Possible to temporarily disconnect AWD for RWD dyno?

[fastcougar]

I am getting a 97 V8 AWD XLT this Friday and have the opportunity to dyno the truck in 2 weeks. However, the dyno is not an AWD dyno. My understanding of the AWD system on the Explorer is that it is a mechanical linkage that supplies power to both the front and rear differentials at all times. Is this true? If so, is there anyway to temporarily disconnect the AWD transfer case to the front axle to run in RWD mode? What all is involved if it is possible and about how long would this take to do on a lift?

 

[ccanuk]

I believe there is a third diff in an AWD transfer case that allows power to go either front or back so in theory as long as it's securly chained you should be alright... but their may be a locker installed in the diff in which case you're boned...

I'd suggest removing the driveshaft to the front but then that would be the path or least resistance and no power will got to the ground...

I don't know I think you are pretty much boned.

 

[section525]

You can remove the front driveshaft making the truck 2wd. However, a few things will happen. One being you'll need to use your parking brake while the shaft is out. It is what keeps the truck from rolling while in PARK. Also, I don't think your dyno numbers will be close to accurate. You're still losing power to the front of the tranfercase (5-10% I think). So if you're doing this to get base HP/TQ numbers prior to mods, you may be okay. But they'll probably be low numbers if you're looking for actual power stats. Let us know what you come up with though!

 

[ccanuk]

removing the front drive shaft will allow the U joint half to the front to spin and thus be the path of least resistance and no power will go to the back wheels. the E brake is only on the rear wheels too.

if you put the e brake on while the front wheels are on the dyno rollers, that might work...

I think

 

[IAmTodd]

removing the front drive shaft will allow the U joint half to the front to spin and thus be the path of least resistance and no power will go to the back wheels. the E brake is only on the rear wheels too.

if you put the e brake on while the front wheels are on the dyno rollers, that might work...

I think

I don't think. Path of least resistance doesn't work here. The T/C is mechanical. As long as the front output spins, I would think it senses it moving. But there will still be power loss going to the front which won't show up on the dyno.

 

[V8BoatBuilder]

In the BW 4404 AWD t-case we have in our V8s, there is one solid shaft between the t-case input and the rear output. A gear is fitted over the shaft, driving a chain which turns the viscous coupler and then the front shaft. The t-case oil pump is on the main shaft. Unlike electronic AWD systems, ours is very old-skool. Power is always sent to the rear, and sent to the front if there is slip while the rear axle is turning. When the front turns slower then the rear, the fluid in the VC thickens up and power is transfered. However, since it's fluid, desired slip due to turning the truck at speed is compensated. Its a fluid based limited slip, a cross between a tourque conveter and a limited slip differential.

You can disconnect the front driveshaft no problems - its the best, and only way to run the truck on a 2wd dyno.

You won't loose as much powers as you'd think, due to the direct link. However, there will be drag from the t-case internals. The front "cup" on the t-case will be spinning, btw.

 

[fastcougar]

In the BW 4404 AWD t-case we have in our V8s, there is one solid shaft between the t-case input and the rear output. A gear is fitted over the shaft, driving a chain which turns the viscous coupler and then the front shaft. The t-case oil pump is on the main shaft. Unlike electronic AWD systems, ours is very old-skool. Power is always sent to the rear, and sent to the front if there is slip while the rear axle is turning. When the front turns slower then the rear, the fluid in the VC thickens up and power is transfered. However, since it's fluid, desired slip due to turning the truck at speed is compensated. Its a fluid based limited slip, a cross between a tourque conveter and a limited slip differential.

You can disconnect the front driveshaft no problems - its the best, and only way to run the truck on a 2wd dyno.

You won't loose as much powers as you'd think, due to the direct link. However, there will be drag from the t-case internals. The front "cup" on the t-case will be spinning, btw.

Thanks for the definitive answer! However, I think that I am going to get the dyno done on an AWD dyno nearby at a shop that specializes in Audi's. Thanks for the input guys!

