Which converter?

moldman05

Well-Known Member
Joined
Jan 27, 2006
Location
Rocky Mount NC
Destroyed torque converter in my buggy. Had transmission rebuilt and wanted a higher stall. Used a 6 cylinder converter. It’s still too tight. Engine pushes thru the brakes when I’m on some rocks trying to crawl back and forth. This is compounded by engine computer that won’t let it idle slow under load so I have to use neutral a lot and bump reverse or drive. I called TCI for advice for a 2000 stall. I now have a 1700 stall. They recommended a 2200 to 2400. Book calls it 1000 over stock. Wouldn’t that be 2500? It’s lot of work changing it out so I want to get it right. Engine is crate 502 with turbo 400,Atlas 3:8,diffs are 5:13 ,43” tires on 3800 lbs. I got enough motor that I should not have to be reving high but I want it to be smoother.
 
I've always selected torque converters that stall at the peak torque of the engine. According to the GMPP website, the crate 502 produces it's peak torque at 3600 rpm. Personally, I wouldn't choose one less than 3000 rpm. While I understand that the rule I'm going by is typically used in race or street/strip applications, I think it is applicable here as well. One must consider as well that when a 4x4 is engaged in low gear, the RPM stall of the torque converter is effectively lowered. Some argue that it's cut in half, but I don't quite believe that...

All that being said, I would be afraid at all of going with a 3000 RPM converter. 2500 would definitely be better than what you've got, though. But given your gear reduction and weight, I'd definitely be looking closer to 3k.
 
You spelled "clutch" wrong.

Lol...
 
Without a doubt in the world I can suggest calling PTC, answering their questions and then giving them 16 digits, an expiration date and 3 digits on the back.
Wait a week and receive a heavy box of goodness.
My money is on about a 2800-3000 stall for your build.
 
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NC-V said:
How high does it idle? and will it idle lower/does it just idle high because of the FI?
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Idle is about 750. Computer will adjust timing to prevent as they put it lugging. So when shifting back and forth from forward and reverse idle will be over 1000 till it settles down
 
Can you not tune that out on the computer? Or figure out some way to make the computer not see the load? It seems like it would be easier to make it idle more steady/consistently than going to a higher stall.

Seems like a high stall would cause more heat, and then once it really grabbed you’d go from nothin, nothin, bam you’re blowing the tires off. I’ve only dealt with higher stall converters in LS powered hot rods and that was over 10 years ago so I don’t know a great deal about them.
 
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77GreenMachine said:
Can you not tune that out on the computer? Or figure out some way to make the computer not see the load? It seems like it would be easier to make it idle more steady/consistently than going to a higher stall.

Seems like a high stall would cause more heat, and then once it really grabbed you’d go from nothin, nothin, bam you’re blowing the tires off. I’ve only dealt with higher stall converters in LS powered hot rods so I don’t know a great deal about gen.
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I can't really speak for the tuning aspect, since I'm just getting started with learning it...I'm assuming that the engine is sensing the load via manifold vacuum, and it probably adjusts the IAC to compensate.

The higher stall "can" create more heat, but doesn't always. Of course, it can be well compensated with a good cooler system and obviously a trans temp gauge for monitoring. I'm sure those are things already installed on his rig.

But what you've described is a huge misconception of high stall converters. There are many that think they only engage or "grip" at their advertised stall, which is never the case. I've currently got what presumably was a 4000 RPM stall converter in my TH350, because I ran it behind a healthy 383. I'd bet my 401k that it won't stall that high with my current engine, as the torque peak is lower in the RPM range, my gears are different, and the weight is much less than it was previously. But what I will contribute to your comment is that it under no circumstances would only grab at 4000 RPM...I could put it in gear and idle around under no throttle. It would drive right up onto my trailer with little effort. Sadly, that is the only incline I've ever tried to climb (so far...:rolleyes:), but it will work fine below that range. Basically what the advertised stall means is that it is a range in which the converter will "flash" to, or "foot brake" to, given a particular torque input from the engine (along with weight, tire size, gear ratio, etc. etc.)

