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Steve, this may be a bit off subject but you seem to know about this stuff... or, frankly, anyone else can answer this also... about how expensive and difficult would it be to swap the rear differential in my truck? There were two axle ratios that year and mine has the lower ratio that makes the engine spin faster at speed. One would think it would save on gas and engine wear if I had the other ratio, but if I have to spend a thousand bucks just to get ten more miles on every tank of gas, it wouldn't be worth it.
If that's not feasible, can the transmissions be rebuilt with different gear ratios so that the engine runs at different speeds for different vehicle speeds? If that can be done, is it advisable?
Probably the most practical way would be to find the higher-geared axle in a junkyard. You could put new brakes on it, then install. On most trucks, R&R of the rear axle is not that tough. A floor jack and a rattle gun would help, as would putting some good penetrating oil like Kroil or PB Blaster on the bolts/nuts you will be removing say a week before you do the deed.
You could of course just change out the ring and pinion, but for most shade tree types, doing the whole axle is easier. And you may find someone who wants to buy the lower-geared one, if you are inclined to sell it and recover some of your money.
Do the math, find out how much better MPG the higher gear will give you, you might be surprised how quickly you would save a grand's worth of gas.
Frankly, I'd like to install a manual transmission if my automatic ever dies. Any of y'all know how easy that would be?
Wouldn't even bother. You certainly could source parts from a manual trans model, but it's not worth it.
Quote:
Originally Posted by RomaniGypsy
Steve, this may be a bit off subject but you seem to know about this stuff... or, frankly, anyone else can answer this also... about how expensive and difficult would it be to swap the rear differential in my truck? There were two axle ratios that year and mine has the lower ratio that makes the engine spin faster at speed. One would think it would save on gas and engine wear if I had the other ratio, but if I have to spend a thousand bucks just to get ten more miles on every tank of gas, it wouldn't be worth it.
If that's not feasible, can the transmissions be rebuilt with different gear ratios so that the engine runs at different speeds for different vehicle speeds? If that can be done, is it advisable?
The flip side of swapping from 4.10s to 3.73s is that now you're engine is spinning 10% slower and you now need to gas it a bit more to get going from a stop. Net gain = not much, really. I'm sure I could swap down to 3.08 from 3.55 on my truck, but I'm not going to pretend that having to punch it from ~1200 RPMs (now about 1400 RPMs) to pass someone will do anything but waste gas.
Keep in mind that you've got a really heavy truck and even a diesel needs revs (to a certain point) to push that brick on wheels around.
My dealer-owning friend drove a 98 K3500 X-cab dually around before he sold it of. It had a manual trans and got 14 MPGs no matter what. That was before ULSD.
As for rebuilding with a different gearset, that depends if anyone offers that for a 4L80E. I've heard of F-body swaps to that trans, but I don't recall innards being swapped along as well.
You can find rebuilt 4L80E's for $1600 or so. Then you have the cost of removal and install. so you looking around 2500-3000 depending on shop rate.
I don't know who told you that you have to remove the transmission to change the starter but they were blowing smoke up your a$$.
There is a bracket on the front of the starter that is a bugger to get to but other than that it is a straight forward job.
This. I did the starter replacement myself on my '94 Chevy 6.5 turbo diesel dually and it was easy. The starter was only $85 and it took about a half hour to do. Hardest part was getting the front bracket on and even that wasn't too bad.
Something to think about would be to try some taller tires next time you need tires, you could thus "try out" some taller gearing, and see if it works for you. I think this truck has the reprogrammable speedo so you can get it recalibrated to be correct.
If GM offered a 3.73 gear as a factory option, it probably works well for some users. You wouldn't want to go to a 3.08, of course, assuming you could find one, but probably if you mostly drive on the open road, and don't usually haul heavy loads, the 3.73 might actually work better for you. Kind of hard to tell without driving the truck myself, or ride with you, and even then it's hard.
See if you can find a truck with the 3.73, maybe one at a dealer for sale, go for a test ride, maybe.
Not too sure I'll be looking to do that, given that I'm eyeing a travel trailer or 5th wheel to pull with the truck. I'll probably need the 4.10s for that. However, I just figured I might get better gas mileage with different gearing... if I could have a good pulling ratio in 3rd gear and then have 4th gear be super-high for low-RPM cruising, like 1600 rpm @ 70 mph, that'd be amazing.
From the first time I test-drove this truck, it just felt like it didn't want to go over 60 mph. I've had it up to 85 but there has always been a noticeably increased need for throttle beyond 60. I get 25 mpg @ 55 mph, 19 @ 62 mph, and 15.5 @ 70 mph. I can't help but think it has something to do with the gearing, given how the optimal torque from a diesel comes at lower RPM. I know that my truck has the aerodynamics of an oversized Kleenex box, but it seems so odd that the gas mileage would vary that much. After all, it drops by almost 40% from 55 mph to 70 mph... that's weird. I had a 1972 Cadillac that wasn't exactly aerodynamic, and it had that 3-speed TH400 slopbox transmission... but it'd do 15 mpg @ 55 mph and 12.5 mpg @ 70 mph. That's a 17% drop. I can see that. But an almost 40% drop?
I'm just thinking about these things for when I get the transmission redone. The truck has 207,000 miles but the engine has only 132,000. It was used mostly to pull an RV for its first 146,000 miles and although the transmission has given me absolutely zero trouble in the 61,000 miles I've put on the truck, I don't imagine it'll last forever. I'm intending to go on the road with my wife to tour around as musicians, part-time if not full-time, and we're probably going to use my truck as the touring rig at least for a while... because it's what we have, and I know what condition it's in from having owned it for almost four years. Considering this stuff for the future might be beneficial.
I've got a 1994 chevrolet 6.5 diesel 2wd with the 4L80-E transmission in it. The transmission is in great shape still. I'm wanting to sell transmission but with it coming out of a diesel would the transmission bolt up to a gas burner
Whatever you're putting it into will need to have a controller(computer) as that transmission is electronically controlled.
You CAN make a manual shift for it (using switches as simple as household light switches), but the one/two shift is incredibly harsh, as there is no way to control line pressure without the computer.
There are stand alone controllers available (cheapest around $550.00), but you'll still need to add other "electronic friendly" bits to get things like the speedometer to work.
Probably the reason for getting that many miles on Your transmission is, the fact that the vehicle has those 4:10 gears.
As stated,with taller gearing, 10% fewer RPMs, 10% more throttle and, 10% more load on the transmission.
Figure that 10% with the loads You will be pulling and, well, I guess it would be at least, if not more than, 10% more heat and wear on the internals of the transmixer.
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