On the subject of torque convertor multiplication, remember the switch pitch convertors in the Buick GSX? I think that's what its application was for, to create more multiplication for launches.
CK5
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REAL crawl ratio?
- Thread starter 76zimmer
- Start date
Vega's used a switch pitch convertor back in the day.
You have got to be kidding.....I never had the pleasure of a Vega.
Neither have i. I built a V/8 Pinto back in the day when everyone else was building the V/8 Vega. I did use a Ford 302 though.
I have used the Vega convertor though in a hot street car before.
DavidB
1/2 ton status
Great thread. My simple $.02.
The reason an auto doesn't crawl at idle is because, basically, the clutch is in - if it were a manual. Soon as you give it some throttle, it engages. A friend of mine built a Jeep with an AMC I-6 (torquey), a 700R4 with a low stall converter for controlled descents, and 4 to 1 gears in the D300 t-case. I think the axles were 5.13 with 36" tires. Oops! Sure, it crawled great, even at idle, because of the low gearing and low stall converter, BUT...he couldn't stop it going down hill, and barely even uphill! He always had to pop it in N to stop. Highly inconvenient and not very controlled. This is because the converter wasn't disengaging, or "putting the clutch in".
Now, my experiences with gearing...tire size makes a huge difference.
The closer to the engine you make the change, the more difference it makes because it is then multiplied by the other factors.
'81 CJ-7. I-6, T-176 manual tranny with 3 something first, stock D300 gears, 4.10s, 35s. Would do fwy speeds at reasonable RPM, crawled OK, not gracefully or comfortably.
'88 K5. was 700 with 208, 4.56/38s. Went TH400/205/44s...FAIL. Crawled up stuff with lots of throttle, like slipping the clucth, flew off the other side, slammed down. Was OK wheeling in dirt notches. I once got stuck in wet sand cuz I buried it and it literally couldn't turn the tires in R - R is a higher gear than 1.
'95 Ram 2500 with 5.9 Cummins/NV4500/NP241/4.10s/38s. Same as the Jeep.
This one is interesting. '71 Jeep CJ-6 Buick V6 will lug down to 100 RPM, if you haven't driven one with a manual trans, you should try it, it's awesome. 3 something first, 3.46 low, 4.88 gears, 31" tires...55mph top speed = 3000 RPM, STILL too high for crawling. It will chug up stuff, which is so much fun, all my buddies call me putt putt now cuz it sounds like a one lunger....but it falls down the other side of the obstacle unless you load the brakes. A 4 speed with granny 1st should fix it.
Next project = Cheep. Chevy+Jeep, cheap!
TBI 350 SM465 NP241 4.56 one tons 38s. Should work pretty good without expensive doublers, etc. I hate NP208s, broke a lot, but the 241 in my dodge has held up to horrendous abuse. 400+hp/800lb/ft, 7000# truck, and I tow/wheel with it hard.
The reason an auto doesn't crawl at idle is because, basically, the clutch is in - if it were a manual. Soon as you give it some throttle, it engages. A friend of mine built a Jeep with an AMC I-6 (torquey), a 700R4 with a low stall converter for controlled descents, and 4 to 1 gears in the D300 t-case. I think the axles were 5.13 with 36" tires. Oops! Sure, it crawled great, even at idle, because of the low gearing and low stall converter, BUT...he couldn't stop it going down hill, and barely even uphill! He always had to pop it in N to stop. Highly inconvenient and not very controlled. This is because the converter wasn't disengaging, or "putting the clutch in".
Now, my experiences with gearing...tire size makes a huge difference.
The closer to the engine you make the change, the more difference it makes because it is then multiplied by the other factors.
'81 CJ-7. I-6, T-176 manual tranny with 3 something first, stock D300 gears, 4.10s, 35s. Would do fwy speeds at reasonable RPM, crawled OK, not gracefully or comfortably.
'88 K5. was 700 with 208, 4.56/38s. Went TH400/205/44s...FAIL. Crawled up stuff with lots of throttle, like slipping the clucth, flew off the other side, slammed down. Was OK wheeling in dirt notches. I once got stuck in wet sand cuz I buried it and it literally couldn't turn the tires in R - R is a higher gear than 1.
'95 Ram 2500 with 5.9 Cummins/NV4500/NP241/4.10s/38s. Same as the Jeep.
This one is interesting. '71 Jeep CJ-6 Buick V6 will lug down to 100 RPM, if you haven't driven one with a manual trans, you should try it, it's awesome. 3 something first, 3.46 low, 4.88 gears, 31" tires...55mph top speed = 3000 RPM, STILL too high for crawling. It will chug up stuff, which is so much fun, all my buddies call me putt putt now cuz it sounds like a one lunger....but it falls down the other side of the obstacle unless you load the brakes. A 4 speed with granny 1st should fix it.
Next project = Cheep. Chevy+Jeep, cheap!
TBI 350 SM465 NP241 4.56 one tons 38s. Should work pretty good without expensive doublers, etc. I hate NP208s, broke a lot, but the 241 in my dodge has held up to horrendous abuse. 400+hp/800lb/ft, 7000# truck, and I tow/wheel with it hard.
