Login Register

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
1991 3spd auto ""HELP!!!"
#61
(06-26-2016, 05:55 AM)Michtrackerproject Wrote: Ok hello after some time away.. back to transmission questions finally got to drive the 91 tracker on a proper road,, But I have no idea what normal is for these 3spd transmission it seems to not being shifting into 3rd<> and the rpms at 55 are about 4k, what should I be looking for here as for shift points / rpm and final run out at speed .. ie can or if I will be able to drive freeway speeds at what rpms,>?
the shift points are all based on rpm (tail governor device,deep inside) and load, load is vacuum to the vacuum modulator to rear of trans.
there are screens (tiny) that are part of the GOV and can clog.


http://www.fixkick.com/tranny/slush/governor.JPG

the shift points are also controlled by the TV cable, and if it jams out or the actual valve at rear same, shifting will be crazy late or never to 3rd.
as seen here part id 19
http://www.fixkick.com/tranny/slush/slid...-base1.jpg


the graphs for both transmissions are in the FSM.
and here is one.


if on flat ground, and easy right foot, it will up shift fast, due to huge vacuum at moD. (means no load)

and all this stuff above assumes the trans does not slip.
the book shows the graph for upshifts and down.
the 2>3 shift can be as low as 19mph.
if WOT< or max load,
it can be 71mile shift point.
page 28 in FSM chapter 7b

if the mod valve is ok.
if the TV detent valve dont leak
and trans dont slip.
and gov;. screens not packed up.
and if stall test pass.
and if line pressure is at spec.
then it will shift , under no load about 20mph into 3.

thats it . i think, good luck
http://www.fixkick.com
Reply
#62
ok and this is what I have read,, but I cant find what to expect at road speeds for say 70 mph/ rpm/ I realize these can vary upon gear ration in the axle and tires sizes but should I be seeing 3k rpms at 70 mph or 5k rpm at 70 mph... ..if I had some reference id know what to look for,, ..Also I have a set of 5spd axles available ,would this help final drive ratio.. and lower rpms, at freeway speeds.
Reply
#63
that is covered in my axle speed page, it shows, the speed at 3000 rpm in all gears, and all permuations if engine ,trans and axle.
in your case that be this. (stock tires, or not. as that changes speeds, for sure)
the math is easy, i have that posted there, (tire circumference is the 1 variable, all else is KNOWN)

see this page, see that your car is 4.62:1 axle, so that means 3000 rpm is 3rd gear, and 52mph, stock tires, the 8v goes slower with that axle, all do. (compared to the 16v engine)
then see chart 2? for wrong tires. i did the math there too.
17% faster with 33" tires, see that? or 60mph with 33" tires, 1.17x 52...
keep in mind those number are all with the TCC locked up, if not, the TC slips and no man on earth can guess that...(temp and load dependent, is that slip)
http://www.fixkick.com/part-time-test.html#SPEED


now this, ever seen the hydr, schematic of the 3l30
here it is.
see this line marked blue that is GOV pressure out put line this pressure rises as cars speed goes faster, the gov converts tail RPM to pressure on that line, the higher the pressure
the sooner it shifts. but note that it then passes through the MODULATOR to the DRIVE line red.
the modulator changes the pressure on both lines, it can even leak pressure, (fluid bypass) to the pan, and cause late shifting based on vacuum engine load.
this is how this beast works. see scary drawing, here.
http://www.fixkick.com/tranny/slush/slid...age_2.html


so what is the math on 70mph. ???

here is the equation off my gears page. (it's only really just 2 things, axle rpm and tire circumference.) both are know at all times. (tranny not slipping)
seems complex and is not. at all.
and the conversion of minutes (rpm) to hours, (MPH)
lets do that.
what are those constants below. 5280 is feet to mile. , 12 is inches in foot.
and 60 is minutes to an hour.
ratio is

algebra1:
MPH = (((( RPM ÷ total ratio) X circum") ÷ 12) x60) ÷ 5280

stock tire is 85.1" circum. a fact, no guessing, one can even use a tape measure to prove that. (or C= pi x D) (D is tire diameter outside , not rim)

total ratio in Locked up 3rd gear is 4.62, same as rear axle ratio. tranny is 1:1 in 3rd gear 1spin in, and 1 spin out....
that means engine spins 4.62 times to get 1 turn on axle. (or if engine pins 4.62 times, axle turns turn only)
easy no?
why not just do 6000 rpm max rpm? we already know 6k , its 3k times 2.
that be 52 mphx 2 , or 104 miles per hour,at k6 RPM after all 3000 is 52 and 2 times that is 6000 rpm.

