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View Full Version : How To: Dyno in 2WD Mode



ChrisD
04-23-2010, 05:10 PM
The Alltrac/GT4 transmission can be switched into an "FF" mode for certain purposes. Specifically, the ST165 and ST185 transmissions have this capability. The ST205 transmission DOES NOT.

Although some question the safety and reliability of operating the car in this mode, it is generally very safe. Most failures over the years have originated from people not following the proper instructions, failing to reinstall the set bolt in the mode select lever, etc.

I have personally run my car in 2wd for a 3 hour tuning session, in +30 Celcius heat with zero issues whatsoever.

Also, you get full power readings in this mode. (not 50% as some report) If this were not true, I would have a 470WHP car powered with a ct20b turbo! :hehe: (in actual fact I made 235 on a dyno dynamics)

The following are the BGB instructions for switching to FF mode. It can be done in about 15 minutes after you get to your dyno shop. (do not switch it and then drive there, you do not want the rear wheels spinning while in this mode)

http://bgbonline.celicatech.com/90alltrac/IN/IN-12.jpg

http://bgbonline.celicatech.com/90alltrac/IN/IN-13.jpg

http://bgbonline.celicatech.com/90alltrac/IN/IN-14.jpg

http://bgbonline.celicatech.com/90alltrac/IN/IN-15.jpg

donteatbugs
04-28-2010, 09:14 PM
i should have tried this on my alltrac before i broke the trans.

MidnightBlueGT4
05-11-2010, 07:05 PM
I always wonder about this when i had my st165, but was too afraid to try it.

Speedricer
05-21-2010, 01:30 AM
I will be trying this soon, within the next month.

tubasteve
06-09-2010, 05:00 AM
when you try it , can i rebuild your trans for you? ive seen nothing but bad news when it comes to this. but if you are like me and have 3 trans its worth a shot, but i would never want this cause its not when you normaly drive, also doesnt show for the drive line loss.

maybe im wrong, but there is a reason why it says "never use this mode in normal driving conditions" and to the bost that i know the dynos put a load on the car to simulate the road, unlike with the diagram showing a tech having it on a rack....again, maybe im wrong

ChrisD
06-09-2010, 05:35 AM
"I've seen nothing but bad news on this"

Please provide *actual* evidence of *any* kind. I too have seen a lot of heresay, but never any actual evidence. Have you seen a transmission actually explode when in this mode and properly set up? Ever tried it on your car?

The *only* reports of failures have been a direct result of improper setup. I.E. not setting the bolt to secure the lever in place. I have personally used this mode for over 3 hours of continuous use on a dyno, in +30C to do a full ECU mapping. And yes, it DOES show FULL horsepower. I have seen it on my own car, and have dynographs to prove it.

Also, note that it says FWD for "When using a chassis dynomometer". It asks not to use for normal driving b/c you do not want the rear wheels moving when in this mode.

Sorry if I sound a bit harsh, I don't mean it that way, I just would prefer you provide some actual evidence before saying that everything that I have posted is false. :)

tubasteve
06-10-2010, 05:30 AM
what was faalse? drive line loss, you are NOT spining the rear tires or drive shaft, thus the wt. is no slowing the car, yes maybe 10-15(if that)hp is being lost. the bgb says it, "never this mode during normal driving. look about the bottom of the "in9"

http://www.celicatech.com/imagearchive/bgbonline/88alltrac/IN/IN-9.jpg

im sorry, but it says push if you need rev. and dont use 1&2 gear only 3-5th...my guess...is not to drive it, i belive there is a you tube video actually showing where the transfur. gear fails in three different videos, let me find it.

eh, its not worth the time really, if you feel safe doing this, go right ahead really, its not being done to my car is all. I am showing my veiw, and veiws of many others. no need to shoot down.

ChrisD
06-10-2010, 05:22 PM
I don't mean to shoot you down, sorry dude. I'll try to take the stance of learning and sharing info. I just hate it when people who have never tried it claim that your trans will explode without actually looking at how it was designed. Also like I said, I have done it, and for extended periods of time at that.

