Higher RPM's... Torque converter or Transmission issue?

1993 4Runner 3L, Auto, 4x4, 160K, Tran cooler. (Had this for 8 years.)

I am noticing much larger variations in my RPM while maintaining constant MPH then I did in the past (true with cruse on or off).

When driving a constant speed, say 65mph in overdrive, the tac reads

2600rpm when driving in flat no-load conditions.

When I come to a hill the tac will clime to 3000rpm (a 400 RPM increase) as throttle is needed to maintain the same speed (true with cruse or foot).

The RPM's a few years ago, unless my mind is playing tricks on me, would change only 100 or 200 RPM as throttle was added. Now days it is a good 400 RPM increase.

At some point the transmission will down-shift out of overdrive just fine... no issues there. I just notice the higher RPM's before the shift... AND I think I notice higher RPM's after the shift (do not have good numbers on this however).

Do I have a problem coming? Is my torque converter unhappy?

((FYI... in the more distant past I was having the tran temp light come on a once or twice a year when driving highway speeds in the Mountains outside of Denver on hot days. Would have high RMP's too. But the Tran cooler fixed that right up. My issue now is generic around town driving.))

Thx Dave-in-Denver

Reply to
dwkerschen
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I could be one of two problems, either the locking converter clutch has failed or the clutch in tranny is worn and slipping. Given your area and terrain (I have been in denver area many times) and the fact that you over heated tranny twice, I tend to thnk it is a tranny clutch issue and it will only get worse with time. When you cooked it it may have damaged the clutches and though you have a aux cooler on it now the damage may have been done. Sorry to be a bit gloomy about it.

----------------- TheSnoMan.com

Reply to
SnoMan

Thanks SnoMan, Is this at the need-to-fix pont or can I drive untill it gets worse?

Presuem when I get it fixed I should do the entire tranny and not just the cluch parts... so if that is true I could drive this thing untl I start having real problems rather than just occasional high RPM's on hills.

Will any additives help me with my procastination?

THX!

Dave-in-Denver

Reply to
dwkerschen

THis is a tuff question to answer accurately because there are a lot of varibles here. You can drive it for a while but you should consider down shifting on long hard pulls to easy strain on drive clutch (if this is the problem) and lower tranny temps a bit. If you nurse it it may run some time. If you have oversized tires on it, go back to stock as this will ease tranny strain noticably. If I did a rebuild, I would do a complete overhaul because the parts are not the expensive and the biggest part of overhaul price is labors anf the difference between a partical and complete rebuild is small.

WHen you look for a long term solution, consider this, back in the

70's and earlier Detriot used to gear truck differently for sales in mountain states because of thinner air and longer climbs. They stopped doing it when federal emissions and MPG rating came on board. "If" you plan to keep truck for a long time nad you run bigger tires you would do well to consider regearing the truck as it will reduce tranny strain. (it would extend life of old one the same as small tires would). Myself, I am consideing moving to CO for earlier retirement in about 5 years and when I do I am going to regear my trucks. I have a stock 89 1500 4x4 burb that I bought new that has been in CO many times all aver state and up pikes peak a few times too. It has 3.73's gears with stock tires and it does fine at lower altitudes but above 8000 feet or so it really get weak and OD about worthless. The burb is still cherry and if I take it there it will have 4.10's in it or deeper still if I put bigger tires on it.

On additives, I would change the fluid and filter and keep it fresh and keep a eye on it. As long as it has the funny kinda sweet smell you are okay but if it starts to stink or smell like burnt peanut butter the end is near. Also if it starts to get brownish red or darker still it is not a good sign either.

----------------- TheSnoMan.com

Reply to
SnoMan

Hello! On a different but similar note ~ any issues with replacing fluid with synthetics? So many choices out there these days. Bill

Reply to
me

I thought of that but given that it has been cooked some I am reluctant to suggest a change to its diet as it could go either way with SYN (better or worse)

----------------- TheSnoMan.com

Reply to
SnoMan

Thanks again SnoMan,

GOOD tips on having the entire trany re-done Vs. just misc unhappy parts, etc.

I run 235/75/15 tires... I got rid of the big stock-size 31x10.5 soon after I bought SR5 4Runner years go because I needed the torque with the gutless 2Gen 4Runner 3.0L up here in Denver where the air is thin and hills are steep. Performed much better and got better mileage too. I am do for a new set of tires... have been thinking I would go down a notch to the "standard small" size of 225/75/15 for this SUV... will definitely do so with your advice. THX.

I do not know the gear ratio info... will check out this option too.

FYI... because this SUV has "a history" with it trany temp light I have been extra cautious on trany maintenance. I have had the trany serviced 4 times in 8 years. (2 power flush, 2 filter/fluid jobs).

Thx Dave-in-Denver

Reply to
dwkerschen

You live in beautiful country but as you know it can be hard on trannys. One more thing to remember here. When pulling hard you want to try to keep rpm at and above 2600 RPM. THe reason for this is that you want to get well clear of converter stall area to because when it is in stall area or near it it makes extra heat. Sure a torque converter does boost torque at lower RPM on tranny input shaft but it also makes heat too while doing it and this is why you have had issues with it in past. BTW 225 would be a stepp in right direction and you might even consider 215's too. (it would be cheaper than a gear swap)

----------------- TheSnoMan.com

Reply to
SnoMan

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