I just recently swaped in a 5spd into my truck with a sb dd 3600. I hooked up to my trailer (empty) for the first time since the swap and I have a huge bucking problem.(Trailer is a 24ft gooseneck mainline 14k deckover equipment trailer) I can get the one two shift fine I go for third and the truck starts bucking horibly when I release the clutch to the point you need to either floor it or take your entire foot of the throttle pedal to get it to stop and it does the same into 4th gear. I have it set up that the front of the trailer sits a couple inchs higher than the rear so it sits level towing. Do you think it could be because there isnt enough tounge weight with it empty? I havent had a chance to load it and tow to see if that helps it.
Any ideas to stop the bucking?
Evan

 

i had alot of bucking with our fifth. i lowered the hitch two notches and raised the pin box one notch. now the trailer sits perfectly level when hooked to the truck. i also installed shocks on the trailer and bilsteins on both trucks... much happier..........

 

I'm a little confused reading your post. To me, the first half describes bucking caused by shifting into a gear at to low of an rpm range. The second half sounds like suspension. I suspect the dd clutch is also part of the problem. A dd clutch holds pretty tight and at low rpm I have heard guys complain about similar issues. Possibly shifting a couple hundred (or more) rpm higher might help. It may also be time for some new shocks. I'm assuming you're coming from an auto also. I think your idle speed needs to be in the 750 range.

 

If the bucking is taking place as you let out the clutch and your rpm's are low that just says you are shifting too early. If the bucking is taking place and your rpm's are right for the shift, that says your throwout bearing has a problem.

If those two things are OK and it is not too low of an rpm or not the throwout bearing, then you need to look at how your trailer is set up on the pin and also your shocks, springs, etc. If the trailer is not pulling level, it will have a force toward the low end, that can cause bucking if the front/truck side is nose heavy. It literally pushes into the truck instead of just being pulled. That push-in feeling in turn becomes a bucking situation due to the pulling motion of the truck, then reverse response in fwd push of the trailer. Causes a see-saw effect. From there you also get into the road surface and construction of the road, expansion cracks etc, which amplify the issues.

CD

 

Check the return springs on the throttle linkage. It sounds to me like the throttle pedal is too reactive, and a small buck will cause your foot to start bouncing on the pedal, thus making the buck larger every time. There have been documented problems with this since these trucks first came out in 94, especially when towing. You may have a broken or missing throttle return spring, or may need to add an extra one. Try it, I think you'll be happy.

 

not to hijack...but i experiance a similar problem, only it will do it unloaded also...where can i find what rpm is supposed to be "ok" for shifting??

 

Seems like there were plenty or springs on it when I swaped on in that was on a 5spd truck. Beleive there was 3 springs on the bracket. I will check though. Think I will probably replace the truck shocks and see if that helps to.

 

CD, not arguing but I don't understand how the throw out bearing could cause this. I thought the throw out bearing was only in use when you were disengaging the clutch. Once you engage it and take your foot off the peddle the throw out bearing was no longer in use.

You'll have to determine that for yourself. There are an awful lot of variables that affect that decision. Remember also that the spread in the gears plays a big part. You may shift into third at 2200 but have to wait until 2500 or more for fifth.


Something else that just came to mind. Check your bolts on the hitch and on the GN tube. If I'm interpreting what you said correctly, a deck-over trailer is going to be a little more nose heavy than a standard GN. Any slack caused by a loose mounting or worn parts will be amplified by that type of trailer.