With the drivetrain loss, I think I misunderstood. Yes I think you are probably right with FF mode you would probably show a tad more HP, maybe 10-15whp like you say, than on an AWD dyno. That's what you meant right? In any case, I'd say that's not too bad for comparisons sake since it would more easily compare with MR2's. (I had thought you meant that you would see 50% less power, which is definitely not true...otherwise my car has 470whp. My bad. :D )

So, with the comments on page IN-9. Operating on a dyno with the front wheels only spinning is not "normal driving". I think you are referring to points 4 and 5, where the warnings do not apply if you read closely.

4. Refers to viscous free mode. This is for a brake test, disables the viscous coupling however is still in 4WD mode. (Not FF mode)

5. Refers to actual driving situations, not dyno situations. This would be where the rear wheels are moving. Having both front and rears rolling while driving without them physically connected via the diff could certainly cause damage on the road. As for 1st and 2nd gears, I would imagine that the shorter gears multiply the force on the xmission much more than the longer gears, in a much shorter period of time. Again, this is for "normal driving" and NOT dyno time. Clearly, you wouldn't do a WOT run on the dyno in 1st or 2nd. You would usually bring it up to speed slowly and smoothly at lower revs.

Again, note that it says FWD for "When using a chassis dynomometer". It asks not to use for normal driving b/c you do not want the rear wheels, driveshaft, etc. moving when in this mode.

http://www.celicatech.com/imagearchive/bgbonline/90alltrac/IN/IN-15.jpg

tubasteve
06-10-2010, 06:43 PM
all good


good rally though. you point are very true, i shouldnt have been so negitive about the "you will break your trans" so bad on that part.

BUT!

bearing and syncro sets...anyone find them cheaper? looking around $950 complete

lamont
06-30-2010, 12:24 AM
Anyone run this FF mode for any extended period of time? Just wondering if it is a viable FF option for 3SGTE swapped FF cars:thinking::thinking:

Shadowlife25
06-30-2010, 10:48 PM
Anyone run this FF mode for any extended period of time? Just wondering if it is a viable FF option for 3SGTE swapped FF cars:thinking::thinking:

DYNO PURPOSES ONLY.

Please read the thread bud.

If you have swap questions please see the link in my sig and post in the proper locations.

lamont
06-30-2010, 11:47 PM
Will do Shadowlife25.

Thanks:biggthumpup:

Shadowlife25
07-01-2010, 12:10 AM
Just making sure here, because others with low post count have complained:

You CAN see my sig right? If not I would be glad to post links for you :)

Alternately, you can see all the stickies at the top of the Forced Induction section under the swap category.

4agetercel
11-23-2010, 10:39 PM
is it just me or the pics in the first post arent visible anymore

fdfx3
02-14-2011, 12:25 AM
I wouldn't do it, there is a reason why the repair manual from Toyota says: Never use this during normal driving, It will
have a bad effect on the transaxle.

I understand that it's tempting to try and that other done it before, but I would not bet my tranmision on it.

90all-trac
02-14-2011, 01:30 AM
I was under the impression that it was to be used only for towing purposes, because back in the 80's and early 90's they only has those boom, hook and chain type tow trucks

ChrisD
02-14-2011, 03:19 PM
I wouldn't do it, there is a reason why the repair manual from Toyota says: Never use this during normal driving, It will
have a bad effect on the transaxle.

I understand that it's tempting to try and that other done it before, but I would not bet my tranmision on it.

Clearly you haven't read anything that I wrote above. Also, I'm willing to bet you have never actually tried this yourself. However, I will repeat:

Also, note that it says FWD for "When using a chassis dynomometer". It asks not to use for normal driving b/c you do not want the rear wheels moving when in this mode.

fdfx3
02-14-2011, 04:58 PM
Sorry my bad, yes you are right, for some reason I didn't read what you first wrote sorry,
I haven't tried dyno in ff mode, but I once used ff mode for a breaking test on rollers while servicing an st185.

