Originally Posted by gregx
I have a 93 geo tracker lsi 4x4 with the 3sp automatic transmission.
Im have a problem with it.
when its cold it will not shift out of 1st gear it just gose into neutral , so when the rpms hit 3500 where it would shift it just gose into neutral.
But heres the thing if you let it run a few minuts and let the temp gauge start to come up it shifts no problem at all with shifting..
I changed the trans filter 3 weeks ago I was thinking it may be a clogged filter.
anyone know why cold no shift warm shifts every time????
no other problems trans.. or 4x4
Myself more partial to rebuilding powershifts but; always complete visual stopped.... Did you check cooler lines and flush;verify no restrictions in cooler lines, kinks or such. Any indications of leakage when you remove vaccum line at modulator?
1) First verify condition exsists in both 2 and 4 wheel. If you can remove governor; check for heavy sludge accumulation and or binding piston servo in governor. You should be able to depress servo with moderate pressure and it should smoothly return without binding! If so closely inspect quille and servo piston.
2) Block all 4 wheels in the air; test "unloaded" wheels and monitor through gradual increased acceleration observing upshift 1,2,3 watching RPM gauge for drop each upshift point.... does upshift occur similar RPM
3) Next test apply light resistance application at both wheels on same axle
(2 wheel mode) does it upshift normally????
4) Next perfom roadtest and monitor RPM'S closely when upshift occurs; accelerator held at constant speed..... what is happening to RPM'S??? Personally I doubt it's going into neutral..... DO you hear any noises or clashing when this condition occurs???? Shifter doesn't actually move.....
5) Testing with pressure gauge may not always be possible but always perform "forced downshift" through 3-2, 2-1 (accelerator closed/"off") monitor for forced deacceleration and RPM increase "surge" when downshift occurs!
6)Test as if it was actually a manual; shifting manually and monitor smooth "similar" RPM'S at each upshift point. What happens on downshift; do you feel engine braking....
You must be specific what is happening to engine RPM if you hold accelerator constant when you say it goes into neutral; does RPM spike or hold????If you suddenly close throttle at 3500 as you say..... does engine brake or coast???
A master has great eyes, ears , and feel before the tools even come out!!
I strongly suspect governor is likely binding most commonly sludge buildup or servor piston wear/damaged seals. Cheapest check before you start shelling out da cash! Next replace modulator; just by service level alone, proper full service and adjustment I replace modulator anyway! If you have a vaccum hand pump test it with vehicle unloaded.... is it holding vaccum and does it have adequate vaccum signal! Even observing operation unloaded wheels will provide answers!!!!
Pump is highly unlikely since the pump pressure would decrease with temp!
If the above haven't resolved your problems hookup pressure test gauge and record "all" pressures; cold, hot,manual and auto upshift and forced downshift tests. I am confused though; thought you mentioned you suspected modulator but never changed it????
Continuing as is; likely trans will be headed elsewhere soon anway but 90%probablity governor servo is binding. You can also trigger upshift wheels unloaded using vaccum handpump as well and test at lower RPM'S to confirm modulator operation.