Gearing Question - 38's and 4.56's...

sredish

sredish

Where am I?
I'm running 4.56's. Haven't had them in but maybe 4,000 miles, although the truck sat for 2 months not long after they were put in. I really am not happy with the gearing, it's just too low for me, even with the 38's. When I bought the gears, I had anticipated maybe 40's but now I realize I don't want the headache of going bigger. I was thinking 4.10's at the most. I also think this may be contributing to my harsh shifting, being geared so low.

I think around 75mph, I'm close to 2400 rpms or so and I'd like to drop that down to 2k. How much harder would 4.10's be on the trans versus 4.56's? I don't really see it being that much harder.

I'd appreciate any comments on this. I was hesitant with the gear choice when I got them and I feel I should have followed my gut.

:thankyou2:
 
I'm running 4.56s and 38s as well.....although I have a 7.3
It's not a bad combo...love the power around town...rpms could be a little lower on the highway. According to some pics I have....at 90mph I'm right about 2700rpms

Dropping to 4.10s may be a little harder on the trans and will give you somewhat higher EGTs.

You could run all the numbers to figure out your rpms at a given speed on the calculators on Randy's Ring and Pinion website to see what difference you'll see with 4.10s, 4.30s, 4.56s, etc..
 
I don't get it... I'm running 4.56 with 40's and have no issues at all with shifting or driveability. I am at 72-73mph at 2000rpms
 
Thanks for the comments guys.... The truck as at the dealer due to a bad aux. fan clutch and a few other warranty particulars, then we'll see how she's running. Per my tech and DJ, the clutch fan code can cause some weird tranny issues, so I'm hoping that'll be rid of the funky shifting.

I'm getting some vibes above 2500 rpms, and it's not the front driveshaft. The rear driveshaft is a High Angle unit and it shouldn't be vibrating, although, I still have the shims in the carrier bearing mount and they wanted me to take them out, so that's next on the list for that issue.

That vibe is another reason I wanted to bring the rpms down, thought maybe the bigger tires and low gearing are causing some excessive vibes, but you guys are happy with them, so I'll see what I can find.

Thanks again.
 
Kevin and I both have the High Angle Driveline two piece driveshaft with the 1350 CV after the carrier bearing.
I run no shims at the carrier bearing and have a 2" tapered block in the rear. No vibrations at all from 0-100+

I say pull the shims out at the carrier bearing.
And are you running flat or tapered blocks?
 
DC, I'm running flat blocks. But, I'm very close to ordering some rear springs. What springs would you suggest to run with the front lift that I have, Fabtech brackets and 4" Deavers. If I did springs, should I also keep enough room for a small tapered block? Main reason for wanting rear springs is to improve ride quality.

I would like to add to the front a little more, like Donahoe hangers, but with the vibes above 2500rpms, I'm feeling that it would get worse, so I'm holding off.
 
I think part of your vibe issues comes from the use of the flat blocks as well. With the CV after the carrier bearing you want to rotate the diff upward so that the pinion is almost straight with the driveshaft at ride height (you want the pinion a few degrees lower than the driveshaft to compensate for rotation on acceleration....Jesse can tell you how many degrees exactly..I forgot LOL ). The tapered blocks I have worked perfectly though.

Remove the shims at the carrier bearing, and switch to tapered blocks and all should be good. That's the combo that Kevin and I run with the same driveshaft and zero vibrations. I'm at 8.5" of lift and Kevin's at 10.5" of lift.

You could go with either 5" or 8" rear Deavers. For the softest ride, the 5" rear Deavers would be the way to go with maybe a 2.5-4" tapered block (depending on if you want any rake at all....and if you go to the bigger DR hangers in the front)...



Hope this helps.
 
awesome DC, thanks for the info from both of you. I talked to Kevin at TT earlier today we both decided on a set of 5" Deavers as you mentioned then the proper block for the application. He said it'd ride real gooood! So, that's what I'm going to go for. Truck should be out Monday and I have a long laundry list of stuff to finish up...

* Swap out multi-channel amp
* Install gauges
* Mount and wire Amp Powersteps
* Dynamat front doors
* Swap out winch cable with braided rope
* Mount truck box
* Install and wire navigation box
* Swap out muffler with a new one (this one got crushed off-roading)

I'll also have to see how the trans shifts after getting the current probs fixed and resetting everything. I'll have to add the rear spring setup in there as well.

Thanks again for the help, I'll let you all know how the trans works when it gets out Monday.
 
Yep, I'm told dearched 5" Deavers with good shocks gives a very, very soft ride. I'm tempted to get the 5" rears for that very reason....
Kevin and Marty at Truck Toyz are great people to deal with :rockwoot:


Sounds like you'll be busy once you get the truck back....nice :)

Yeah, let us know how the shifting is once you get the truck back.
 
I agree with Marty and Kevin. They were both very patient with me asking a thousand questions before I bought my lift
 
Yep very patient and knowledgeable guys. Marty has given me a ton of info and taught me a lot over the years.
 
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