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80:1 crawl with manual transmission…Thoughts?

ssray

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Apr 19, 2010
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Just wondering what experience you’ve had at a crawl ratio around this. Wheel speed would be just under 1mph at idle. Either of the two engines I have would be over 200 ft/lbs at 1000 rpm so good low end torque.

Just looking for opinions on rock crawling. I would like to be able to get to cool places, just not looking to beat the Bronco up just to say I’ve been up such and such trail if you get my drift. I’d have something else if I did that.

Scott
 

okie4570

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With a np435 in 1 low, T shift Dana 20 in low, and 4.11 gears I'm 68:1. A jump to 4:88 gears would get me to 79:1. I've never really felt lacking with what I've got, although if I'm pointed nearly straight up, I can't idle up the obstacle but requires very little pedal, and I've gone over and through lots of places I probably wasn't supposed to with a good spotter and locked front and back of course. Any time I drive my 71' I've got 15 miles of highway to drive before I get to town, so I've been hesitant to go with lower gears. I only make it out to crawl one or two times a year right now, too many irons in the fire. What setup do you have or thinking about? The "die hard" rock guys are way low gears, low transfer case gears, even doublers along with EFI and they can idle through nearly everything.

6.68 x 2.42 x 4.11 is 68:1
 

Yeller

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Scott, 80:1 will comfortably get you through 95% of the trails that your not risking body or mechanical damage in the country.

Edit: as Okie said I believe you’ll be quite happy. When I ran a manual I was happy at 60:1
 

Yeller

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In addition I know you’ve seen me say it before, I truly believe everyone gets to wrapped up on crawl ratios. My current auto shifted trucks are at 42:1 and 30:1. The 42:1 is my bronco and would not want it deeper, to me it’s perfect.

When I ran a manual if it was idling and stalled I’d start it in gear with the clutch out, with a modern high torque starter, use it to your advantage, no need to stress and try to 3 pedal it.
 

ET

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I had np435/3.15teralow d20 /4.56 gears. I never had problems idling through except one tough trail at K1 and my spotter told me to slow down. At 80:1, you should be able to run trails you want.

Eugene
 

admin

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With a np435 in 1 low, T shift Dana 20 in low, and 4.11 gears I'm 68:1
I've run this exact setup with 33" tires for several years. It's served me very well rock crawling in AZ and Moab. No complaints about going too fast over the obstacles.
 

ngsd

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I run a NP435, D20 with Klune V, 4.56 37" tires and about 168:1
 
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ssray

ssray

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Thanks for all the great comments….My 04 Rubi is in the 60’s but I’ve not had it in much for rocks around here. lol I have a NV4500 in a 94 GMC so am familiar with those but they are hard to find along with parts as well. A Tr 4050 with an appropriate atlas and gears would get me to that ratio. Something thats intrigued me is the T56 magnum. Actually a bit less than a 4050 but 4wd conversions are not common and would need a case ratio like 5.44 of an Atlas 4 sped or a good old 205 with a magnum underdrive or such. Long conversion as well physically. Really adds up cost wise and I haven’t seen a 205 through the local junkyards. So many options out there, I think that’s why this has gotten put last. ;)
 

79INA69

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Apr 30, 2018
Messages
159
In addition I know you’ve seen me say it before, I truly believe everyone gets to wrapped up on crawl ratios. My current auto shifted trucks are at 42:1 and 30:1. The 42:1 is my bronco and would not want it deeper, to me it’s perfect.

When I ran a manual if it was idling and stalled I’d start it in gear with the clutch out, with a modern high torque starter, use it to your advantage, no need to stress and try to 3 pedal it.
When you factor in the torque converter it usually add the affect of 2x added to the first gear in the automatic transmission right? C4 and C6 only have a 1.46 or 1.6 to 1 first gear correct?
 

Yeller

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When you factor in the torque converter it usually add the affect of 2x added to the first gear in the automatic transmission right? C4 and C6 only have a 1.46 or 1.6 to 1 first gear correct?
True to a point, the real factor is closer to 1.6-1.7 but regardless the fluid coupling makes it variable and sudden shock from a ledge or bounce doesn’t kill the motor or brake as many parts.

A little taller 65-80:1 with a manual and 37-50:1 with an auto create several things. One is a small bit of wheel speed when needed, a small amount of momentum makes throttle control easier and more effective. Too deep of gearing limits the effect on throttle input reducing the ability to speed up when needed. In my opinion once you exceed 50:1 with an auto and 80:1 with a manual the beneficial returns diminish rapidly and become more of a liability than an advantage. The only time they are an advantage is rare, and usually those can be overcome with driving technique and in reality very few people ever get in those situations to begin with, you really have to be looking for them.
 