I'm not trying to argue, but just a question dosent it say that you shouldn't exceed speed over 30- 38mph? and if you are doing a dyno pull you will have to exceed speeds way over that dont you?

Grot
02-14-2011, 05:51 PM
Not necessarily, depends on what gear you dyno in

fdfx3
02-14-2011, 06:06 PM
Ok i thought a dyno pull was conducted in 3rd or higher.

ChrisD
02-24-2011, 06:42 PM
Sorry my bad, yes you are right, for some reason I didn't read what you first wrote sorry,
I haven't tried dyno in ff mode, but I once used ff mode for a breaking test on rollers while servicing an st185.

I'm not trying to argue, but just a question dosent it say that you shouldn't exceed speed over 30- 38mph? and if you are doing a dyno pull you will have to exceed speeds way over that dont you?
No prob, just a pet peave of mine that's all. ;)

That is for viscous free mode. FF mode is different. I dyno in 3rd gear so yes you would definitely exceed that speed for WOT runs. :)

cms-gt4
04-25-2011, 08:46 PM
So which mode is best for towing the car on a dolly? I imagine fwd, but I want to verify it.

fdfx3
05-03-2011, 02:02 PM
So which mode is best for towing the car on a dolly? I imagine fwd, but I want to verify it.

Here is a picture ilustrating what to do and what not to do when towing: http://i1101.photobucket.com/albums/g427/fdfx3/Skjermbilde.png

Alin2002
08-28-2012, 08:59 PM
Hello there,
I'm new to this forum, and maybe this is the right thread where I should ask for a solution for the following problem.
I own a 92 celica carlos sainz / rc eu-spec. Last sunday I wanted to take a ride with my car and after a couple of meters driving I heard a odd noise coming from the rear diff. It was a rather a hitting or banging or grinding noise which came repeatedly when driving, but almost at the same frequency, no matter what speed i drove, but only when accelerating. When stepping off the throttle, this noise went away, and another noise like a worn wheel bearing came up. First I thought my driveshaft, or propeller shaft was hitting the exhaust pipe, which is a 3" one, and you know how small the clearence is between all those parts under the car. So i drove to a garage to see what is wrong. On the way there the klonking noise got quieter and finally disapeared, and the other noise made no changes. The mechanic at the garage lifted the car and I was supposed to drive in 4th gear with about 40 KM/H so he could see what or where the noise came from.
And now comes the really interresting part. The noise came up again (klonk klonk klonk) but this time from the transfer gearbox, and only the front wheels where moving. His diagnostic was that the transfer box has to be defective and I should repair it, so I drove to my garage to park the car for a while there until i have the time to repair it. On the way there I noticed that when accelerating more than 3000rpm the speed remained the same and only the revs went up. So I had the idea to make another test: I stoped put the parking brake on 1st gear in and I tried to stall the engine, which it didn't !!!! Very strange isn't it?
Did you encounter this sort of problems yet?

Maybe it is a coincidence, but the day before I had the front end jacked up to change the windscreen washer pump, had the 1st gear engaged so the car wouldn't roll away, but when I removed the wheel well covers i accidentally turned the right front wheel.

I will be very grateful for every idea or solution for these problems. Thank you very much

p.s. what happens if there isn't enough oil for the viscous coupling to engage? could these be the symptoms?

underscore
08-29-2012, 06:09 PM
This is the wrong place to ask such a question, especially since I don't think this has anything to do with 2WD mode. It sounds like your rear diff mount & clutch may be busted up, but I have no way to know without seeing your car.

Also the VC is considered a "non-serviceable item" so it shouldn't be able to run low on fluid unless it is damaged.

Alin2002
08-30-2012, 11:39 AM
Ok thanks,
I've already posted in the Trobleshooting area.