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First gear ONLY burnout with a TH400..

36K views 42 replies 23 participants last post by  94-6spd 
#1 ·
After seeing the sucess that some guys have with a very short burnout.. Plus MT's recommendation for only a short burnout with their slicks.. I'd like to try first gear only burnouts with my T400..

Are there any problems with burning out the water and letting the tires chirp when they start to hook, in first gear??

Since I only run 3.55 gears with 28 inch tall tires.. I don't think it would be easy to start a burnout in third gear.. And I don't think I need the 1-2-3 in the water style burnout either..
 
#7 ·
High gear only burns!!!! BTW have you ever got a handle on the thing yet... Im not going to be around up here for long. Let me know if you need help at the track or whatever
I just put fire to it for the first time this past weekend.. And my brand new BG King Sumo fuel pump leaked like a cive.. It will probably be on jack stands for another couple of weeks, till that is resolved..

I don't want high gear only burns.. I want to know if I'll hurt the tranny with first gear only burns.. Kind of like the burnouts that Lynch does on his 10.5 tire car.. Short and less intense..
 
#4 ·
I doub't you'll get enough wheel speed out of the 1st gear burnout to build the tire heat.

I skip 1st gear starting in second and shift to high quickly and keep it short. Some will do a second gear only. It's been said to NOT shift 1-2 in the burnout box to protect the intermediate sprag.
 
#29 ·
I always do a 1 and 2nd gear burn out and never had an issue yet on my 400th. But i have a spragless convertor and valve body. I also leave on the trans brake in 2nd gear to.

Interesting. I have been looking for a spragless valvebody especially with the second gear transbrake option. Where can I get one?
 
#13 ·
On some converters with a stock type spag yes you can hurt the sprag on the converter if the wheels hook or shake in the burnout... As for the th400 you should stay with a high gear only burn out not to save the converter but the trans.... I only give opinions based on experts teaching me what goes wrong and why so take it or leave it Im not here to fight anymore....lol
 
#14 ·
I'm not looking for a fight.. I just want some advice from someone who knows ;) ..

I noticed at the World Street Challenge, that Tim Lynch did very short burnouts with his 10.5 car.. I figured that with a first gear only burnout, that the thread would stay flat and heat the tire evenly all the way across.. Instead of spinning up on the crown of the tire, from the high wheel speed of a high gear burnout..

I had always previously did my burnouts starting in 1st then going to 2nd.. I never hurt the tranny like that.. I could feel when the tires were about to start hooking, and I'd roll out the gas just before they barked..

I now know that I wasn't doing my trannies sprag any good.. And I was just wondering, what in a th400 can be hurt by staying in first gear.. And rolling out the throttle when the tires start to hook..
 
#15 ·
Hey if you wanna stay in first and get no wheel speed then it wont hurt it at all... But traction will suffer if the tire doesnt get the proper temp... BTW Tim does high gear burn outs and he has a P/G in his car.... The reason for this is close to what you are talking about but his 10.5 W tire reacts a bit different than a true 10.5 tire...

But you might wanna ask someone that knows something cuz I ride the short bus everyday obviously........
 
#17 ·
Question :
F.Rizzo, can you go into more detail on why first gear burnouts are a bad thing with a 400? Can you give a play-by-play of how a rev. manual TH400 works in 1st, then what it does in 2nd, and then high? Which drums are doing what? When is the band applied and released? I used to have a C4 with a brake and I've been told the 400 operates differently. Thanks.

Answer :
THM 400 rev. manual w/t-brake clutch & band application

Reverse - Direct clutch & Rear band

1st gear - Forward clutch is applied & the Low roller clutch is holding (needs to see load)

1st gear w/brake on - Forward clutch, Direct clutch, Low roller clutch holding & Rear band applied.

2nd gear - Forward clutch is applied, Intermediate clutch is applied & Intermediate sprag is holding

3rd gear - Forward clutch is applied, Intermediate clutch is applied, Direct clutch is applied & Intermediate sprag is overrunning.

THM 400 Geartrain

1st gear under acceleration - Front planetary/reaction carrier is being held stationary from the low roller clutch locking against the center support, the rear planetary/carrier is rotating with the driveshaft, the direct drum is being antirotating via the sun tube @ a speed determined by which gear set is in the trans (2.48/1st is 84% of input shaft speed). The combination of both the front & rear planetaries gives you first gear.

2nd gear under acceleration - The intermediate clutch is applied & along with the Intermediate sprag holding this stops the dirct drum from antirotating & also releases the low roller clutch which intern eliminates the front planetary/reaction carrier. Now the only active planetary is the rear one thus giving you second gear.

3rd gear under acceleration - The Intermediate clutch stays applied & the direct clutch is also applied which allows the Intermediate sprag to freewheel thus eliminating the rear planetary & giving you 3rd gear.



The low roller clutch is designed to work under load & for this reason it is highly recomended that you do not do burn outs or hard peddle the car while in first gear. The loading & unloading of the low roller clutch causes the rollers to slam against the springs & flatten them. If the low roller fails under load it will send the dirct drum to 3.25 + times engine speed, usally very bad when there is a cast drum involved. Another big issue is the Intermediate sprag also works under load, it needs moments of time to load the sprag elements properly & also the sprag race dementions come into play. Now we are only talking about mili-second, but this is accomplished by bringing the motor down to drivshaft speed during the gear change, where as in the burrnout you are bringing the driveshaft up to enging speed during the gaer change which can & will "shock load" the Intermediate sprag.

Remember when in 1st gear you are antirotating the direct drum then stopping it to get second which in a burnout situation this unloads the low roller rapidly & has to lock the intermediate sprag with out the proper "time" to load. This will cause unnessassary wear & abuse to the sprag, then resulting in premature sprag failure

Hope this helps
 
#19 ·
This is where alot of major damage gets done to tranys.

I have disassembled tranys in front of customers & told them exactly how they do their burnouts just by the condition of the unit.

Incorrect burnouts are the worst offenders of trany failures without a doubt !
 
#20 ·
Thanks Rizzo... I'm going to copy and paste your th400 gear changing info on my computer.. So that I can read it over and over until I understand it well..

Err ahh... I guess I learn to do my burnouts STARTING in 3rd gear..

The video link below is the way I've always done my burnouts... Luckily, without a problem..

http://media.putfile.com/blowoff
 
#28 ·
Hutch said:
It goes for everything, if you can start in high do it.
Hutch
Doesn't the C4 have a different method of going from 1-2 which makes the 1-2 burnout safe?
 
#35 ·
Huh X2.............. How do you get a transbrake to work in ANY gear besides 1st or reverse?

I use mine to engage reverse.

When I had a TH400 I did a 2nd and 3rd gear burnout for awhile. I later learned to roll through the water, put it in 3rd, and smack the throttle hard and quick, get the rpm's up to 6000, then let off a little bit, the tires would heat-up, burn the water off, and then start to pull the motor down. I would give it a little more throttle, look in both mirrors for smoke, then release the line lock and get off the throttle easily as the car moved forwards. Sounds like a lot going-on but it only takes 5 seconds!

Now I have a 'Glide and do the same exact method. I never chirp my tires! To me, when you hear people "chirping" their tires, that can't be good for anything in your drivetrain.

I've made thousands of passes and have never had a trans issue. (Except for the convertor bolts that sheared-off one night when I lifted in the traps!)
 
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