Is it just the tires

[oldtoyboyd]

I pickup up an 89 1/2 ton burb 6.2l/700r/np241/3.73
The truck has good pickup off the line and all the way up around 55.
After 55 it just doesn't have that much and will hardly do 70.
The truck has 33" truxs mts and I am wondering if these are just too much for the truck. I am thinking of going 31s. Haven't had many 6.2s just gas motors until recently. Tell me what you experienced 6.2 guys think.

 

[kennyw]

3.73 gears and 33" tires with OD 700R4 puts you at 1900 RPM... that should be the sweet spot for the motor. I would say the motor is probably getting tired if you can't hold 70.

 

[Wrench]

I would do new fuel filters and maybe advance timing a hair to compensate for a worn chain. Bet it'll make a world of difference . . . .

 

[6.2Blazer]

I would do new fuel filters and maybe advance timing a hair to compensate for a worn chain. Bet it'll make a world of difference . . . .

My first thought was also changing the fuel filter and the air filter if you haven't recently. My '90 K5 never had a problem maintaining 75 mph on the freeway with 3.73 and 32's, and can't imagine the slightly larger tires would make much difference.

Also make sure the trans is actually shifting into overdrive (4th gear). If it's stuck in 3rd than you might be hitting the governor. On mine the trans indicator (PRND21) had been misaligned for a long time so you actually had to count the detents when shifting from park to make sure you were OD.

 

[AJMBLAZER]

What they said. I just put 32's on mine and wish I had gone to 33's. 6.2L C-code, 700R4, and 3.73's and even with the 32's it still seems a bit low geared.

This thing must have been a screamer with the 235/75R15's it came with stock.

 

[oldtoyboyd]

The trans is shifting in overdrive. It has a filter assembly installed before the lift pump and then a stock filter on the firewall. Would the pre lift pump filter give it too much restriction?

 

[oldtoyboyd]

I put a new fuel filter on it, removed the secondary filter someone had added before the lift pump, and bumped the timing a little. We will see how she does on the way home.

 

[Russell]

If my old bush truck with a worn out 6.2L with a cracked head, 5 speed manual transmission, 35" boggers and at best 3.08 gears could run 60, your truck should be able to do 70!

 

[oldtoyboyd]

Totally different truck. It was nice to actually let off the go pedal because of traffic instead of causing traffic. I guess I'll put 4 inches under it and leave the 33's on it now.

 

[Wrench]

Sweet, good to hear :-) good luck with the new toy . . .

 

[oldtoyboyd]

I went to leave work yesterday and the torque converter bolts backed out. No sign of locktite on them. Luckily I tapped the converter and used the other 3 holes with new bolts. Now my drain plug on the filter setup is leaking. Anybody know where to get replacements these days?

 

[84zz4ss]

Last time we needed some plugs I got the from GM. My cost was around $8.00 each.

 

[oldtoyboyd]

If you could find a part number it would help greatly. The GM dealers around here that we use could benefit from a parts guy if you know what I mean.