I have a 94 topkick with a cat 3116 and ally auto. It does 55 mph wide open, maybe 60 wfo downhill with tail wind. Can anyone tell me if I can get any additional speed? I already put new tires on (had 9r and I went with 10r but only 1-3 mph change noticed). The truck is great, it pulls good, runs great, has 578 rear and 4 speed ally, 170 or 175 hp stamped on the valve cover. I hate to sell just because it is slow, but it is really slow. 2300 rpm at wfo 60 mph. Please help?????

i had a 90 topkick it would do 65 flat on the floor WO. that was with a fuller 5 speed 2 speed rear. if you want the auto to run faster maybe try a georgia OD. on a side not it was 13900 empty and loaded with the trailer it was 70000+ ran bout the same no matter how heavy. what gvw is this truck?


on edit is it limited by rpm or by a speed limiter? my truck was nice but no tach. 14 years we drove it by sound. does your have a tach?Edited by: chevmeister

I do not know if it is limited by rpm or speed, how do u tell? My gvw is 24980. I have not weighed the truck alone, my trailer, dozer and rig weighs 35420 lbs full of fluids. My truck is slow no matter the weight, unloaded or loaded it does not matter.

Sound like it is RPM limited. I would not call it slow per say, just a limited top speed. Short of changing axle ratio or OD there is little you can do.

I recently bought a 96 Chev Kodiak dump truck (same as topkick). It has the same Cat 3116 engine. Boy is it slow. I don't think it will go over 50 mph. After I drove it home, I thought something was wrong. Maybe it's just the nature of the beast.

i'm not sure if the chevy's operate the same as the IH vehicles but we hookup the ez tech (laptop) to these vehicles and change the top cruise speed as per owners request. they're responsible for any tickets though. check with your service advisor and he'll tell you the cost if any. it only takes less than half hour to do.

i have a 95 T/C, 3116, 5sp stick. 73 mph w/approx 20k gvw and still has some more! with 220,000 i don't push to hard. i did notice when i first got this truck the acc. cable was adjusted to 75%. I re-adjusted to 100% WOT.

I think I figured out why my Chev Kodiak is slow. The rear differential is geared to something like 5.37 or something. The vehicle is designed to push snow. Not to break the land speed record.

578s are going to make it real slow. Look for taller gears or perhaps even a two speed rear.

Iv got a 1994 tandom Topkick with the 250hp cat engine and 6 speed allison. Iv had it doing something like 120km to 130km empty. It has the 4.88 gearing though.

Rev limiter on the Cat being triggered from the TCM speed signal. That cat should rev all the way to 2300. A good tech can bump up the max speed setting.

Clark,

There are several factors by which the manufacturer is required to limit (governor) an commercial truck. Max RPM on the engine (with a very tall differential ratio), tire manufacturer maximum speed, and transmission limits due to high torque input, to name a few. It would be well advised to look into thoses before you make any modification, to prevent a seriously dangerous or costly condition.

On the other hand, should all of the above prove to be well within safe operating conditions, you can get a different ratio or two-speed differential gearing put it. An alternative would be to get a gear splitter (overdrive) added to the back of the auto-trans (check GearVendor site). If you still intend to push a snow plow, lower the rear ration for non-seasonal use to raise your top speed, and add the gear splitter (underdrive) to plow. This will provide you with the best of both gear ranges without compromizing one or the other.

Radio Flyer

What about more power before the speed limiter? I drive a 99 Gmc 6500 roll back that is totally guttless. I get blown away by pick up trucks pulling loaded 3 car trailers when I only have one vehicle on. Not sure which CAT engine is in it, I think 235 hp or something like that, mated w/ a 6 spd manual. Any ideas?