cut it. So do it, right after you tighten the bell housing bolts, just in case you have to pull it back apart, if its too close. If its too far, you can use shim washers to get it right. Ours ended up being perfectly in tolerance. Prolly why he wanted to know what brand and part# on the flywheel.
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Oh, I didn't notice the tire size in your first post. I would definitely get at least 4:56 gears. But If your mostly doing 1/8 mile, you might even want to go 4:88. Not sure what rpm you would be turning in the 1/4 though. I like Yank billet race converters. You wont get a better 60ft. But that's just my opinion. PTC, Circle D, Neil Chance, Coan, and several others are very good too. Whoever you order it from, will need a lot of info on your car. Trans type of coarse, Weight, HP, Gearing, Flywheel brand & part#, tire size, and a few more things. Im not sure about the others, but Yank put an extended snout on so you don't need that spacer for the flywheel. When you get the converter it is imperative to make damn sure you check the space between the flywheel and converter pads (when the converter is pushed all the way into the trans). It has to be right. I cannot stress this enough!!! Close, will not cut it. So do it, right after you tighten the bell housing bolts, just in case you have to pull it back apart, if its too close. If its too far, you can use shim washers to get it right. Ours ended up being perfectly in tolerance. Prolly why he wanted to know what brand and part# on the flywheel.
If you can datalog your passes, it will help the converter manufacturer dial in the converter much more effectively. A video only does so much but seeing the actual stall when launching, driveshaft speed, shift rpm and drop between gears is priceless when getting a converter specked out. If you have G-force data it will make it that much better. If you do not have a data logger, I would spend the money on one before making any changes.
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If you can datalog your passes, it will help the converter manufacturer dial in the converter much more effectively. A video only does so much but seeing the actual stall when launching, driveshaft speed, shift rpm and drop between gears is priceless when getting a converter specked out. If you have G-force data it will make it that much better. If you do not have a data logger, I would spend the money on one before making any changes.
I am not sure what PCM you are running now or if you are running a computer. Racepak makes stand alone dataloggers if you are running a carb. I am running FAST XFI 2.0 and it has all the datalogging functions that are needed. If you are running a factory PCM, I am sure there are some software options that are available but I am not sure what the best ones are at this time. I have used HP tuners datalogging and it seemed to have everything needed except for a wideband input but that was years ago so they might have an interface now.
what rpm are you crossing at now? with the current converter and 4.88 gears you may just find a killer combo that still lets you cross below 7800 on top of 1/4.
if you only ran 1/8th then gear for that .
if you only ran 1/8th then gear for that .
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Crossing at 6500-6600 in the 1/8. After seeing the video of the tach the converter is definitely on tight side so we are going to open it up some and see what it does. If that doesn't get me where I need to be I may try the gears. And I probably will try the 4.88.
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I'd say 1k-1200. I'm going to open the converter some and shift it higher. After watching the video it's pretty evident this engine likes rpm. I think I'll end up having to do gears too but I think the converter will definitely help and it's the cheapest and easiest thing for me to try right now.
Last edited by WV Z06; Jun 10, 2017 at 09:45 PM.
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Being that you will mostly be running the 1/8, and all motor only, I would go 4:88. I'm assuming you have a solid lift motor and should be able to spin it pretty high. You should be okay in the 1/4 too. It will help the glide make the jump to high gear. I would do that first then recheck what your converter is doing. You may be fine.