hi, iv got an 86 305 TPI LB9 auto with about 75k miles. no engine work other than a ported plenum and hooker 2055 headers. if i dont pick up my foot from the gas at WOT it will rev to atleast 6500+ RPM. It redlines at 5500 and iv heard the TPI suffers around that rpm i was wondering how high the revs can get before it will cause any damage in any way (excpet to my gas guage). Ive heard the first thing you would worry about it the valvetrain but i dont know that for sure. Also its not held at 6500+ RPM its only for a few seconds at most.

my tranny fluid is not low, could there be something preventing it from shifting sooner?

thanks a lot.

 

The car is meant to only rev to redline. These cars are not Hondas or other 4 cylinder wonders that rev to 8k to make 110hp. They are low rev high torque motors which means that all of it's power is made below 5500 rpms.

Stop revving to 6500. It's bad for an engine. And if 5500 is redline and you are revving to 6500, my question is why? All you are doing is putting retarded amounts of strain on a motor. It would be like me expecting you to breathe oxygenated water and wondering why you are turning blue.

TPI motors stop making power around 4500 rpms in stock form and are done at 5500. The computer shifts the tranny at 4800 or so. LEt the tranny do the shifting. It's been proven to be the best shift points.

Your car has 75k miles which is really really low for a 1986. I would hate to see a post in a week that you blew the motor because you were stupid.

STOP REVVING !!!

 

The first thing you should do is buy an aftermarket tachometer so you can get an idea of your actual RPM. The factory tach is notoriously overly optimistic, sometimes by as much as 20 percent. That means you could be running as little as 5200 RPM at your stated shift point of 6500 RPM.
The second thing you should do is move your shift point down to a reasonable RPM! Stock TPI motors make peak horsepower at 4400 RPM and they make peak torque at about 3000 RPM. If you use the stock tach, you should shift at an indicated 5500 RPM. If you use an aftermarket tach, shift at an indicated 4400 RPM.
Yes, you should be worried about the valvetrain at high RPM, but only above a true 5500 RPM. The stock valvesprings will allow valve float at high RPM.
There probably is something wrong with your transmission that causes it to shift at such a high RPM but it might just be a small problem like a misadjusted kickdown cable. Maybe someone with more experience with automatic transmissions in these cars will post an idea or two!

 

what he means is that on the highway if he digs into the throttle and it downshifts, it sticks at 6,000+ for a few seconds...mine does it too and i dont know why. one time i was stuck at 7,000 for about 8 seconds pretty scary

 

yes, its an automatic tranny and i WANT it to shift earlier. i have to let off the gas to get it to shift at 5500. im saying that if i stay at WOT it will take itself up to 6500+ and i do not like that.

I just wondered if redline was really what i should consider max, because i know u can build a motor to go well above that. before anyone says it, i know that my motor is not built for it, and i now know that ill consider my 5500 redline the max ill let it go.


Also, i am aware that its not supposed to shift to overdrive while at WOT, so for that i let up for a sec. But for 1st to 2nd, and 2nd to 3rd, it should shift at the right time on its own which it wont so i have to let up.

I dont want to let uppp!!! haha.

thanks

 

again, mine does the same exact thing. not sure why, or if it's even something to worry about. sorry i am not of much help other than saying my car does the same thing

 

Yeap, seen it many times myself.

 

Here is a link to the detent cable adjustment article: https://www.thirdgen.org/detent
Try this first and see if it helps, if not try changing your tranny fluid after running some good tranny cleaner(Seafoam?) through it.
If that doesn't do it you should find a reputable transmission shop and ask them what they could do for it. Shop around or get references from people you trust!!

 

You definitely have a tranny problem of some sort. My 700R4s have always shifted very correctly.

 

Hey Guys,

I'm not positive, but my 87 T/A at wide open throttle, is not supposed to go into overdrive. It only goes into OD if you back off the wide open throttle or change the computer. Also, the injectors are supposed to shut down at redline (if the computer has no mods). I would start with that. Good luck...jster

 

When racing i don't let my transmission shift on its own due to the fact that even at WOT, it will shift at somewhere around 2000-3000 RPM. i don't know why, but i do know that it is probably is bad news. Any thoughts?

 

i know the 700r4 will shift out of 1st gear all by itself at 5500 rpms....even if you have the shifter in the 1st gear stop. But I have the same problem with my 2-3 shift.....it wont shift into 3rg gear at WOT. I have to let my foot off the gas too. It will rev past 6k and even bounce off the rev limiter. I know thats something I'll have to play with too.

