Dyno in 2WD mode

No Spin

New member
I have read about some of our members using the 2WD test mode to run their cars on the more common 2WD dynos.

(I also read in the BGB that driving in this mode was not recommended. My thinking was that actually driving in this modes would be like towing it with wheels down - AND not the same as sitting on a dyno with the wheels spinning).

Q: Is there any chance of doing any harm to the powertrain while running in 2WD mode on the dyno?
 

jprine01

New member
Well its not exactly the same as towing it with the wheels down, as that would be working the center diff like crazy. In FWD mode it sort of disables the center diff. For dyno purposes (not driving around) I think its safe. I've heard of one guy that selected FWD mode without putting the bolt back in to secure it, on the dyno it moved and destroyed the trans. But that is because the lever moved while he was putting power down not because it was in FWD mode. Not sure how accurate dyno readings are going to be in FWD mode though.
 

2of81

New member
jprine01":1oa4kjbr said:
Not sure how accurate dyno readings are going to be in FWD mode though.

Accurate enough to tune an EMS on. Bragging numbers, yea I wouldn't use this.
 

Conan

New member
jprine01":1pfemxnq said:
Not sure how accurate dyno readings are going to be in FWD mode though.
Accurate for flywheel HP, however it will give you more HP at the wheels due to less power loss in FWD mode. And yes, you can tune in that mode.
 

MATT-S

New member
The previous owner of my black 185 drove it for over 2 years in 2wd mode before the tranny gave up. It was that way when he bought it. So it can't do a massive ammount of damage using 2wd mode, but obviously it's not designed for it to be run that way.

Cheers

Matt
 

SuperWhite92

New member
The 165 manual refers to it as emissions dyno mode, too, so it was obviously intended to be run on a dyno where rolling AWD emissions dynoes aren't.
 

GT4_CR

New member
Sorry to ask this but ive never seen the lever that connects and disconnects 2wd and awd. Can someone place a picture of this part, or explain like if i was 10, where is it located so that I can know this better. :oops:
 

GT4_CR

New member
Gary":wn5hhogl said:
http://home.covad.net/~billprice/Cars/index.html
Click on the "The infamous FWD jpegs!" link


Thanks a lot for the info. Ive seen that lever but never touched it. In my country we have a obligatory emission and condition check for cars, and Im worried for what can happen if i dont disconnect the transmission...
 

richard

New member
A month ago I tuned my car on a 2wd dyno. Everything went well until my tuner told me my car was ready but he wanted to give it a spin to check everything out. He went alone (I should have gone with him), 5 mins later called to ask for a tow truck! later we found out a part called diferential lock sleeve had broken. This part is not available in the US so it is a special order from Japan. Being A1 the most sold part in Toyota´s registry, this part is f5...this means only God knows when I will receive this part...
so after saving for months , waiting for performance parts, and tune , I didnt get the chance to try drive my freshly tuned all-trac!!!... this was like receiving a christmas gift without batteries..

So I dont know if the damage was done during dyno time or while driving in 2wd mode.
 

TheRealDealGT4

New member
I dynoed my car in fwd mode, using my aem, it works and doesnt really damage the trans if you dont use it for a long time, but it did mess with my maps when i connected the 4wd again due to the added load in the rear. your best bet is to find a 4wd dyno and do it right the first time or do it again, like i sadly have to do :cry:
 

gearhead313

New member
Man, i'd really like to know what is going on in that tranny that you can't run it long in FWD. in my 165 bgb, it says to only run it in 3rd - 5th.. so does that mean that there is too much torque being applyed to the tranny in 1st and 2nd? It just doesn't make sense to me...
 

pepper

New member
gearhead313":2guddp39 said:
in my 165 bgb, it says to only run it in 3rd - 5th.. so does that mean that there is too much torque being applyed to the tranny in 1st and 2nd?

Yeah, that's what I think it is. The front diff is only designed to handle half the torque put out by the motor in normal use. Just not a beefy enough part to handle the full power on an extended basis, although some have obviously done this for awhile.
 

gearhead313

New member
So, do you agree that it would be alright to put it in 2wd, tow it to the dyno, strap it on and ease it up to speed in 1st, 2nd and 3rd then only make a pull in 4th. I'm really thinking about doing it this way and hopefully nothing goes boom!!
 

nfn15037

New member
Why not just go to an AWD dyno? Seems like a lot riding on your hypothesis, with very little real information known about the subject.
 

nfn15037

New member
Bleh, stupid dyno shops.

To me, it seems the reason the BGB says only to use the higher gears is because the torque miltiplication in 1st and 2nd gear generates thousands of ft/lbs more torque. As someone stated earlier, the front diff is only designed to handle 50% of the torque, with the rear diff handling the remainder. It should be fine on a chassis dyno, just do some steady state to dial in everything but WOT then do some swept runs in 4th. It shouldn't take too many pulls to get WOT dialed in properly, which sould save wear on the diff and front driveshafts.
 

coyoteboy

New member
From what i see in the Toyote manuals you shouldnt use the 2wd mode above certain speeds and presumably not above set torques. Its there to let you run basic tests at low speeds, not for power transmission. You might not kill your viscous unit immediately but you will damage the fluids in it by overheating them which will all add up to reduce the lifespan of the parts.

I have been tempted to do this a few times but then realised the lower cost of 2wd dynos is not worth the extra expense if the transmission fails and i have to pull the box out.
 

alltracman78

Active member
It's not too much power for the front diff.
With the way our drivetrains are overbuilt do you seriously think it[front diff] couldn't handle 200 hp/ft/lbs torque?
Or even quite a bit more?

"Shifting" that lever is just like when you shift the trans.
It slides a sleeve in the T case, locking and/or unlocking.
I forget exactly what shafts are actuated. It's been a while since I tore one apart.
 
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