Rear End Questions

[tjg_26]

Alright boys im going to have to end up changing the gears in my 71' truck's rear end. first of all its a 71' half ton truck, with a four speed with granny's gear. It has a 302 and is all stock exept for the rebuilt motor. I dont know what tranny she has, but I cannot find out right now. It tops out at 65-70, which is why I need to change it. I am thinking about going to an automatic, but havent made it that far. This will be my daily driver, so I need more speed and some good gas milage . The most I pull is a snowmobile, but maybe a car out of a ditch once a year . Everything Is stock, so I would appreciate if sombody could tell me what the tranny is, and how much the gears will set me back.

Thanks in advance,

Tyler

[flyboy2610]

When you shift it into reverse, is the lever up or down?

[ToughOldFord]

Tach out @ 65-70?! That sounds like a 4:56 rear, but I didn't think they'd put that in a half ton?

[tjg_26]

thanks for the replys, reverse its at the top right. yes, I guess, a 302 should go faster than 70! so Please if you can find what tranny im running with, and whats a good gear ratio I should go to. Keep in mined, Im trying to not to have high rpms for good gas milage . I appreciate the replys...

THANKS FOR CARING,

Tyler

[theskytoucher]

Well the tranny sounds like a t-18 to me.
In my truck i have 3.25 in the rear end and run about 80 at 4000 rpm.

[flyboy2610]

Yup, you have a T-18

[69rangerman]

I've got a 69 302 with fmx auto and 3.25 rear. Before the motor quit last week (tearing down now for rebuild) I'd managed to get 15 mpg. Once I get the motor back, I anticipate 16-18 once it's broken in. She'd easily hit 80.

You might want to think about swapping in an 80's AOD for mileage or maybe a four speed manual.

Good luck

[tjg_26]

THANKS ALOT GUYS!

How much work (and cost) does a project like this take?

Thanks,

Tyler

[foghorn]

just swap to a 3.00 pumkin it's easy to do and only cost me 100.00 plus lube and gasket and seal

foggy

[fitzdicksn]

There is a good chance he has a Dana 60 rear axle with about a 4:10 ratio. I have a 1969 Ford F100 Explorer long box 2WD with a 240 I-6, 4 spd floor shift with the granny low backed up with a Dana 60 with a limited slip and a 4:10 ratio and 5 bolt wheels. It gets about 10 mpg(US) at 60 mph and it tops out at around 70-75 mph. It also came equipped with Heavy Duty suspension and was made in Oakville, Ontario if I recall correctly. Our family bought this truck new in 1969.

I have seen several other F100 and F150's with the same rear end as new as a 1979 in the wrecking yard that I am going back to get. From what I have seen looking under thousands of F100's they are very uncommon. They also apparently were available in the 64-66's.

[Clarko]

It's possible. 67-69 F100s with HD suspension or 4x4 had a semi-floating 60 http://77cj.littlekeylime.com/Spicer/gr ... ating_.gif

[ToughOldFord]

But a 4:10 shouldn't wind out @ 70mph, my 69 had 4:10s and it did an easy 80. Might have even had more, I just didn't dare take the old thing any faster.

[Big D's 69]

I know for sure a 4.10 with an auto will trap over a 100 mph through the 1/4 mile.

[Clarko]

How tall are the rear tires? That will affect the top speed a lot.

[tjg_26]

Ok Everybody, thanks for everything. I noticed when I let the thing idle for a little bit, I had a dribble. Yes, it was gasoline. I got that fixed right away, but haven't had a chance to see what she tops out at. Well, I will post updates when I get that information. Thanks for the great information, answers to the questions follow.




Thank you,
Tyler