 

my stock 85 lbp would run first gear to 70mph and shift at 6500-6700 rpms
dont get me wrong it would outrun almost anything around because, by the time the person i was racing was shifting into third i was still in first!

i drove it like that for 3 years and the motor finally blew a head gasket due to the electric fan crappin, the bottom end was still in good condition!!!

BUT, my car was doing it b/c the previous owner shorted the ecm, so instead of buyin an ECM he hotwired the injectors, fuel pump, and distributor to the ignition key!

it made alot of highend power,but with a new ecm and correct wiring its alot more off throttle responsive,and shifts at 5000-5500rpm, altho rich, i was getting 30MPG on the highway at 80 with the HOT wired setup!

just my .o2~~
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damn retarded key board, i ws reffering to my 85 lb9 TPI, 700r4, and 3:23 gears

 

First off get a tach and use it instead of the OEM junk. After that, how's your tranny fluid looking? If it's brownish change it, and the filter. They're pretty easy to flush takes about 2 hours and a buncha tranny fluid. Besides that, you may check the governor to see if it's acting like it's sticking, or to recalibrate the governor. B&M and a few others sell kits to do it. The governor is on the driver's side back of the transmission under the steel cover. It just pulls out after you pop the cover off.

 

unless a mechanical fault, the kickdown cable controls line pressure, and shift pressure, it may need adjustment, my 85 used to have trouble downshifting, it was due to the valve in the transmission sticking. improper adjustment will cause early shifts even at WOT
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i was using my scantool for rpm verification, i put 63,000 miles on my car driving it that way, and the tranny only went out b/c a "mechanic'
put type-f fluid in my transmission! ,the next day the reaper took the tranny!!!

 

Get a scanner or laptop hooked to your ALDL and find out your true RPMs. I thought I had 3.73s, until I hooked my ltop to the ALDL port. Turns out when the tach says 4000 rpms, the engine barely at 3000 rpms.

So, when I'm flooring it, according to the stock tach it shifts at about 6000 rpms, but if I was to check it through the ecm, I doubt its even breaking 4500 .

Bottom line, VERIFY your TACH!

 

My tac is pretty accurate all around. But at WOT when I shift into second, it shows 5500 rpm, but my laptop verifies it really shifts into second at 5000 rpm.

 

I have an autometer tach mounted near my stock tach. At idle the stock tach is off by ~50 rpm, at 3000rpm is it out ~150... at 5000rpm the stock tach is off by atleast 300rpm. Food for thought, my last '88 IROC w/t-tops seemed further off at higher rpms but I never had a tach to check it.

I've always shifted my LB9 around 4500rpm.. seems safe for longevity and still has lots of power. Occassionally I'll slip and rev upto 5000 or even 5500 if I'm not watching what I'm doing, but rarely. Just to be safe I've set my chip to have an rpm limit of 6000rpm. Stock the GM chip has the rev limit set to 10,000!!

 

gm makes a shift corrector kit for the wide open 3-4 shifts that it used in its police package 700r4s

you also do not want to over rev any stock small block because you will pull out the screw in rocker studs and it sucks when they go

 

i had a data logger hooked up to my car...said it was shifting at 6K on my tach but on the laptop it was reading 5300rpm lol

 

my 1985 Camaro Z28 i built a 350 for it, 330hp 380ft/lbs just like the gm crate motor... in 3rd gear it would rev 6000+rpm if i didnt let off the gas to let it go into overdrive... this seems to be a common problem with 3rd gens so maybe its nothing to worry about and just needs a TV cable adjusted?

 

When my tach reads 5700, my engine is doing 5000.

Don't believe your tach. 6500 rpms may very well be the 4800 shift point the car is supposed to shift at. Trannies dont care what the tach says.

 

are you guys listening about the 3-4 shift

its a police package that replaces a valve in the valve body

its also a good Idea to get a new tv valve because they stick in the valve body and cause things like the 2-3 shift problems.

both of these valves and all the gaskets is less than 60 bucks and all you have to do is drop the valve body and HOOK IT UP!

I just planted the seed earlier and hoped some of you would catch on.

there is a lot of people who know twice as much as me on these pages

where do you think I got my info

I am sure you could find a part number by doing a search with the keyword police package- yeah I really dont like the idea of a part to perform suck a key function have a name that performs such a hated function