1970Firebird

I have a 87 IROC with 251,000 original miles on the entire drivetrain. The only thing that I had to replace besides lame water pumps was the MAF and the injectors.

I performed a fluid/filter change on the 700R4... and didn't see much metal in the pan. The tranny fluid looked a bit "auburn"...but it didn't smell burnt and the transmission shifts right on time 1-2 2-3 R and Overdrive all function without gaps and/or slippage. I decided to bite the bullet the other day and have the transmission flushed = without the cleaner pumped throuh...just the fluid. The guys at the shop starred in awe when I told them the mileage of the car... they swore that it appeared 51,000.

Am I taking a risk here??? Not sure of the risk since the tranny has been operating and continues to operate almost flawlessly and not much debre or metal was in the pan the last I changed the filter 3 weeks ago. I would like to hit 300,000 before I rebuild the whole car. BTW...the IROC isn't burning any oil and my compression is even across all cyliners---thanks to Castrol GTX 10-30.

Z28cross-fire

You should be fine, if anything it'll help.

1970Firebird

I just did some 0-60 blasts

1st run from dead stop @500 rpm. 8.0 sec
2nd run from 5 mph roll 6.8 sec


**** If I dead stomp the car on idle...I lose about .5-.7 ths from tire spin. I can easily see with practice...that I could nail the stock 7.0 sec or better by power braking to 800 rpm on launch and that's on a 250,000 mile LB9.

It seems that there is a bigger hole on my 2-3 shift if I leave off idle..as compared to on a roll. It doesn't feel like the tranny is flaring..but that the engine shoots the RPMs...to quickly and has to recover from the 3:06 transmission gearing that is too steap. If it were 2:73...the car would probably be easier to nail 60 in the 6.8-7.0 range.

Z28cross-fire

Actually if you had the right suspension it'd be harder to get a better 0-60 time with 2.73's. That's why a lot of people upgrade to a higher gear and make the suspension better. So their power goes straight to the ground and doesn't get lost in spin/suspension give/anything else.

1970Firebird

eventually when I rebuild this car...I will be upgrading the dif to at last 3:27 gear ratio (some fuel economy). Taking the car for the 3rd day to work on stop/go driving on freeway..the tranny seems to be shifting a tad smoother. No flaring that I can tell.

KillerRS

I wouldnt flush a tranny with over 100k miles. you are taking a risk of loosening up some debris that has found itself at home in some of the passages, and lodging it an someplace that will cause a failure in the tranny opperation. If your tranny is in good condition i see no reason to do anything else other than a filter/fluid change, not a flush Also a little browning of the fluid is fine, and is usually expected after alot of miles on the tranny. What you dont want to see is a dark brown/black with a burnt smell. I have heard of at least 2 cars that have opperated normaly before a tranny flush, and lost reverse of all forward gears. Im sure some techs will try to sell you a flush though, **** hook up a machine, add 14 qts. of fluid and walk away

92rsbowtie

so the fluid has never been changed? if thats the case, do not flush it. that fluid is probably the only thing holding the tranny together. if you flush it, it might run fine for a while, but it will go out a lot sooner than if you where to just leave the old fluid in it.

1970Firebird

in the 160,000 miles that I had put on the vehicle.. i had done tranny service at least 5 Xs and had it completely flushed 4xs.

KillerRS

alright then if you have done it before, than what eould stop you here? i dont quite get what your saying

1970Firebird

poster after poster recommend to not flush a high mileage tranny period. thats what I am getting at.

85blackberlinet

do your self an find an old head chevy guy that know trannys they will charge you like 300 to rebuild it.