GM 7.5 Q's

[DCG]

Problem with the 7.5 isn't the axles breaking, its the small diameter pinion that breaks and/or the ring gear.

 

[usetaboost]

Well I don't think it's so much an issue of a 7.5 not being strong enough, I think there may be another issue. You say you have bad wheel hop. DOne anything to cure this yet? Do you have a rear sway bar? How are the bushings in the sway bar links and lower and upper arms? I find it hard to believe that 400 is the cause of the rears failing. F bodies got those weaker rears and like said before there is plenty of power coming from those. Stock LS1 cars are running 13s with good drivers and lt1s are running low 14s stock. If you wait it out, you CAN find an 8.5 for around 600.

 

[lone racer]

i have been aquireing things,i now have a rear sway,air bags,and 3way adj shocks/F/R, also today i was test fitting my shortened bumper and noticed play with the body mounts so that will be addresed,from there im not sure if the hop is still going to be an issue i think with some tweeking the psi in the bags it should b ok,the only thing left is getting front springs still un sure what to use im going to wait till the car is driveable and get it weighed 3 diff ways front/back/total to help determin the right spring.

 

[Pronto]

New stiff control arms and bushings would help stop wheel hop. Best to take care of that real fast or you will break the rear end.

 

[lone racer]

i also boxed my stock control arms and installed polly bushings allready,the front springs have a lot to do with transfering the weight but my front dosnt raise at all, i know the springs are wrong,its almost at top travel sitting still,when i jack the front up the body only comes up 1 1/2 before the tires come off the ground ,but will address it along with everything else,before its ever beat on just to be safe,after that????well se im going to take it to the track asap to see how bad the hop and lack of weight transfer reall hurt my time,it would be awesome to pickup 3/10ths maby more concidering hopping to the 1/8 and beyond,iv also got another issue i need to figure out seems to (hold back) on top end may be fuel related, recently got a holley 770 and need to tweek it or fulepump is loosing pressure up top? hopeing to have it going in the next two weeks,bringing my rear end to DTS monday have them set it up and go from there.

 

[Pronto]

Wheel hop to the 1/8?

 

[Madcat455]

Problem with the 7.5 isn't the axles breaking, its the small diameter pinion that breaks and/or the ring gear.

I'll give a big +1 for that.

I put a stock 74 Buick 455 in a 84 Cutlass.... stock everything, so it wasn't putting out much HP... but it's the torque that killed the rear. Took 2 months for the pinion to let go though, with street tires and occasional track time.

I was probably at 350HP and 490TQ (love the buick)... ran 13.8's in stock form.


address the weak ring, pinion, and carrier (I grenaded the carrier)... then it may hold up. Otherwise, it's just a matter of time. You'll probably get a decent amount of time out of it since it's being gone through before you run it.... Mine was just thrown in because it had 3.73's in it.


BTW... after that, I went to a 68 Olds type "O" 8.2 rear with 4.10 posi... that thing never missed a beat(5yrs for me and then sold to a guy in TN building a 68/9 GS), even when I built the 455 running high 11's on it on slicks... and it wasn't gone through one bit, just pulled out of the junk pile and threw it in with new fluid


Good luck, I hope you can make it work.

 

[lone racer]

yea no wonder im breakin 7.5s,untill i can get a 8.5 they will just have to do..besides it dont hop that bad on the street,its just the track is so sticky it makes it worse.Thats when everything goes bad a week or two AFTER takeing it to the track. NO more track till ALL mentioned fixes are applyed,then 13.5 or better.

 

[lone racer]

Madcat455, i did 13 passes last year consistant 13.80-81-82-83's with a basicley stock low 8.2 compression 400,and horrrible wheel hop hopeing once my issues are fixed it should run 13.5 or better

 

[lone racer]

also that was with a 3;73 gear floating the valves way before the line,going with a 3;42 should get me better mph and keep me from floating before the line,if not in going with a taller tire to help

 

[Pronto]

Look at some lower control arm relocation brackets. So you've busted the 7.5 before this?

 

[lone racer]

YEA, they were both junk to begin with one was loose as a goose! (worn out)and the other was howeling when i got them,i dont drive it alot,they lasted as expected,again i know wheel hop was the MAIN reason for breakage,along with everything else stated above this year SHOULD be diffrent, if not hopefully by then a 8.5 will be in the works