Bruno hot and brake won't hold

I know this topic has been covered but i'm looking for any ideas I can get. We have a 2900lb roots wedge promod launching at 4100rpm on an air throttle with 7 psi of boost. It runs 4 teens in the 1/8th and we cool it with a blower between rounds. At the last race the brake started creeping a couple inches and then it would hold. We checked the air solenoid and pressures on everything. By the first round the air density got real good and the car pushed through the lights and redlit. Bruno says the redline synthetic ATF is the problem.Apon teardown we found the fluid is burnt/stinky and the band and drum look perfect. I know from experience it takes over 300 deg to burn redline atf. Regular ATF probably would've caught fire at those temps.

I know most guys use a two step maybe in conjunction with the air throttle. Would that keep the temps down and make the torque load less on the band/drum?
I've also considered a cooler and oil capacity increase but my car is heavy and thats a last resort. The fluid temp readings have been crazy since I got the BRT and Bruno says he doesn't monitor them so i've just been cooling the convertor until I can hold my hand on it between rounds.
Our convertor slips 12% downtrack so its making a lot of heat going 173mph at 2900lbs. Maybe have to change the fluid more often? Thanks Mike

 

I'm not to familiar with the Pump on a bruno drive but can't be to much different than a lencodrive, but I'd check the pump gear and how much engagement the converter neck has on the pump gear. you could have to much engagement on the gear and it's (the drive neck on the converter) is hitting the housing in the trans and tearing it up which in turn equals bad oil flow, low oil pressure, heat and a big frigin mess of wasted money. Clean out your valve body while you're at! all the shavings and crap are probably stuck in the valve body as well. look close at the pump gear and the wear marks from the drive neck and see how much engagement you're really getting.

Just My .02 lousy cents worth of help.

 

i had my bruno starting to creep alittle.i always change the band twice a year, once in the spring,once midway through the season.the band always looked good but it was'nt holding.also the drum looked good but when i pulled it out it had wear on it,dipped or concave,in the center where the band runs,changed the drum and band worked like new.we also use hydraulic fluid in the bruno,takes the heat alot better.we have ran the stall from 3500 to 5000 rpms.

 

Just checking to make sure, do you have a loop line for the cooler inlet and outlet fittings? You have to complete the circuit whether you're running cooler or not. Air pressure on band piston at minimum 200# and fluid pressure adjusted to minimum 150#? The synthetic ATF works on a Lencodrive but I think Bruno recommends straight F type as it holds better for the brake band. I've used both F and hydraulic fluid and they seem to work equally as well. Do you feel like the convertor is working like you want, that seems like a fair amount of slippage, got to be where the heat is being generated. Just scratching for ideas.....

 

Just a stupid thought but i wonder if the exhaust could be pushing the car forward until the sprag in the lenco seats? Cause if the car does stop, why only a short movement? A track we go to has a good slope before the burnout box, and w/ the car off i leave the lenco in the forward gear so i don't have to hold the brake....it rolls a LITTLE bit, then stops. We always ran synthetic too, but Type F might be a good idea.

Mike if you end up buying a band, just come over and get some. I think it's a 400 or AOD low/rev band. Give me a call.

Josh

 

Paint Guy, or anyone else with Bruno experience, do you know if there is any difference in the bands which are available out there? I haven't verified it yet but I've been told it is a band out of a 400 so I'm just wondering if there is any difference in say getting a band from Bruno versus the local transmission shop? I'd just call and ask Bruno but every time we've called him with a question he acts like we just ruined his day........and I hate ruining someone's day.

Joad Donnelly

 

bands

Nice tech. support, That leaves Bruno off my list. Fuck ruining his day. Don

 

I know there is a little movement in the drive line components since you're locking up the input side of versus the output on a convention tranny type brake but I really don't think that is what was going on here. On the previous runs the car would have a few inches of forward movement but then it would grab & hold solid. On this last run it just felt like it was just straight over powering the brake. Once I brought the rpm's up it started moving forward with a deliberate movement. It didn't jump or anything, just pushed through. I'm thinkin' I could have been about .000 on that pass if they would have activated the tree on time!

Joad Donnelly

 

joad,yes its a 400 band .when you buy just make sure its a good cavlar band not the stock,cheap one.bruno also told me when the trans brake is on it holds the motor ,but not the car,so the car can still roll.may need to hold the brake with a linelock or hand brake.

 

When calling Bruno for advice, ask for Bruno Jr. He's a little more friendly for giving advice.

Josh

 

customer service

Don, I bet you could show him the carb trick !!! frank

 

Thanks for all the replies. The plan is to raise the co2 pressure to 250psi install a bigger/deeper oil pan and launch with the 2 step in conjunction with the air throttle to control boost and keep the temps cooler.

BTW Joad is the driver,i'm the guy that surfs the net looking for speed secrets!

Mike

 

Bruno

When you call Bruno, you do need to talk with Bruno Jr. Bruno Sr. acts like your imposing on them by calling in. If you have any problems, call Rod Burbage at Spec Rite Torque Converters in Redding, California, Phone number (530)243-8300. We run a bunch of Bruno's here on the West Coast, Rod builds most of them as well as some of the baddest converters in the country and the fastest in the country. Hope it helps.