Need help

[FBCoach]

I use an 05 suburban to pull my boat. Had a rebuilt transmission put in. Now it will not pull the boat out. Goes to around 2000 rpm and just sits. Doesn't spin the tires or even attempt to. Never had a problem pulling it out of much steeper and longer ramps before. Seems fine with regular driving. Any ideas?

[mnpracing]

sounds like it's not shifting all the way down to first gear.

[ericinmich]

Need a bit more info, but I'll assume that it drives normally in all other situations.

If this is true, then it's likely the torque converter. The torque converter has a stall speed which is part of it's design. If you press the brakes firmly and hit the gas, the stall speed is where the engine revs. To low of a stall speed and the engine will not be producing enough HP to pull up the ramp.

Was the tq converter reused or was it a 'new' one with the rebuilt trans. If it came with the trans, it probably has too low of a stall speed.

edit: or as posted above, it may not be getting to first gear. Did you pull it down manually to 1st gear?

[FBCoach]

sounds like it's not shifting all the way down to first gear.

That's what it feels like, but it seems to start in first under normal situations. Is there a sensor that determines what gear is needed?

[FBCoach]

I have no idea if it is the same converter. I will call the place that did the repair. I did manually put it in 1 with the same result. Got home and set the parking break and floored it and it went to around 1800-2000 rpm and sat there.

[mnpracing]

That's what it feels like, but it seems to start in first under normal situations. Is there a sensor that determines what gear is needed?

yes, should all be electronically controlled. But, as ericinmich mentioned try manually shifting down into first (On my truck, I can go to 3rd 2nd or 1st manually on the gear shift lever)

[laserfish]

Don't know if this applies to this vehicle/year but did this on a 99 f150 and had to readjust the gear indicator. Showed it in D but was in N. Could it be you are showing first but really in second?

[ericinmich]

A stall speed of 2000 is about right for the 4speed GMT800 series of trucks. So, I guess I'm saying ignore probably ignore my first post. There is another factor in torque converters which is the K factor (tq multiplier) that could be wrong if the wrong part was used but I doubt it if it drives generally OK.

I would suggest being sure it is getting first gear (get bluetooth CAN bus adapter to talk to phone or tech tool or mechanic). Then ask about correct torque converter. Then dig into why motor isn't producing power.

[FBCoach]

Update. Took it to the mechanic that did the trans rebuild. He hooked it up to the computer and it is saying that it is not going to 1st when under a load. Even if you drop the gearshift to 1. They have no idea why and are looking into it.

[IDBoating]

Update. Took it to the mechanic that did the trans rebuild. He hooked it up to the computer and it is saying that it is not going to 1st when under a load. Even if you drop the gearshift to 1. They have no idea why and are looking into it.

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[Stingreye]

FBCoach. Its completely unrelated but if you are grasping at straws maybe this will help:

My motorhome is a 2000 Ford V10 F53 chasiss. I had a really bizarre transmission issue.

Only under load up a hill, it would fire off codes and the OD light would flash. The transmission temp gauge never read high and it was only an issue in first gear coming from a dead stop.

I paid two mechanics to look at it with no help. I replaced three different sensors. Still no help.

I finally found a posting on a forum somewhere where there was a ground harness update for the ECU. The ground harness is no longer offered by Ford so cut 7 pcm ground wires, created a new separate ground location, and grounded these wires separate from two other ground wires there.

It fixed the problem. Apparently, with these electronic transmissions, the noise on the ground was getting to the ECU telling it the RV was going 30 mph which then caused the coach to start in 2nd gear. Then the trans speed sensor thought the transmission was slipping really badly and spit out a transmission error code.

Long story short. Its amazing how many problems can just be poor grounding with all the electrical stuff on these motors.

I really doubt your issue is the same as mine but when the problem happened the engine power felt like crap because it was in second gear. Again only happened under load (on a hill).