Well I'm keeping my T19 and tossing in 3.10's

[mankypro]

After long deliberations I've decided to run the recently rebuilt T19 thats already in the truck with 3.10 gears and put in a limited slip diff front and back. Figure I'll be in direct drive instead of OD which should save an ounce or two of fuel here and there.

Based on the calcs I've done with 235/85- 16's I figure my RPMs should be somewhere around 2500 at 75mph. Can I ask one of your gurus to check my math?

 

[tonkadoctor]

3.10 Ratio
31" tire height
75 MPH
1:1 4th gear ratio

2520 RPM

 

[mankypro]

Thank you sir.

 

[tonkadoctor]

Yer welcome. Have you had a chance to put her to work yet or are you still getting her patched up and ready to haul.

 

[mankypro]

Still had some slop in the steering so she's sitting at the mech's awaiting a steering column part worth like $80.00 - some sort of sleeve.

After I get back in about a week I'm going to take 'er out on the interstate and open 'er up - see how she does.

 

[tonkadoctor]

I swapped the 4.10 for 3.08 gears in my '90 when I had it. It had the same size tires but a 7.3 w/ZF 5 speed.

Reverse was a bit fast and wanted to hop a little slipping the clutch to get started, pulled OK in 4th, had to use 1st taking off from a stop when empty and took much longer to get up to speed. Might want to compare the gear ratios between the diesel ZF5 and your T19 before you plunk down $$$ for the swap especially if you are towing all the time. It WILL drasticly change the performance of the truck.

I ran around empty most of the time and it did net me almost a 5 MPG increase on the highway at 62 mph. Around town I got about 3 mpg better. Reason I did it was as a fuel milage experiment and a buddy of mine who had a 4x4 shop installed them with FREE labor.

 

[82F100SWB]

Your truck should have a Dana 50 front axle, the tallest ratio available for it is 3.54. You could swap to a D44 carrier to run a 3.07/8 gear ratio, but, I wouldn't personally do that.
Instead, I'd go with 3.54's, and a set of 285/75 or 305/70R16 tires, which work out to 33" tall, and that would put you right around 2500 rpm @ 70 mph

 

[FordGuy100]

Your truck should have a Dana 50 front axle, the tallest ratio available for it is 3.54. You could swap to a D44 carrier to run a 3.07/8 gear ratio, but, I wouldn't personally do that.
Instead, I'd go with 3.54's, and a set of 285/75 or 305/70R16 tires, which work out to 33" tall, and that would put you right around 2500 rpm @ 70 mph

Well if he wants a Dana 44HD, I'll trade him straight up for his Dana 50. Comes with 3.54 gears in it already if you want to go that route. Just a thought....

 

[Mr_Roboto]

With that high of a ratio you are going to have a hard time getting moving in first gear, since the diesel trans also has a high first gear....

High axle ratios should be combined with the use of a smallblock gasser trans which will have the low first gear.

 

[mankypro]

Well the high ratio problem may work itself out if I have a Dana 50 front end - which I won't rightly know for a few days as I don't currently have access to the vehicle. Oh the joys. I really would rather not do the trans I'd be staring down the barrel of another $2500-3000 for that.

 

[Mr_Roboto]

Gasser 4 speeds are a dime a dozen...... The Borg Warners are very durable, I don't see an issue using a used one out of a 1/2 ton truck.

 

[Jake S.]

I would bet that you have a D50 if that is your supercab in your avatar. 99% of them had the 50

 

[mankypro]

So turns out the rear is a 70 and the front I believe was a 50. One shop is telling me that the highest ratio gears I can get are 3.8's, not sure if they're really that accustomed to doing gear work.

I need to crawl under the durned thing and get my axle id's myself.

In any case, now that the tachometer is fixed I took it for a spin tonight briefly and it's at 2,000rpm right about 45-50mph. Not too loud, just the rpms taint good.

So I'll need to get it to a shop that does gear swaps on crawlers all the time and have them figure out if I can get down to 3:10's.

 

[mankypro]

Results the tallest ratio for the truck is 3.75

I have a Dana 70u rear and a 50 front - the weird joint one. I'm screwed. Looks like gear vendors is it. 3.20 final drive for 3k

Well at least I get to keep my t19.

 

[FordGuy100]

Results the tallest ratio for the truck is 3.75

I have a Dana 70u rear and a 50 front - the weird joint one. I'm screwed. Looks like gear vendors is it. 3.20 final drive for 3k

Well at least I get to keep my t19.

3.75 my arce, I have 3.54's in my Dana 70 from the factory. You need to find a new shop if they think the lowest gear ratio that you can get is 3.75.