rrt898

I have a 1986 coupe with a Dana 36 and a 2.59 rear. Last year I had a rear rebuilt with a 3.54 ratio. I never installed it because I think its too much gear for a mostly stock 86. I purchased my 3.54 from Tom's Differentials, which is US Gears. Tom's doesn't have a 3.07 for my Dana 36. He only has a 3.54 or 3.73.

What is a good brand to purchase a 3.07 from??

WVZR-1

I believe I'd try for an assembled OEM take out first! You package assembled should be an easy sell I'd think.

UNCLEBILL

I would not worry about too much gear. I have a 1990 Vert and went from 2.73 to 3.54 gearing and its just right. I thought like you it may be too much but it is not.
Note...Im retired and like it
Bill

rrt898

I know around town it would be good. I was concerned with the highway. I didn't want the car screaming at 60mph. I don't care about fuel economy. How is your car at highway speeds (65-75)?

thanks...

UNCLEBILL

I had it documented but it was a few years aqgo. Memory ...60 mph about 200 rpm more.....1750 rpm to just under 2000 rpm......75 mph about 350 more rpm than stock. That compares 2:73 vs 3:54 gears. Did not feel it was screaming. I baby it but like to get on it every so often and when I did didnt feel any difference in sound just quicker.Hope that helps.
Bill

ucfsaxman

It certainly helps me I'm considering going to 3:54's and was concerned that it would be too much of a sacrifice for my daily driving duties but this is good to hear.

rrt898

When you installed the rear, did you have to align the rear? I thought I saw a post on "how to without an alignment" I am probably going to give the 3.54 a try. I have been looking at for over a year.

thanks..

UNCLEBILL

No; did not have to realign but had to replace the drive and driven plastic gears on tailshaft for speedo. The tough part to find is the VSS. The VSS for 2:59 and 2:73 have a common VSS for the driven plastic gear of 34-39 teeth. You will need a VSS from a 3:07 setup as this accepts 40-45 tooth driven gear. The 3:54 is a 43 tooth so this is okay. You will have to find a used VSS off a 3:07 as I did as they are not sold anymore just the VSS you have now at present...go figure!!!! The VSS has the tooth range stamped in the part so you can be sure of what you find. I had the speedo checked by GPS and it is accurate. The gas mileage drops about 1-1-1/2 mpg but mine is not a daily driver just my retirement fun toy. Could be how I drive?
Hope this helps.
Bill

rrt898

Thanks again for all the help. When I rebuilt the trans I installed the correct drive and driven gears for the 3.54. So for almost two years the speedo has been off (almost 10mph at highway speeds). I think you convinced me to install the new rear. My mpg dropped with my stall converter so, I will probably loose a little more mpg. My car is a good weather driver also.

Thanks again for all the help

aboatguy

Is your stall converter a locking one? I didn't notice a drop in mileage with any of my converter changes. I started with stock went to a 2800 midwest and finally to 3500 vig. (I broke the midwest) I did notice a slight change when I went from 2.59 to 3.45 and a bigger change from stock engine to ported heads, big lumpy cam, etc.


back on topic if the converter is locking and locking early during part throttle operation, the mileage hit from a higher than stock converter should be minimal in town and zip nada zero, on the highway.
Mike

rrt898

Its a locking converter but; I have it on a switch because it locks up way too early for me. I usually only lock it up if I am on the highway. Its my driving style, not the car for the loss of mpg.

aboatguy

OK your manually locking it so that makes sense. I know all about performance induced mileage loss. Seems like my grin gets bigger when instant mileage is in low single digits.


Mike

aboatguy

Lower numerically gearing is good, the 2.59s are only installed in C4s to make CAFE standards. I have 3.45s and 2k is a little above 70mph.

If your just changing the pumpkin you should be ok without a new alignment. However , I always err on the side of caution since F1 GSD3s are so freaking expensive.

Mike