More boost or not?
04-19-2015, 05:57 AM
#21
3rd Gear Member
Join Date: Jun 2010
Location: RI
Posts: 690
The input shaft on a 5r55s tranny is only 5/8 of an inch in diameter. Easy to twist and pop. The internal parts are also very small too.
Ford auto trans model numbers actually contain best case estimates of the breaking point (i.e. when the bands and clutches will let go) - the 55 in "5r55s" actually stands for a max of 550 lbs of torque. A "4r70w" is estimated to be able to take 700 lbs of torque. Those are flywheel numbers. Input shafts can break well before those numbers though.
Ford auto trans model numbers actually contain best case estimates of the breaking point (i.e. when the bands and clutches will let go) - the 55 in "5r55s" actually stands for a max of 550 lbs of torque. A "4r70w" is estimated to be able to take 700 lbs of torque. Those are flywheel numbers. Input shafts can break well before those numbers though.
04-19-2015, 10:09 AM
#22
5th Gear Member
Join Date: Sep 2010
Location: IN
Posts: 2,248
Gotcha Bro, Thats why I joined this site. I can Tell you what a crotch rocket can handle (pretty much anything short of a grenade) but Im new to modded cars. Im at 9lbs boost with 496 rwhp, I can go up on boost but I cant find consistent numbers on tranny and rearend limits. My mechanic says Im close to having to worry about tranny, rearend, suspension etc, but said I MIGHT get away with more boost. I dont want to get to where I have more power than I can use without breaking something.(again) Ill be easy on the highways, and I havent had a chance to WOT launch from a dead stop, Im rarely home to even drive this car. I just want the car safely maxed out for what it has already. Its gonna be a run around car with occasional weekend warrior drags(1/8 mile)
04-22-2015, 12:28 PM
#23
1st Gear Member
Join Date: Nov 2008
Location: Michigan
Posts: 117
I used to have an 07 with the Saleen Supercharger and I had to have the tranny rebuilt twice. I sold the car shortly after the second time. My nephew has a 06 with a roush SC running 15 psi. He replaced it three times. His last tranny (5r55) only lasted 1 month. Only once at the drag strip. He finnally switched it out for a 4r70w. I wouldn't go smaller than a 3.4 pulley until you are ready to replace the tranny.
04-23-2015, 01:58 PM
#24
5th Gear Member
Join Date: Sep 2010
Location: IN
Posts: 2,248
I have the stock tranny and havent had any problems yet but if i do i look at as a chance to something better. Ive swapped my input shaft and I have a deep tranny pan. There are things that i do that i think makes a difference. When staging I always put my caar in second. OD is off most of the time when im driving and i never do kick downs at highway speeds. I know a guy thats gone through his fare share of trannies and he isnt nice to them at all but he has the money so he doesnt care
04-25-2015, 09:55 PM
#25
5th Gear Member
Join Date: Aug 2007
Location: Hollister, CA
Posts: 2,041
What type of pistons did you use, specs? Do you know if it was stock stroke? I'm wondering what the compression is, maybe we could figure it out.
Last edited by loots06; 04-26-2015 at 07:28 AM.
04-26-2015, 11:49 PM
#26
Thread Starter
Join Date: Feb 2015
Location: none
Posts: 12
All I know is car has 45 more hp with new motor than when the stock was in it. It should be the same bore.All we did was grab another block and rebuild from there. It diesnt dtate what brands or even that they ate forged parts on the receipt, but i know this guy and can find out hes pretty straight up from what ice been told and previos dealings with him . Im kinda shocked atmy hp considering the high stall and low boost??
04-26-2015, 11:51 PM
#27
Thread Starter
Join Date: Feb 2015
Location: none
Posts: 12
I dont know ill have to ask my mechanic, he builds alot of street rods and drag cars. He just told me that it has high compression, and puffs a little black smoke when hitting hard.
All I know is car has 45 more hp with new motor than when the stock was in it. It should be the same bore.All we did was grab another block and rebuild from there. It diesnt dtate what brands or even that they ate forged parts on the receipt, but i know this guy and can find out hes pretty straight up from what ice been told and previos dealings with him . Im kinda shocked atmy hp considering the high stall and low boost??
All I know is car has 45 more hp with new motor than when the stock was in it. It should be the same bore.All we did was grab another block and rebuild from there. It diesnt dtate what brands or even that they ate forged parts on the receipt, but i know this guy and can find out hes pretty straight up from what ice been told and previos dealings with him . Im kinda shocked atmy hp considering the high stall and low boost??
04-27-2015, 05:29 PM
#28
5th Gear Member
Join Date: Aug 2007
Location: Hollister, CA
Posts: 2,041
It would be interesting to know what internals were used. There have been some pretty nice results with higher compression and lower boost. I'm gathering parts for my build and I'm using boss rods and Wiseco pistons, compression is gonna be around 9.8:1.
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