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Stock gears + Big Tires = Problems with trans?

combatmatt

combatmatt

1/2 ton status
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Alright so this maybe a boner question but its been on my mind for the last few days. Ive got a 91 Blazer running 35's with bone stock axles (3.07 or 3.73, not sure which). Its got a 4L60 (700r4) and the np241. Question is, am i going to burn out my trans by running the big tires without re-gearing? . . . . . . or just be suckin' on gas milage?
 
A friend of mine is running 38s on stock gearing (not sure of his gear either) and a 700r4 and has had the truck back to the trans shop 3 times in 3 months. The truck is only street driven. He has ben running with the od off since the last time and its goin on 3 months now with no trans issues.
 
I look at it this way,if at any point I can switch off O/D on any vehicle im driving and it starts to gain speed then it was lugging the engine IMO,let off the gas some to drop back to where you wanna be and you save gas and engine parts. Pretty much every car/truck made prior to O/D trannies ran a 1 to 1 final ratio in top gear and were fine for years of service,Ive also been running my 84 without OD since I got it.
 
goofy1 said:
A friend of mine is running 38s on stock gearing (not sure of his gear either) and a 700r4 and has had the truck back to the trans shop 3 times in 3 months. The truck is only street driven. He has ben running with the od off since the last time and its goin on 3 months now with no trans issues.
Click to expand...

I have stock 3.08 gears and 35" tires. This is a recent purchase, so I didn't do that on purpose :D

I've been manually shifting, and using only 1st and 2nd around town with a 700r4. I'm hoping that is much better on the tranny.
 
As long as its not hunting between 3rd and 4th and locking up the torque converter it should be fine. Definately harder on a trans though.
 
not to highjack anyones thread but if I have a shop do the front and read gears what should I be looking to spend?? I dont have a problem working on the motor but transmissions and gears I know nothing about nor do I have the proper tools.
 
when i was gona do gear swap.they wanted 600 per axle.i just got a manual and dial indicator and did it myself.
on the tranny issue and gearing.i would not use overdrive on 3.08 gear ratio and big tires.does not mix.1 to one ratio it is in 3rd gear anyway and with 3.08 and 35 inch tires the final ratio is about the same as your original setup with od.
 
When I bought my k10 it had 3.08's and 39.5/16-15 Baja Claws... it took all of about 6 months to smoke the tranny and I was being easy on it. Granted the trans had unknown miles on it but regardless I wouldn't be surprised to grenade a brand new one with that kind of gearing/tire combo.

Since you're running 35's in my opinion you'd be a lot better off hunting for a set of axles out of a k20 truck/suburban since it'll give you a 14 bolt and a d44/10b but you can find them with 4.10's.

If you want to keep the 10b's because of clearance then spend the money to re-gear but I know for a fact you can do a 3/4 ton swap for under $600 and 4.10's would be perfect with your 35's.
 
guys thanks for the input, youve all confirmed my suspiscions. I needed a good kick in the a$$ to get me up and moving on my d60/14b (4.56's and lockers) rebuild and swap and not wanting to smoke my new trans is probably motivation enough. Now its off to the internet to buy rebuild parts, new tires, new wheels, disk conversion. . . . . . . man it starts to add up don't it? :D
 
Everyone says 4.10s are perfect with 35s, well I did my 3/4 swap and 4.10s on an incline, is jumping back and forth from 3rd to 4th, not an ideal situation at all, actually its quite horrible.
 
hunting on incline

Going up an incline is going to cause the tranny to want to downshift to maintain the given speed. That specific situation is not when everyone is saying that is the perfect gear. Everyone is talking about cruising down the highway at 65-70mph, not climbing hills.
 
But even on a slight incline on the highway or streets it seems to do it. Just seems like there are options that would be better, tho 4.10s are the easiest.
 
transmission hunting

I wonder if a shift kit or reprogramming kit would help, you could call transgo and ask them about one of their kits, or any manufacturer for that matter, i've just heard good things about transgo.
 
combatmatt said:
Alright so this maybe a boner question but its been on my mind for the last few days. Ive got a 91 Blazer running 35's with bone stock axles (3.07 or 3.73, not sure which). Its got a 4L60 (700r4) and the np241. Question is, am i going to burn out my trans by running the big tires without re-gearing? . . . . . . or just be suckin' on gas milage?
Click to expand...

first thing you need to do is get a cooler on that trans asap....
 
Artemis Entreri said:
Everyone says 4.10s are perfect with 35s, well I did my 3/4 swap and 4.10s on an incline, is jumping back and forth from 3rd to 4th, not an ideal situation at all, actually its quite horrible.
Click to expand...
run the tranny in 3rd until the rpms get back up.if its hunting that much,you may already have a problem.from 3.08 gear and 30 inch tires that came stock,you would need to jump up to 4.56 to get a good rpm to stay in od longer.if it is hunting gears that easy on yours you can run it in 3rd and save the tranny as long as rpm is not too high.even in 3rd with 4.10 you shouldnt be over 3000 rpm at 70 mph.
 
Gotta get a tach installed, the problem cleared up tons after I put the right ujoint in the rear, haha. Still does it a little bit, but not nearly as much.
 
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