but what is 70?, well one could do the equation or just interpolate that, it's a linear function.,

using interpolation shows 4038 rpm. = 70, in 3rd gear, locked up.
as seen here. pump in 4 numbers and bam. 52,104,3000,6000 equate.
https://www.easycalculation.com/analytic...lation.php
now lets work that backwards

as we did in the old days with teacher swinging a ruler,,,, Class show you work or get zero credit....
4023 div by 4.62 is 874 axle rpm
so 85.1" circum. is 74379 inches in 1minute. (all done on a 4 banger calculator)
div by 12 is feet a minute. is 6198 feet per minute (getting closer)
and x60 is feet per hour or 371898 FPH (feet per hour)
divided by, 5,280 gives. me 70.4mph.(feet to mile)

there i did the math both ways, by equation and by interpolation.


answer was,, 4038 RPM.


you can hear and feel all 3 gears
and the TCC lockup.
and unlock,
all but unlock are predictable RPM.

this car is no 300hp Chevy that pulls, 3;1 axle gears, not by a long shot.
http://www.fixkick.com
Reply
#64
plan on running 235/ 15's ,and I got my ratios backwards ,, I would need to go to the 430 gears to get a decrease in my rpm.. the 512s will only make it worse, ,,.. is there anyway to check the ratios of the gears without breaking open the diffs,, being as I have no clue what's really in this truck, axles and t case wise.. all I am sure of is that the chassis and axles seem to be factory. LSI 1991 2dr auto, 1.6 8v not original, trans not original, "I just changed it," from a 91 92 2dr auto, supposed to be a body plate that should have some info ,,, any way to find out the ratios if the axles are original would be nice.
lastly . .. the detent/ kickdown / TY cable .. all the same cable just different names here ? if its the same then I have yet to connect this still trying to get the cam and lobes from a donor,
Reply
#65
ok, got a chance today to drive this, no traffic, so I was able to watch the rpms/ mph. and it is as close to 3k at 55 mph as it can be seem to be its at about 2900 rpms, when I let out of the gas to maintain road speed at 55, so if all the stats are correct then I seem to be exactly at the ratios for the 4.62 gears and the 3spd trans,, so I feel better about the speeds now, I figure if its at these numbers now on the stock 205/15 tires then I should see a better ratio with the 235/15s. thank you again for all the info, so far so good,, next the idle issues and the o2 sensor...
Reply
#66
there is no best ratio's
it depends on what you do with the car
off road, or on .?
the ratios are set for on road, and max torque, of the engine.
the car can do near 30mpg fuel usage, on the road, driven, at (sane speeds) 60?
this car is a top heavy (high CG) box kite, that does badly in buffeting winds...

look at the engine hp and torque curve, all that needs be known is that. for gearing.
and this engine makes no power at low speeds, its just a lil, 1.6L
and 80hp max.
best is to just forget rpm,, its doing as it was designed to do
and the 3sp is waste, if you drive it with lower axle it will wont to down shift to 2nd every time you roll over speed bump or a dime.
be a real pain a car like that.

the axle gears is easy to measure,

here it is on my page, 1 tire off ground.
http://www.fixkick.com/index2.html#axle-count

the trick is not let the other wheel spin, and to us the 2:1 ratio of the spider gears to help you.


max torque is 3000 rpm
max hp 5400.rpm

this tells you where it runs best fast. at 3000 so car n pull hills and not , have to go to 2nd gear and then scream like mad and suck fuel.


hope that helps...
http://www.fixkick.com
Reply
#67
if you know what the car had new, transmission
this should be easy
stick console looks like stick NO CABLE HERE, so is 5speed and 5.12 ratio axle. engine turns 5 and axle 1 time.
the 3sp has no OD lamp nor P/S power/speed switches, so is 3sp , + cable shift
the 4sp has OD button /lamp and P/S switch shifter console with cable drive,,, and a TCM under the dash,, very telling that.
knowing this,
we then see the 3 axles. below: USA
and next all axles sold world wide here, most are unobtainable now.... see text file.

all this is off my tranny pages.
5sp in usa is 5:12
so is the 4speed, same ratio axle.
and the 3speed runs 2 axles here, one for each engine size , 4.30/4.62 (16v /8v respectively) 80hp is 4.62.


shows the 3 axles in my table and the total ratio , on each in top gear.
http://www.fixkick.com/part-time-test.html#SPEED


the world of suz, axles, most never used in USA ..
http://www.fixkick.com/specs/all_axle_ratios_list.txt


the easy way to check, axle ratios is with chock. marks, one tire off ground, its super easy to do.
http://www.fixkick.com
Reply


Forum Jump:


Users browsing this thread: 5 Guest(s)