1st gear is slipping

[Edd Wadsworth]

I have a 98 12 valve with automatic transmission. It has a BD Exhaust brake, B&M transmission shift kit, and BD torque Converter. I pull a 6500 pound 5th wheel. The truck has always (since I've had it) seemed to take off very slow when loaded. After it gets up to about 5+mph it would take off and go. Coming home the last trip, as I stopped on the off ramp, I didn't think it would get going again. It revved up to about 2000 rpm and barely moved. Once up to 30+mph it seemed ok. Also, driving empty seems ok. What could be the problem, and how do I fix it?

 

[John Dimartino]

I am only guessing,from where I sit,its tough to tell without a road test. I think the torque convertor may not be right for your application,or you need to go with a better quality(big$$) convertor,with better internal vanes.

 

[Strick-9]

Edd,
Sounds like poor torque multiplication (poor TC design) to me, but I'm no expert.

Next time you are loaded down, and you feel the truck taking off slowly. Pull her down in manual low and hold it there. If you can only go ~25mph then you are indeed in first gear and you either need a better TC design or more power. If you can accelerate up to ~40 mph, then you are indeed taking off in 2nd gear and need to talk to a transmission shop about fixing it.

Whoever installed your shift kit should be able to help you fool the PCM into seeing stock valve body pressures.

-Chris

 

[Piers]

If the engine is revving to 2000 rpm it's not going to be a torque multiplication problem. Sounds more like you are getting second gear starts. What's the voltage at pin 31? What is your mainline pressure in drive at idle? Did the B&M kit come with instructions on how to fool the computer to avoid second gear starts. If your transmission shop that installed the kit can't help you, call Steve at 1-800-887-5030

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Piers, BD engine R&D

 

[Edd Wadsworth]

I hooked up today to gain further information. Everything is back to normal. I'm assuming therefore, that I must have been trying to take off in 2nd gear. Today when I pulled it in to 1st, there was no shift change and maximum speed was 25.

I assume that the next time this happens, I can pull it into 1st again. But what would cause this to happen intermittently and what do I do about it. The add ons were on the truck when I bought it, so I don't have any manuals nor contacts. Thanks for the help.