Example: sitting at a stop, put the transmission in gear, and mat the throttle. You'd see the tach flash up to (or near) the advertised stall as the vehicle launches. Same thing with the advertised "foot brake" stall -- you could step on the brakes and the gas, and the tach will go up reasonably near the advertised stall. The "foot brake" stall is typically lower than the flash stall. But the vehicle will still idle and "creep" just fine, nearly the same as it would have with a stock converter...especially with the transfer case engaged in low gear.

But the purpose of a high stall torque converter is to eliminate engine lugging, just as @moldman05 described his is doing.
 
What he said....stall, flash, and coupling are all different.
 
When driving it, there it too much coupling at too low of a rpm.

Foot braking in high range, with as hard as I could push the pedal, it pushed thru the brakes at 1700 rpms.

But it will move at high idle speed in low range

The idle speed increase when dropped into get due to ECU thinking the Rpm’s are dropping then it advances timing, opens iac to speed engine.

Also factory cam for zz502 so some overlap with poor map signal at low rpm, the manual even says it won’t due well with lugging the engine at low rpm.

I think it needs a higher stall so that there is less coupling at idle speeds so less load to “lug” the engine down at idle and cause high idle condition.

This supposed to be a mid range stall converter but very little difference over the previous converter that had unknown specs.

Having trouble trying to figure out what stall to even try.

My dads other rig has a higher stall converter that under foot brake won’t push through the brakes until 2600 rpms, but feels like it wastes a lot of energy just to move.

That converter feels too high to me, but won’t move in gear at idle, which makes crawling easier bc it takes so much throttle just to get the rig to move.

Huge difference between the two rigs. Current one is the 4K lbs rig with 5.13s 3.8:1 atlas, and 500hp.

Old rig is 6k lbs, 5.13s, and 2:1 205 and probably 250 hp.
 
I know you and Scott @Mac5005 are the intellectual types, but trust someone who has been drinking the PTC Kool Aid for years.
PTC is one call and done.
The converter in my truck is some sort of voodoo stuff. Stalls higher under heavier engine loads. Like around 3200-3400 in high and around 2600 in low. Temps hang around 170* even going up to Mason Jar, non-stop.
Don't waste your efforts with Summit "whatever inch", Saturday Night Special converters. Been there, done that and pulled the transmission again shortly thereafter.
 
Jody Treadway said:
Don't waste your efforts with Summit "whatever inch", Saturday Night Special converters. Been there, done that and pulled the transmission again shortly thereafter.
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This. I did the same thing -- went through the Summit/Jegs catalogs a few times, swapped converters in my TH350 a few times trying to get it right, and never could...I never had a PTC, but mine is a BDR converter. He's out of Buffalo, NY. Worked great out of the box for the 383 I had, and the few times I had some full throttle romps just fooling around with this 402 before I shut it down I still love it. I did what @Jody Treadway said back then...called the guy (whomever you choose), answered his questions, gave him the magic 16 digits, a date, and 3 more digits after that, and a week or so later had myself a torque converter that I think I'll still be happy with running behind this engine. ....if I ever get it moving again...

Hell, if it wasn't for the lack of time to pull it and the ride both ways, I'd send mine down on the brown truck just so you could give it a shot and see what you think.
 
Thanks for all the help. I called PTC and ordered a new converter. Nice folks I just hope it works.
 
Update. Ordered on Wednesday. On my front porch Saturday. Teachers took off Wednesday and I took off Thursday and replaced converter. Finished up today. It is perfect not too loose, not too tight , just right. Thanks for the excellent advice!
 
moldman05 said:
Update. Ordered on Wednesday. On my front porch Saturday. Teachers took off Wednesday and I took off Thursday and replaced converter. Finished up today. It is perfect not too loose, not too tight , just right. Thanks for the excellent advice!
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Do they do women?


For that description I had to ask.
 
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WARRIORWELDING said:
Do they do women?


For that description I had to ask.
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For anyone that comes across this thread,

A huge thanks for all those that said to call ptc.

For all the headache and guessing as to which coverter to run, the time spend taking trans in and out,

As stated above.....

Just call ptc, spend $500 and get a converter built. It’s worth every penny.

Works perfect, couldn’t have asked for a better working converter.

For the time/money spent. It’s one of the easiest things to get right.
 
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