Bigscottiedog

Hi folks, long time lurker first time poster. My 91 has 4.11 rear. Getting ready for a new trans, and I see lots of folks switching to A518 trans. I think I can handle the crossmember and od issues, just wonder if it's worth the extra money and trouble. I drive mostly in the city with pretty heavy loads (utility body and a ton of tools). I get around 15 mpg in town and 19.5 on the highway. What kind of difference do you think the swap would make?

Thanks

Scott

jimbo486

You'll definitely want and like having the OD gear the a518 offers with the 4.10s out back as opposed to the 3-speed TF727.

The_Head

A 727 with 4.10's would totally suck

Onemoparnut

What size tires are you running?

Bigscottiedog

2wd, stock everything.

wannadiesel

If you have a '91 with 4.11's and an automatic, you have a 518 already.

Onemoparnut

Unless someone swapped that 4.11 rear in there. Does it have a button to the right of the steering column on the dash that says od?

Bigscottiedog

nope, previous owner put in 4.11

wannadiesel

Ewwww. So top speed is around 60?

Bigscottiedog

well 75 if I floor it. In the city it actually works out pretty good for me. Highway, not so much.

Onemoparnut

What govenor spring do you have in the pump? 75mph with stock tires and 4.11 with no od would be 3500 rpm. That also does not account for any converter slippage so the actual rpm would be a little higher? Do you have a tach in the truck? my truck would only go 60 or so when it was stock with out od and it has 3.55's.

JQmile

Are you sure it has 4.11's? My 89 got 19mpg with a 727 and topped out at 75mph.....with 3.07 gears....how tall are your tires?

Bigscottiedog

ya know, i've always just taken his word for it. It sure does seem to run at high rpm on the highway so I just assumed he was correct about the gear ratio. Guess I'd better jack it up, turn the tire and count revolutions.

JustRamIt91

Go bigger on the tires

Bigscottiedog

thanks folks. Just gonna stick with the 727.