Reaction Times vs Trans Temp - Chevelle Tech
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post #1 of 11 (permalink) Old Apr 6th, 17, 7:13 AM Thread Starter
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Reaction Times vs Trans Temp

Was going to ask this in another forum, but figured not many people in a driveline forum have transbrakes.

I've been having trouble with reaction times. BTE pro brake in a 'glide, new (last year) K&R delay box.

Just to see if there was any correlation between my weird reaction times and trans temp, I put in a trans temp gauge a couple races ago.

Here's what I found. When trans fluid is <150, reaction times are .025-030 slower than when trans fluid is >180. One trans guy has already said 'this isn't possible', but I've got three solid races of data that seem to prove otherwise. Data log shows no difference in converter flash that I can tell or any other signs, car is as deadly consistent as anything out there.
One race was a two race in one day deal- not much time between rounds..Trans temp stayed in the 175-180 range (staging) and around 210 turning on to the return road. Reaction times made sense- had a few .50X bulbs, one .500, a .51x bulb, and one .532 (in the final, I knew I missed it a little but he was .538 and I won, so I'm not fussing about that one)
Next race was the electronics class at the Footbrake 150+50, two day deal with almost 200 footbrake cars, and around 50-60 electronics. Anywhere from an hour-hour and a half between passes. Warmed the car up good before first hit, Trans temp 1st pass was 160 (I was -.002), next pass was almost 2 hours later (and I didn't warm up trans) staged at 130, and added .010 to the box, .034. Next pass, almost the same thing staged around 140 trans temp, .030. Next pass was about an hour and a half later, took .005 out of the box, trans temp again 140, .038 and got loaded up. Next day, about the same thing, except I got lucky and went some rounds..was averaging about an hour and a half between rounds UNTIL 5th round when I had less than 30 minutes since last round, trans temp was 185 when i staged...and I was -.015/dead 9 to his .058/dead 0..(at 8 cars )
Last weekend at Atmore..same thing. Warm car up, stage around 165, -.002 first time shot. Had to fix a head bolt that started seeping a little so I didnt get a second time shot. Run for the money, again, forgot to warm trans up, stage at 135, .050 reaction. First round (about an hour and a half later), same deal, didn't warm trans up, .045, and I'm in the way at the stripe. Bought back and was screwed anyway, dude threw down a .005 package on me, I was dead in the water..
All that said...is something going on with the brake, is fluid temp really screwing with it that much, or what? Right now it's got Hygard in it for fluid, we have a Thursday night TNT/Bracket deal tonight and it's gonna get some Type F put in it if I can find some, to see if it makes any difference.
It could be me, but after doing this off and on 20+ years (plus what the practice tree tells me)...if it were .010-.015 different, I'd believe it could be me. But not .040-050, sorry I aint buying that.
Had a couple trans guys tell me there's no way that fluid temp is causing the 'brake to release slower or faster. Any ideas or opinions??

Greg C.
1969 Chevelle Malibu
New, mildy overcammed 496 "The Dud"
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post #2 of 11 (permalink) Old Apr 6th, 17, 7:50 AM
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Re: Reaction Times vs Trans Temp

I can't say that I have ever seen that happen, but I've also never used the hydraulic fluid in the trans. I use Type F and mine is fairly consistent.
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post #3 of 11 (permalink) Old Apr 6th, 17, 9:13 AM
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Re: Reaction Times vs Trans Temp

stock case or aftermarket case?

What is the reverse feed channel in the rear of the case drilled to?

I could see hot fluid draining out of reverse faster than cold fluid, but not necessarily 30 - 50 defferent in temp and not being worth 40 thou.


I would verify what the reverse channel is drilled to and make sure you run at a consistent temp.

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post #4 of 11 (permalink) Old Apr 6th, 17, 2:42 PM Thread Starter
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Re: Reaction Times vs Trans Temp

Quote:
Originally Posted by Calculated Risk View Post
stock case or aftermarket case?

What is the reverse feed channel in the rear of the case drilled to?

I could see hot fluid draining out of reverse faster than cold fluid, but not necessarily 30 - 50 defferent in temp and not being worth 40 thou.


I would verify what the reverse channel is drilled to and make sure you run at a consistent temp.
The holes are 5/16", the difference is on this BTE brake there are two holes drilled thru the back of the case--which is different from the hipster brakes I've used in the past. The hole from the valve body side is also 5/16" per BTE's instruction sheet..I drilled them myself, as I usually build all my powerglides. Band is adjusted all the way in snug then 3 1/2 turns out, reverse clearance is .047, can't remember hi clearance but it was well within spec (hi really wouldnt matter much in this case). When I set the brake-at any temp- it don't roll, jerk back or forward, just locks down solid.

I'm with you on the temps..I just don't see that much temp difference making that much difference in release time. On my way home, I'm going to stop and find some Type F before we go racing tonight. That crap is getting damn near impossible to find at Orielly's or Autozone!

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post #5 of 11 (permalink) Old Apr 6th, 17, 2:47 PM
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Re: Reaction Times vs Trans Temp

Well that covers it pretty good.

Only other variable i can think of would be the time spent on the transbrake and heat soak of the solenoid/coil. If you were on the brake alot longer that coil can get hot, still not sure it's 40 thou worth.

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post #6 of 11 (permalink) Old Apr 7th, 17, 8:41 PM
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Re: Reaction Times vs Trans Temp

i was having problem cutting a good light , i was all over the place, found out it was trans brake button. i had the moroso big red button, got rid of it and went back to the ol button i had issue solved, also i would run some type f in the trans good luck
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post #7 of 11 (permalink) Old Apr 7th, 17, 10:55 PM
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Re: Reaction Times vs Trans Temp

you can get STP brand type F at autozone its $6 a quart and is good fluid that is what I use.

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post #8 of 11 (permalink) Old Apr 8th, 17, 4:27 PM Thread Starter
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I'm at Gulfport today, put some valvoline synthetic dexron from Autozone. Temps still get high, but it does shift a tad harder. I've just been making sure the trans is 175-180 before I stage and so far so good. Two races in one day today, got beat 2nd round..took .0133 stripe but broke out 7 thou. Starting second race in about an hour or so. Maybe better luck this time..
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post #9 of 11 (permalink) Old Apr 8th, 17, 4:30 PM Thread Starter
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Pic of my junk and 'Hot Rod' Rodney Taylor's LS Camaro..
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post #10 of 11 (permalink) Old Apr 9th, 17, 7:48 PM
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Re: Reaction Times vs Trans Temp

I am insanely jealous of you being at Gulfport Dragway!

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post #11 of 11 (permalink) Old Apr 10th, 17, 12:47 AM Thread Starter
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Re: Reaction Times vs Trans Temp

Quote:
Originally Posted by rkd View Post
I am insanely jealous of you being at Gulfport Dragway!
Kinda like the place. Going back first part of May for the King of the Coast 2 day race, it's kinda like a party where a race breaks out. Never had much luck there, but Gulfport and Atmore are really the only good bracket tracks left. Hub City is starting to bracket race/TNT on Thursday nights, next one is a week from Thursday..15 minutes from my house

Greg C.
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