4r70w for 400hp mark viii
- Thread starter gbradleyb
- Start date
BlackIceLSC
New member
The rev limiter doesn't kick in until 6000+ rpms.
1st gear will reach to 54 mph before reaching the rev limiter so it isn't a matter of "doing it right"...it's mechanical arithmetic
gear ratio in trans vs final drive ratio : engine rpm's = 3-1 downshift. And in a 94-97 transmission, this can spell disaster.
in a drag racing example, most STOCK base model Mark VIII's, when raced 1320 feet in DRIVE will cross the finish line in 2nd gear at approximately 5800- rpm's, depending on wheel speed at launch(traction). 1st gear shifts at WOT at approximately = 54 mph at 6000 rpms.
see this video for an example...
http://www.markviii.org/~firenice/MOV00266.MPG
It isn't like someone will willfully damage their transmission....but if you're getting on the freeway and the onramp is short, and there is a semi coming at you at 55 and you're doing 45 mph so you willfully depress the gas pedal to gain speed, not only is it possible for the transmission to downshift to the appropriate gear, but the wide gear ratio will force it. I'm talking about "in Drive", not manually pulling the gear.
Kirk, it isn't a matter of whether I willfully "broke" my transmission....it is a matter of the transmission has a some weaknesses that unfortunately people don't know about until it is too late. You and many others have just been lucky enough not to have experienced that.
There's a reason Ford re-tooled the 4R70W, and damaged caused by 3-1 downshifts is one of the many.
1st gear will reach to 54 mph before reaching the rev limiter so it isn't a matter of "doing it right"...it's mechanical arithmetic
gear ratio in trans vs final drive ratio : engine rpm's = 3-1 downshift. And in a 94-97 transmission, this can spell disaster.
in a drag racing example, most STOCK base model Mark VIII's, when raced 1320 feet in DRIVE will cross the finish line in 2nd gear at approximately 5800- rpm's, depending on wheel speed at launch(traction). 1st gear shifts at WOT at approximately = 54 mph at 6000 rpms.
see this video for an example...
http://www.markviii.org/~firenice/MOV00266.MPG
It isn't like someone will willfully damage their transmission....but if you're getting on the freeway and the onramp is short, and there is a semi coming at you at 55 and you're doing 45 mph so you willfully depress the gas pedal to gain speed, not only is it possible for the transmission to downshift to the appropriate gear, but the wide gear ratio will force it. I'm talking about "in Drive", not manually pulling the gear.
Kirk, it isn't a matter of whether I willfully "broke" my transmission....it is a matter of the transmission has a some weaknesses that unfortunately people don't know about until it is too late. You and many others have just been lucky enough not to have experienced that.
There's a reason Ford re-tooled the 4R70W, and damaged caused by 3-1 downshifts is one of the many.
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Yea I accidentally did that once...punched it while cruising along and it just wouldn't give me any rpms so I went a little farther and shot right up around 6k. Scared the **** outta me. My tranny doesn't like to downshift for me sometimes when I punch it. Sometimes it just stays in the same gear .
Anybody ever bought a mps tranny? Found them on eBay...they have a 99.8% positive feedback and it's much cheaper
http://m.ebay.com/itm/MPS-HD500-HIG...3D120988005709&_trksid=p2056116.c100408.m2460
http://m.ebay.com/itm/MPS-HD500-HIG...3D120988005709&_trksid=p2056116.c100408.m2460
Lvnmarks
quandoomniflunkusmoritati
I would acquire a 98 transmission, call up BE controls, and buy a rebuild kit & shift kit from him. 20k miles of very hard driving and mine still shifts great.
Although I wish I would have done the tail shaft housing lube mod. I think I have some play back there but I haven't confirmed that yet.
Although I wish I would have done the tail shaft housing lube mod. I think I have some play back there but I haven't confirmed that yet.
KStromberg
Vortech kicked in yo
Some play at the output shaft is actually perfectly normal. There is a "range" that is acceptable but I cannot remember what it is.