Is it worth regearing from 3.54 to 4.10?

[351FUN]

The truck in question has a blueprint 306 with 377hp/362#ft and I'm about to downsize from the 37" humvee tires to 35" BFG's.  I was already on the fence about what gears to do between 4.56 and 4.10, but with the smaller tires 4.56 seems like complete overkill.  Going from 3.54 to 4.10 is only a 14% difference, so is it even noticeable in daily driving?  It'd get the speedometer back to about stock iirc.  

The axle code is 33 and it's a 1983 F250.  It never sees highway use and I don't even want to think about it getting about 75mph.

[351FUN]

Also I have the 4 speed manual T18/19 I can never remember which one.

[ArdWrknTrk]

14% more torque may be worth it.
I don't know how strong your engine is.
Pretty sure the T-19 were only installed behind 460's and 6.9 diesels.
A T-18 does not have a second PTO cover on the left (driver's) side like the T-19 does.

[Gary Lewis]

You should have a T-18 as the T-19's came on the 460's and diesels and won't bolt up to a smallblock.

Big Blue, with a 460/T-19/3.55/33" tire combo started OK from a stop in 2nd.  But by swapping only the tranny to a ZF5 things are just a bit too "tall" for easy 2nd gear starts.  I still do it, but have to rev the engine just a bit.  And that was changing from a 3.03:1 2nd gear to a 2.94:1.

When I put the D60 in front I was faced with either re-gearing it from 4.10 to 3.54 or changing the rear from 3.55 to 4.10.  In hind sight I wish I'd gone with the 4.10's as it would have made 2nd gear starts much easier and the increase in R's on the highway probably wouldn't have made a lot of difference - it is a 460 and gets poor MPG anyway.

So, were I you, I'd play with the calculator at Documentation/Driveline/Calculator and see what you think.  You can see the gear ratios for the transmissions and play with rear axle ratios to your heart's content.

[351FUN]

@ArdWrknTrk I put the HP and TQ in the post, is that what you're referring to about the engine or is there something else needed?

Gary, I've played with that for a while already and with the tires right now I have to rev higher and slip more than I like in 2nd, so first is usually to get going gear still.  The Humvee surplus tires are extremely heavy though, so I'm definitely going to wait until I have the new tires to make any final decisions.

[ArdWrknTrk]

I should have said 'how strong, you feel your engine is'

I have 4.10's and a 460 with stock size tires.
You seem to get by with 37's and a 351, so I'm not the one to be giving advice about gearing

[351FUN]

I gotcha.  Yeah I'd like it to be quicker of course, but it's already faster than it needs to be.  

[FuzzFace2]

Gary Lewis wrote

You should have a T-18 as the T-19's came on the 460's and diesels and won't bolt up to a small block.

So, were I you, I'd play with the calculator at Documentation/Drive line/Calculator and see what you think.  You can see the gear ratios for the transmissions and play with rear axle ratios to your heart's content.

Gary the T18 / T19 / NP435 have a removable bell housing unlike the ZF or M5OD transmissions.
So if the input shafts are the same, they are for the T18 & NP435, the T19 could have been swapped in.
Dave ----

[grumpin]

My Bronco and my truck have 3.55’s. The four trucks I owned before these two were all 4.10’s.

I really like the 3.55’s over the 4.10’s. Less rpms and both motors have plenty of torque.

Drove the Bronco today on about a 400 mile round trip, with the E4OD at 70 MPH, IIRC, I was turning 2100 rpm.

I quit doing second gear starts unless I really had to get going, easier on the clutch IMHO.

[ArdWrknTrk]

But Dane, do you have really heavy 37" tires?  

4.10's would definitely help get that truck moving.

[grumpin]

ArdWrknTrk wrote

But Dane, do you have really heavy 37" tires?  

4.10's would definitely help get that truck moving.

No, and that’s just my perspective.