Running in 4WD hi at high speed with the Dana20

[landshark99]

Just throwing this out there for those that have ran their Broncos with a Dana 20 at higher speeds in dirt/sand (not rock crawling or the like) over extended periods of time. What are the weak links besides the output shaft? Will the Dana 20 survive running 200-300 miles at 30-50mph with a few higher speed runs around 60-90 mph for 20-40 miles at a time? Other things to be concerned with?

 

[SHX669]

I wouldn't run in 4WD at speeds over about 45mph . I've driven 100 miles or so in 4wd at reasonable speeds.

 

[sykanr0ng]

High quality synthetic oil.
A heavy bottom cover to help stiffen the case housing, such as 3/8 inch steel plate.

 

[bknbronco]

i got a 68, 289, 3 speed manual, dana 20, 5:38 gears. I dont have a rear drive shaft yet so i been running around in front wheel drive. So basically 4HI with no rear drive shaft. I run in down the freeway at 60is. With my 5:38 gears i cant do much over that anyhow.

 

[Broncobowsher]

Should handle it just fine.

There have been a lot of people who accidently left the transfer case in 4WD and drove hundreds of miles, at highway speeds, and never knew they did it.

 

[sanndmann3]

I've broke 3 20s running around in the sand. Never broke a rear output, probably due sand and not hooking up. All my failures were related to the teeth on the low range rears. Only run low range out in the sand to keep trans temps manageable. The high range helical gears are much stronger than the low range spur gears so you would probably be better off than me...

 

[68ford]

Not long periods like hours on end, but hard runs in 4 hi all the time t-case never seems to care

https://www.instagram.com/p/BrbMQqlgTOl/?utm_source=ig_share_sheet&igshid=1d2i7iqdc81sl
https://www.instagram.com/p/Bf4gZDflx1k/?utm_source=ig_share_sheet&igshid=1wlgzg5d6tqk

 

[okie4570]

Should handle it just fine.

There have been a lot of people who accidently left the transfer case in 4WD and drove hundreds of miles, at highway speeds, and never knew they did it.

Yep, one 71' bronco with twin sticks, one wife who wanted to drive it that week, and about 250 miles most of which were on the highway lol. That was in 2012, no issues.

 

[landshark99]

Thanks, that’s what I figured but just wanted for check in on other experiences!

 

[Broncobowsher]

I've broke 3 20s running around in the sand. Never broke a rear output, probably due sand and not hooking up. All my failures were related to the teeth on the low range rears. Only run low range out in the sand to keep trans temps manageable. The high range helical gears are much stronger than the low range spur gears so you would probably be better off than me...

Sounds like your failures were with low range. No problems with high range? I guess not if you are always in low.

 

[71broncman]

Maybe give Duff's a call and as the MAN for some input from the days when he was racing.
Mark.

 

[Broncobowsher]

I bet a lot of those old baja racers ran the entire race in 4WD.

 

[Rustytruck]

The only parts I would worry about long term high speed running in high range would be the inner front spindle needle bearings.

They dont normally have allot of grease available to them unless you pack the whole spindle with grease inside. But these axles were designed long before free wheeling hubs came out.

 

[Broncobowsher]

Spindle bearing loads shouldn't be any different. Lots of NP203 trucks ran the D44 with drive slugs. The bearings only support the stub shaft, they have no idea if the shaft has any torque going through it or not.

But you probably don't want to try the nylon bushings. Use real bearings.

 

[sanndmann3]

Sounds like your failures were with low range. No problems with high range? I guess not if you are always in low.

No problems with high range, only low. Last failure I lost a tooth on the spur gear. another 2-3 minutes of running and the tooth found its way in between meshed gears and made boom sound. corncobbed the slider gear and fractured the case...

 

[landshark99]

Spindle bearing loads shouldn't be any different. Lots of NP203 trucks ran the D44 with drive slugs. The bearings only support the stub shaft, they have no idea if the shaft has any torque going through it or not.

But you probably don't want to try the nylon bushings. Use real bearings.

All new bearings

 

[68ford]

I bet a lot of those old baja racers ran the entire race in 4WD.

Don Moss bronco runs slugs in the front hubs. Not sure in actual 4wd but regardless everything is turning. He is by far most winning short wheelbase 4x4