acceleration and maintaining speed issue

mattc113 · Mar 4, 2012

here's the deal, 89 b2, 2.9, a4ld, stock gears with 31" M/T's.
accelerating from 0 to 50-55mph is great, get on the highway, hit 55, and thats about it. i can get it to 65 after about 15 seconds in 4th gear, if i take it out of overdrive into drive, pretty much putting it in 3rd gear, it will accelerate a bit better, but im still not going hardly at all. i can floor it and it wont rev past 3k rpms. below 55mph i can run it right up to the redline through 1st and 2nd.

i dont know if its a clogged transmission filter, bad 4th gear, or what.

never had this problem before, but its done it since i bought it.

mattc113 · Mar 4, 2012

any ideas?

ltuck808 · Mar 4, 2012

Put lower gears in it and find out lol

mattc113 · Mar 4, 2012

well, i had a jeep in high school that had a 2.8v6 and 4.11 gears, and it wouldnt go above 55-60, but i doubt i have gears that low in the b2.

509lifted · Mar 4, 2012

when ur going up hills does it bog down cause my gf truck does the same thing ur truck is doing and its a 87 with same trans and i wanna find out wats wrong with it i hope one of the smarter guys chime in to help u and i both

mattc113 · Mar 4, 2012

if im in drive, i can maintain around 55 going uphill, but my rpms top out at 4200rpms, 3000rpms in 4th. im stumped. going uphill at 35 i can floor it and it accelerates fine, just up to 55.

inuyasha2875 · Mar 4, 2012

have you checked your timing my dizzy came loose and had no power on the highway

mattc113 · Mar 4, 2012

no, i never thought to.

mattc113 · Mar 5, 2012

well, ive checked the timing, its fine, its got new plugs and wires, new rotor and cap, new fuel filter, cleaned the injectors, no vaccum leaks that i can hear or find. only thing left i can think of is the transmisson filter maybe being clogged or the trans cooler not working? maybe the rear diff?

if i cant figure it out soon, i'll sell it and get something highway friendly...not taking the highway adds about 20 min. to my commute.

adsm08 · Mar 5, 2012

Have you considered the fact that maybe you don't want your 22 year old V6 to rev higher than 3000 RPM under that much load? I have found that even with a 5-speed the 2.9 will not go much above 3 grand in 4th or 5th gear. We are talking WOT down the biggest hill in the tri-county area, I still can't pull off but about 3100 in over drive.

I would not suspect a clogged trans filter at all. Generally speaking, given that it's a close system, by the time the filter in an automatic transmission is clogged enough to be an impediment to proper operation there isn't enough transmission left to work at all. It's all slag in the pan by that point.

I would say that your issue is a combination of 2 ( maybe 3) things.

1) Oversized tires on axles that were already geared too high. I know 31's aren't huge, but RBVs were generally over-geared to make them perform better on the EPA fuel economy tests that do nothing to approximate real world driving conditions.

2) Tired old engine. I dunno how many miles you have, but the surviving 2.9s are starting to wear out. They were good strong and reliable engines in their day, but that day has come and gone. The average 2.9 has over 200,000 miles on it with many up over 300. Except for a Detroit or Cummins, most engines are ready to plotz by then.

3) And I don't know if this is the case on your truck or not, but is the speedo was never corrected to the new tires, you may be going faster than your instruments are telling you.

Your rear is likely to have 3.73 gears. All in all, I'd drop her to some 4.10 gears and/or throw a 4.0 at it. That is a stupid easy swap on your B2.

Nathan123 · Mar 5, 2012

I definitely second the inaccurate speedo. I'm running 30's on mine with 3.73's, thats about 3 inches bigger than a stock tire, and when the speedo shows I'm doing 55, I'm actually doing about 59, according to gps. I will say though that mine is an automatic and I can wind out to about 3500 in od on the highway about 80 mph. Downhill the speedos been past 85. When I'm in 3rd though, I regularly get up to 43-4500. I'm not saying this is good to do and maybe my tranny is slippin a bit. But I would definitely find out if your speedo is lying to you or not. Also, acceleration above much above 60mph takes some time.

MJ'sBlkBII · Mar 8, 2012

It is sounding like this is a typical condition. My '90 is the same way with a 5 speed running 28"-29" rubber. I don't remember how my '88 was, as that was over 10 years ago now.

alwaysFlOoReD · Mar 8, 2012

I would agree with all the above;
Tired motor trying to overcome wind resistance.
Oversize tires on stock gearing, probably 3.45 as all my parts b-II [4] have that gearing. I have 4.10 with 31' tires and that's good on the freeway for me to do 75 easily, tho I do have a 4.0 as well.

Richard

mattc113 · Mar 10, 2012

well, the motor only has around 55-60k on it. i bought it from my cousin and actually helped him rebuild it 5 years ago. so the motor should be strong, transmission was rebuilt 4000 miles ago.

i'll look on my rear axle for the code tag so i can figure what gears i have. so its just as simple as swapping some 4.10's or 4.11's? if so, what vehicles should i look for at the junkyard to find 4.11's? i know i can get new ones for around $200, and unless i have limited slip, i'll add a locrite.

all the info has helped so far, just a little more and i'll decide what to do.

mattc113 · Mar 10, 2012

also, if i swap the rear gears to 4.10, will i need to change the front gears as well?

acceleration and maintaining speed issue

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