Broncobowsher

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34,835
When you factor in the torque converter it usually add the affect of 2x added to the first gear in the automatic transmission right? C4 and C6 only have a 1.46 or 1.6 to 1 first gear correct?
The actual gear ratio is 2.40 or 2.46 for the C4/C6/AOD stuff.
Using the convertor you can't just automatically multiply b2x and call it good. The multiplication is a huge variable. How much slip (engine speed to input speed), how much torque is applied (how deep are you in the throttle), even output speed. And the more you call for the convertor to make torque, the more heat it makes.
Watch videos of stock rigs with large tires. They will just roll into an obstacle. Small log, rock, parking curb will work just as well. They roll into it, often bouncing back a little. Come to a stop. You hear the engine throttle up, a lot. As the tire climbs the load goes away and the vehicle rockets over the top in an uncontrolled manor. That is lack of gearing and making up for it with "the torque convertor is 2x gearing".
Not that the torque multiplication is bad. On the street it is great. You take off from a stop, have great take away torque and in a well developed powertrain the multiplication phase (from a dead stop) quickly transfers into a coupling phase (minimal slip) and it is almost like a CVT transmission getting from a stop to speed.
Early automatics that didn't have a torque convertor, just a fluid coupling, would have a steep first gear in the 4:1 range. Much lower than the manual transmission. It was needed as the automatic didn't have the ability to rev the engine and use a clutch to get off the line.

As for manual transmission low range gearing. I ran the typical NP435/D20/4.11s on 33s and that got me through some pretty nasty stuff without clutch abuse. Wanting to play with harder stuff was when I went to an automatic, so I could really dial in the super slow speeds. Lots of gear so I didn't need the torque convertor doing multiplication. I could engine brake down steep hills like a stick could. rarely did I need anything above a fast idle.
My daily driver is 43:1 in a manual transmission. I have driven it through some fairly nasty rocks while towing a trailer no less. Stalled a few times. But not abusing the clutch either. That is a locker and I could spin tires with a slight amount of throttle. So enough gearing. Wanting 80:1 would let you get into the idling and slipping tires at the same time (depending on tire size)
 

jamesroney

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Thanks for all the great comments….My 04 Rubi is in the 60’s but I’ve not had it in much for rocks around here. lol I have a NV4500 in a 94 GMC so am familiar with those but they are hard to find along with parts as well. A Tr 4050 with an appropriate atlas and gears would get me to that ratio. Something thats intrigued me is the T56 magnum. Actually a bit less than a 4050 but 4wd conversions are not common and would need a case ratio like 5.44 of an Atlas 4 sped or a good old 205 with a magnum underdrive or such. Long conversion as well physically. Really adds up cost wise and I haven’t seen a 205 through the local junkyards. So many options out there, I think that’s why this has gotten put last. ;)
Why are people having a hard time finding parts for their NV4500? What exactly is the problem? Every single piece of that thing is available in the aftermarket, (and I think I've bought every piece of one thru distribution.)

The rare and unsupported 6.34:1 first gear NV4500 in the 94 Chevy has been a problem for years. But that's a 1 year only oddball. The rare an unsupported 19 spline input NV4500 in the 93 Dodge is also a problem. But everything in later production with a 5.61 first gear is still available. So yeah, if you want to keep your 1994 GM bell housing, then you need the 1 year only small index 95 case with the 5.61 gears...but that's only if you are going to rebuild it. And since Chevrolet never built an engine that can make enough power to hurt an NV4500...there are still plenty at the re-cycler.

Just because Advance Adapters stopped selling complete transmissions, and their distribution network got left in the weeds...doesn't mean that NVG is dead. (OK, New Venture was technically killed by Magna last year, and is MOSTLY dead...but aftermarket parts persist.)

A TR4050 will be the ultimate transmission in unobtainable parts. Tremec is famous for making things that they don't support. Try finding a countershaft cluster for a Tremec 3550, or a shifter for an early TKO.

I don't know what you are trying to accomplish, but your TJ Rubicon is close to perfect in all regards. It's the best Jeep ever made, and better than any Bronco that ever left the dealership. If you want to turn your Bronco into a Rubicon...the answer is the AX15/NV3550, and an Atlas 4.3, and axle gears that match your tire size. (4.10 for 33's, 4.56 for 35's, 4.88 for 37's, 5.13 for 38, and 5.38 for 40's) If you just want to annoy me on the trail by crawling slower than everyone else, then by all means get the Atlas 4 speed, or any of the absurd multi case doublers. My NV4500/ Titan black box / 205 in the Bronco was way too long, and very heavy! But yeah it crawls slow. But it can't back up, and it can't sling mud in reverse. So it's a bad idea.

