Is it worth changing gears for better MPG's???

[DA BIG ONE]

After all is said and done I admit I would have saved $$$$.+ dollars not changing out gears on my 4x4 burb to 3.42's from 4.10's.

Been through 2 sets of GoodYear MTR's stock and 285's great of road but a waste on road. Now using 285 GoodYears SilentArmor like the quiet sure footed ride on road and they work good in sand.

MPG is not consistant unless I drive at slower speeds, but I'm now geared for 70+ mph and the drag is a drag.........................

I'm actually thinking seriously about going back to 4.10's maybe 4.58's w/taller tires................

[rjwest]

I doubt your TCC is ever locked...

[DA BIG ONE]

Been mulling this around for some time now and decided to go back to the 4.10's.

Will have the 3.42's on the market soon, frt 9.25" ring w/pinion, rear 10.5" ring w/pinion.............

[rjwest]

try the resister to fool the tcc lock up, stay in 3rd gear, tcc should stay locked above 45 mph, don't use 4th on a hill, down shift manuel...

2nd gear will also lock tcc about 32 mph...
but you have to shift manuelly, as Trans will be in high pressure mode,


Need to shift like it's a std shift, un-throttle and match rpm to drivetrain.

I installed a sw for the TCC lock up, and a sw for the 3-4 shift,
2 sw's by the console to control shifting...

[DA BIG ONE]

try the resister to fool the tcc lock up, stay in 3rd gear, tcc should stay locked above 45 mph, don't use 4th on a hill, down shift manuel...

2nd gear will also lock tcc about 32 mph...
but you have to shift manuelly, as Trans will be in high pressure mode,


Need to shift like it's a std shift, un-throttle and match rpm to drivetrain.

I installed a sw for the TCC lock up, and a sw for the 3-4 shift,
2 sw's by the console to control shifting...

I'd like to try this, what's involved?

[rjwest]

50 ohm resister accross the tran emp sensor to ground, through a switch.
this will allow the TCC to lock up at 40 mph for a 3.73 gears,
allow 2nd to lock the tcc at 28 mph for 3.73 gears.
4th , mph not affected,(abot 50 mph tcc lock up)
But the TCC will not unlock, will hold untill down shift , ( very harsh shift ) thats why you need to manually shift,,,
Note all all your speeds will be about 10 per cent higher, with the 3.56
( there are posts on the resister. ).....




for the 3-4 gear shift, need a switch in one of the 3 shift control lines,
that go to the trans,leave in 4th, open switch and it will downshift to 3, close for upshift.

I will have to look in my manuel to find which wire it is, will get back to you,
Note: if you forget and leave in 4th lock out ( 3rd gear, sw open )
and restart engine, a code sets that makes a harsh shift,,,

I was working on a 2-3-4 shift box, with a lock out relay, to prevent
the code problem but sold the truck.

If you have a code reader, setting code is not a problem as a code clear resets it.


will get back with more info..

[Shikaroka]

I have read most (if not all) of this thread, but I am still a bit confused.
I just swapped out my 4.10s in the Burb for some 3.73s. I rarely tow and never very heavy. I was looking for some lower revs on the interstate and my rear end needed rebuilt anyways.
I checked my speed with a handheld GPS and it appears as though I am actually going about 3-5 mph faster then my speedo claims.
Do I need to "Hack the VSSB"? Or, maybe get a signal modifyer to hack the VSS? I'd like to have my speedo be more accurate and I'd like to have the TC lockup a little sooner (for economy if possible). What should I do? What's the best compramise?
Any advice/help would be appreciated.

Thanks!!

[JohnC]

Hacking the VSSB can correct the speedometer. The TCC lockup is based on engine speed (torque) not road speed. No easy way to hack it and it probably isn't a great idea. If you did hack it you'd want it to lock up earlier only under very light load conditions, which may result in it going in and out of lock annoyingly often...

[Shikaroka]

See? I am confused.

So, is hacking the VSSB the best (maybe easiest/cheapest) route?

[turbotim]

I'm new here and tried to read through this thread before asking...I recently picked up a "95 3500 HD 2WD dually w/19.5s that has a 4L80 and a Dana 80 rear diff. that according to the tag it is 4.63 and noticed everyone else seems to have 3.42,3.73,or 4.10. It needs a rebuilt 6.5L and wasn't running when I bought it, so I have no idea how it is at highway speed or the mileage. I'm in the process of building a dump bed for it, and it won't see speeds above 55mph very often and will be used to tow on occasion. Does this sound like the correct ratio for this truck and it's intended use? I apologize if this is a dumb question, but I'm new to all of this... /// tim

[mr. monte]

for that diameter tire, sounds right

[JohnC]

Hacking the VSSB is the way to correct the speedometer. The TCC lockup speed is best left alone.

[93GMCSierra]

just a couple of questions, I have a 5 sp manual trans the shifter was labeled
L 1 2 3 OD
However I can drive in OD at 23 mph with out lugging an even have some torque on acceleration an at 65 mph my tach is about 26-2700 RPM. When really pushing the truck I hit 90 mph at 4000 which is were it seems to have a rev limiter, which is good as I was not intending to blow the motor.
Now my questions are this, why do my RPM's seem alot higher then others with the same set up?
Oh an when I got the truck it had stock sized tires, 245/75/16 steel rims, now has 265/75/16's still steel rims.
My speedo has not been corrected however the difference between its mark an a traffic radar checker is at most 2 mph at 45 mph

[TurboDiverArt]

just a couple of questions, I have a 5 sp manual trans the shifter was labeled
L 1 2 3 OD
However I can drive in OD at 23 mph with out lugging an even have some torque on acceleration an at 65 mph my tach is about 26-2700 RPM. When really pushing the truck I hit 90 mph at 4000 which is were it seems to have a rev limiter, which is good as I was not intending to blow the motor.
Now my questions are this, why do my RPM's seem alot higher then others with the same set up?
Oh an when I got the truck it had stock sized tires, 245/75/16 steel rims, now has 265/75/16's still steel rims.
My speedo has not been corrected however the difference between its mark an a traffic radar checker is at most 2 mph at 45 mph

What kind of gears do you have in the rear? It's either steep gears or your tach is off. 4000 RPM's seems pretty high. My engine has pretty much quit at 3500.

Art.

[93GMCSierra]

What kind of gears do you have in the rear? It's either steep gears or your tach is off. 4000 RPM's seems pretty high. My engine has pretty much quit at 3500.

Art.

I have not had the opportunity to find out yet, nor which transmission it is. Or is there only 1 5 spd they put in these trucks?

[JohnC]

There was only one trans in '93 for the 6.5. Don't know if the 6.2 was the same or not. Chances are your alternator was swaped and has the wrong pulley. This throws the tach off. 4000 RPM is above the governor set point.

[93GMCSierra]

Has anyone ever replaced the stock 5 spd with a 6 spd?

[6.5 Detroit Diesel]

I know a few people who have swapped the trannys. The Dodge trucks have the NV5600's which is the 6-speed. I think one of the biggest things would be finding out if the bellhousing from the 4500 will bolt onto the 5600.