 

[rydinhigh]

you arent going to lose a lot of power from 2wd-awd. we actually dyno'd an awd dsm, then took off the front drive shaft and dyno'd again. The dyno showed a 6whp difference between the two.

 

[section525]

Well.. just for fun I went out and took my driveshaft off. Seems a little peppier. Turning is way easier. I want to take it to the track and throw some smaller tires on it and see what it'll do now!!

 

[fastcougar]

Well.. just for fun I went out and took my driveshaft off. Seems a little peppier. Turning is way easier. I want to take it to the track and throw some smaller tires on it and see what it'll do now!!

It's been awhile since I have been under my Explorer (96 4x4), so please refresh my memory. The layout on the AWD shouldn't be much different except for the transfer case/transmission differences. The Front/Rear diffs should be nearly identical ... I hope I'm not assuming too much. Regardless, the layout of components from front to back SHOULD look something like this:

Front Half Axles > Front Differential > Input Yoke > Coupling (unsure of actual term) > Driveshaft > Coupling > Output Yoke > Transfer Case

Then the Transfer Case Inards (Described in a post above)

Transfer Case > Output Yoke > Coupling > Driveshaft > Coupling > Input Yoke > Rear Differential > Rear Axle

So what you did was simply remove everything between the two front yokes? That would mean that the front diff would spin beause of input from the front half-axles and the input yoke would also spin freely. Same could be said for the transfer case's output yoke that should connect to the driveshaft, which is now not present. Everything should be safe as long as nothing gets caught up in the free spinning yokes ... correct?

 

[Fusion213]

I'm running mine without a front shaft right now(I blew my old one up).
When I put on my 32s, I can light them up!
Now with the 35s, I can peel out for a few feet in them.

 

[ccanuk]

I guess that makes more sense... somewhere I got the impression that there was an oldschool open diff in the AWD transfer case... my bad

 

[boominXplorer]

i notice when I took my front driveshaft out when i first got the truck as there was no differance really felt like seat in the pants wise. Now with the mods I REALLY notice a major loss in low end torque when I remove it.

 

[Mbrooks420]

you arent going to lose a lot of power from 2wd-awd. we actually dyno'd an awd dsm, then took off the front drive shaft and dyno'd again. The dyno showed a 6whp difference between the two.

But that is only drivetrain loss sucked up through the drive shaft, differential, cv shafts and wheels. If you pulled the whole t case off, I bet it would be a lot more than 6hp.

 

[Nitrous SSC]

Great this is the info I needed!

I'm going to regear the rear to 4.10's myself and then have a shop do the 4.10's up front.

 

[V8BoatBuilder]

Great this is the info I needed!

I'm going to regear the rear to 4.10's myself and then have a shop do the 4.10's up front.

Nitrous, I am also thinking of going to 4.10s. I would love to see a writeup and pics of the process.

 

[tmsoko]

Been driving for 39K miles with out the front driveshaft on my Ranger with Explorer V8/ AWD 4404. No issues aside from rolling in park without p-brake and a bit of seepage from the t-case breather. I think the missing front shaft must cause some excessive spinning / oil movement in the case.

 

[V8BoatBuilder]

Been driving for 39K miles with out the front driveshaft on my Ranger with Explorer V8/ AWD 4404. No issues aside from rolling in park without p-brake and a bit of seepage from the t-case breather. I think the missing front shaft must cause some excessive spinning / oil movement in the case.

Todd, a bunch of us V8 guys are trying to find a part-time t-case to swap into our explorers with AWD t-cases. Have you have any more luck since you tried the Expedition 4406?

Please join our research and discussion here: http://www.explorerforum.com/forums/showthread.php?t=97181 as we could use your input.

-Aaron

 

[tmsoko]

Posted on the other post. I have done nothing since long time ago when I popped it in for pictures.

I am now working on a Viper T-56 manual conversion, but the transfer case of choice will still depend on the findings for a 4R70W application. I may just get an Atlas II and be done with it. Found I can get brand new for $1750. Plus, with it's 900Hp rating, will not have to worry about blowing it at the strip.