If I could put any transmission into a Bronco, (...and I can) It would be the NV4500. (Or a ZF-S5-47) and a Dana 20. But no one is out there breaking their Bronco's anymore. So yeah, turn your Bronco into a TJ and bounce curbs at the Kroger.
 
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ssray

ssray

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More interesting discussion!!! Automatics do tend to dominate the off-road scene. Another factor I’d imagine comes in to play is stall speeds but maybe not as much as drag racing? I for whatever reason have always been a manual guy. Just enjoy driving them. Currently working for a neighbor for harvest and driving a truck with a 10 spd Ultra shift and can say I don’t really like it. I’ll take my 10 spd road ranger any day.

James,
To clarify I haven’t had problems trying to get parts for the NV4500. The 94 is still a driver and going strong other than rear lower cab corners falling apart like a lot of them do. I’ve just seen so many mentions of availability issues. Maybe over blown or some not knowing where to look.

Jay Leno is not gonna be happy when he hears about his 4050. LOL 😂

Goal for the Bronco for me is an all around performer. I want to have a fun to drive, reasonably comfortable on road, so I can trip with it without trailering if I like. I believe I could get into overland travel as well. Colorado is next door and offers a variety of travel. And then there’s Moab and the many other areas of Utah a state and a half away from me. The Rubi has taught me that low can be a disadvantage as well. It is not so great for running country roads in deeper snow for example. Maybe 25 mph before rpms get carried away. The Bronco and GMC are about perfect with the 2.5 area range of transfer case for that type of thing. That 6.34 1st gear does really help if you want slow with a normal transfer case. Dad and I used to do irrigation pipe with it and low range. I’d get it rolling and get out and unload or load on the go. I’d have to go bump the steering wheel occasionally but totally workable. :)

What’s a Kroger? Never seen one. ;) ;) ;)
 

Broncobowsher

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Jun 4, 2002
Messages
34,835
Friend has a Rubicon, also found the 4:1 transfer case was too low. Ended up putting in a Rubi crawler. Not because he wanted the doubler, but because he wanted a regular low range for the stuff between highway and crawling.

Many years ago I was on a trail with someone who had the 4.86 gears for the Dana 20 and a C4. Great on the highway, great in the big rocks. The sand wash between the two, it sucked. In low range he had no tire speed. In high range it would boil the transmission fluid.
 

JWMcCrary

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Both of my Broncos have cold duck doublers with C4, I would hate to have to go back, it sure makes easing over and around tight tough spots a lot easier.

2.46(C4) X 2.46(CD) X 3.15(D20) X 4.30 = 82:1 73 with 393 37 inch tires
2,46(C4) X 2.46(CD) X 2.46(D20) X 4.88 = 72:1 75 with 302 38 inch tires

At a glance it looks I should have these the other way but in high range they are matched very well for driving on the street, everything in low you really can't tell the difference.
 

snipes243

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I have been running an NV4500 with a 4.3 atlas and 4.88 for years great little combo. Works great in the rocks and the flys down the highway. Only odd thing is I don't use first gear on the street unless I'm crawling through traffic All starts are in second gear. Generally on the trail I run first gear with High range. Then second/third gear when in low range.
 

Broncobowsher

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Jun 4, 2002
Messages
34,835
I have been running an NV4500 with a 4.3 atlas and 4.88 for years great little combo. Works great in the rocks and the flys down the highway. Only odd thing is I don't use first gear on the street unless I'm crawling through traffic All starts are in second gear. Generally on the trail I run first gear with High range. Then second/third gear when in low range.
That reminds me of driving the NP435. That granny gear was actually very useful in stupid heavy traffic and parking lots.
 

79INA69

Jr. Member
Joined
Apr 30, 2018
Messages
159
The actual gear ratio is 2.40 or 2.46 for the C4/C6/AOD stuff.
Using the convertor you can't just automatically multiply b2x and call it good. The multiplication is a huge variable. How much slip (engine speed to input speed), how much torque is applied (how deep are you in the throttle), even output speed. And the more you call for the convertor to make torque, the more heat it makes.
Watch videos of stock rigs with large tires. They will just roll into an obstacle. Small log, rock, parking curb will work just as well. They roll into it, often bouncing back a little. Come to a stop. You hear the engine throttle up, a lot. As the tire climbs the load goes away and the vehicle rockets over the top in an uncontrolled manor. That is lack of gearing and making up for it with "the torque convertor is 2x gearing".
Not that the torque multiplication is bad. On the street it is great. You take off from a stop, have great take away torque and in a well developed powertrain the multiplication phase (from a dead stop) quickly transfers into a coupling phase (minimal slip) and it is almost like a CVT transmission getting from a stop to speed.
Early automatics that didn't have a torque convertor, just a fluid coupling, would have a steep first gear in the 4:1 range. Much lower than the manual transmission. It was needed as the automatic didn't have the ability to rev the engine and use a clutch to get off the line.

