7.3 turbo auto tranny shifting hard...help!!!

[Cow-man]

Ok first of all Howdy to all!!!
Great to be here!!
Now to the nut Curtin...
I just purchased a 1995 F Super Duty truck with a 7.3 turbo auto tranny.
My tranny is acting up...upon test drive the tranny shifted hard. I mean really hard...so hard that I turned around and went back after 4 or 500 yards. The guy said the tranny was reciently rebuilt...we checked the fluid level and it was low. After giving it 3 qts of blood I tested it again. Shifted perfectly!! Drove it about 5 miles then back ..a total of 10 miles. I bought it...happy with mt purchase. Guy said that he dis loose some fluid when he installed TBE new aluminum radiator but didn't think he lost that much so he didn't check it after install. Well I started home...a 3 hour drive...15 miles into drive the tranny acted up again. Same thing but this time I put a at of Lucas Auto tranny additive in. After about 10 more miles it finally shifted right and did so for the remainder of the trip home. I got up the next morning and tranny still acting as it should. Drove it about 20 miles parked it til late afternoon .started home and once again same hard shift...no over drive ...OD light on shifter blinking.... Got it home and started researching......fone on a forum that in a 1997 model the tranny takes its shift change quest from the tachometer....i did notice that my tech is not working properly....idles at about 400rpm...driving doesn't reach 1000. Is this my problem?. Your thoughts please!!

 

[Shade tree]

If you are losing fluid your tranny will sense a "slip" condition. At that point the tranny kicks up the pump pressure to reduce the slip which also make the OD light flash. The extra pressure may also force oil out some of the seals. Find the leak and fix it.
If the leak is fixed and it still does the same thing, then there are internal issues you have to deal with, such as worn clutches, bad seals, or even valve body issues. Pull the tranny and tear it down and just fix it. About a grand to maybe $1500 to fix it by your self, maybe $5000.00 at a shop. Pull tranny and bring to a shop for maybe 1/2 price. The R&R is a major cost at a shop.

 

[BW42]

Your tranny is probably a 4R100 tranny -- an upgraded version of the E4od, which I have. Check out the videos (16 of them) on Youtube, under TransmissionBench. I rebuilt my E4od last January-Feb (took my time) using these videos, and about $1,200 parts kit from Transmission Bench. I'm a retired opera singer, just today turned 80. Had only one glitch -- inserting a piston using the method suggested, and ripped the new gasket to shreds. Called and got a new one, used my method with great success. A new shift kit comes with the parts kit. Had to buy a pair of snap ring pliers, which I also used to insert one section which was actually two of the sections together. Won't make sense to you until you get into re-assembling, but those two sections together were heavy. This is a big tranny -- 275+ pounds. Check it out -- BW

 

[gnathv]

If your overdrive light was flashing there are codes to read. Find the codes and you will have a starting point.

I see you’re in Greenville, home of Hank Williams and one stop light.

 

[gandalf]

Your transmission is controlled by 3 things on your truck. The first is the speed sensor on the rear differential. It's on the front side of the differential, above the mid-line. The second is the TPS (FIPL), mounted on the driver's side of the injector pump (IP). The third is the tach. All these feed into the TCM, the transmission control modual. If any one of them is out of specs the TCM will throw the transmission into limp mode, causing very hard shifts.

As gnathv mentioned, get a code reader to get the codes. You mentioned that the tach is not working. That alone will cause your problem. It's mounted on the IP gear tower, to the driver's side of center. It has 2 wires. Unscrew it and clean it. If that solves your problem start saving for a new one. Whatever you do, DO NOT remove the IP gear tower.

Report back with your progress.

 

[TNBrett]

Your transmission is controlled by 3 things on your truck. The first is the speed sensor on the rear differential. It's on the front side of the differential, above the mid-line. The second is the TPS (FIPL), mounted on the driver's side of the injector pump (IP). The third is the tach. All these feed into the TCM, the transmission control modual. If any one of them is out of specs the TCM will throw the transmission into limp mode, causing very hard shifts.

As gnathv mentioned, get a code reader to get the codes. You mentioned that the tach is not working. That alone will cause your problem. It's mounted on the IP gear tower, to the driver's side of center. It has 2 wires. Unscrew it and clean it. If that solves your problem start saving for a new one. Whatever you do, DO NOT remove the IP gear tower.

Report back with your progress.

OP’s truck is a ‘95. That means PSD, so no FIPL or IP.