As for manual transmission low range gearing. I ran the typical NP435/D20/4.11s on 33s and that got me through some pretty nasty stuff without clutch abuse. Wanting to play with harder stuff was when I went to an automatic, so I could really dial in the super slow speeds. Lots of gear so I didn't need the torque convertor doing multiplication. I could engine brake down steep hills like a stick could. rarely did I need anything above a fast idle.
My daily driver is 43:1 in a manual transmission. I have driven it through some fairly nasty rocks while towing a trailer no less. Stalled a few times. But not abusing the clutch either. That is a locker and I could spin tires with a slight amount of throttle. So enough gearing. Wanting 80:1 would let you get into the idling and slipping tires at the same time (depending on tire size)
My combo yields 44:1 in double low. C6 203/205 with 4:56 gears. It would be 125:1 in first gear with an NP435 (sitting in the garage) I feel like the how low can you go phase is long gone. Automatics are very common and preferred now by most. Doublers in general seem to be only rock crawlers in Ca and dry desert states. As stated if there is a lack of traction or momentum is necessary then 200:1 is not going to crawl up the hill. The NP435 has such a low first gear that you can either use it and have much taller gears for the freeway or as some do, just wheel in second gear. With better and better suspension and tires, it is no longer such a harsh ride to go over stuff quicker. The control factor of ultra low gears was great for crutching the harsh ride of ranch shocks at speed. I would prefer the NV4500, and would not swap it out either.
 
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ssray

ssray

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Really a wealth of info that has been put forth here. Many thanks again to every one. Interesting how low some are using. I sure won‘t be worried if I don’t come up with something as high as mentioned.

Scott
 

nvrstuk

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Interesting how personal bias (not facts) gets mentioned by a few. If I was going to use bias, not facts I'd say the 4500 that James is talking about is a PIG of a transmission- same with the ZF, but I won't. I will say they have their place but it's not when you want momentum and keep your tire speed up- fact, not bias.

If you never need momentum then any wide ratio trans (those with huge gear splits) will work pretty good.

Another personal bias "... But no one is out there breaking their Bronco's anymore. So yeah, turn your Bronco into a TJ and bounce curbs at the Kroger." Curious- Why even say this?

I have run 9 different transmission/transfer case/doubler options in the same Bronco over the last 6 decades ('70's - 2022). I've done the stock stuff, toploader 4 spd combo's, 3 spd OD's, ZF's with doublers & D20, ZF with doublers w/Atlas (loved this combo but not anymore), C4's, 4r70's with doublers with/without NP205 and 6r80 with Atlas. Steve convinced me years ago that extremely low gearing can be hazardous- and I've never looked back! (thanks!)

Doesn't matter what works for me- this is about YOU and your wheeling/driving style.

If you crawl in the rocks you need something different than a mall crawler would. If you play in the sand or deep snow you do not want a transmission with huge splits because you almost come to a stop even shifting as fast as you can (which isn't fast).

I drive almost everyday comforrtably (very important adverb) at 70mph and around our country roads and thru our little town. Since I only have one driveable Bronco and I use it for everything.

I think I have found (for me) the best trans and gearing combo for what I do. Deep snow, sand dunes (not packed beach sand), highway, DD (like 175mi/week daily), light trails and rock crawling like Sand Hollow/Moab. This is my opinion after decades of experimenting with 200+:1 crawl ratios and other gearing options. Not saying this is for your driving style.


Many benefits but I haven't experienced a drawback yet with the 6r80, 3:1 Atlas combo.- caveat is - the rest of the Bronco is built around it. Engine size, 40"s, 5.13"s all compliment each other without any drawbacks but this is for my style of wheeling/driving-not necessarily yours. With that in mind a big truck transmission that James likes might be perfect for your intended uses but holy cow- saying one trans with the smallest weakest transfer case coupled to it & available for a Bronco is the best is a bit out there... wow.

I'd never run a D20 again in anything but a street rig that only sees light at best, off road duty. They were built for 28" tires, 170 HP, 3.5:1 gears and a 3 spd. No torque there compared to what most of us run today. Torque kills parts.

Apologize for this being book length but the correct trans/t-case/engine/ tire size/ axle gear choice makes or breaks (literally) your rig and will ruin your vacation when the weak D20 breaks when on that once in a lifetrime trip to Moab or wherever. It happens often and I see it every year at Moab. Trips over when the D20 explodes.

Best of luck in you choices- it's taken me 46 years. :)
 
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