5-speed trans conversion

I have a Ford "top loader" four speed trans with an overdrive. That gives me 8 forward gears not counting the T/C options. I find I use the O/D as a splitter a great deal. But I am never at a loss for the right gear. Herm has the same setup in his own Jeep.

 

To me, Turbos + offroad = breakage. From experience 1999 Ford F-250 turbo diesel (single cab short box). When your approaching an obstical you start making it up that hill and all of a sudden your turbo kicks in when you don't want it. Two things have happened to me. A Roll over, the other was a twisted driveshaft. The f250 isnt my offroader anymore... Turbos are fun on-road though

 

Well, maybe apples to oranges, but I don't see how that's physically possible. Any boost means that you are adding more fuel per charge. Basically the turbo does the same thing as increasing the displacement - bigger charge means more power. I thought that the main reason for turbos in passenger cars was as a dodge around insurance and/or displacement regulations . This is also why the boost does not cut in until the revs are up: otherwise, you are consuming much more fuel for normal driving.

The main complaints I've heard against turbos in Jeeps have been 1) higher complexity with more stuff to wear out, and 2) sensitivity to dirt.

 

Well I did mention going easy with the go peddle.
However with all that extra available horsepower keeping your foot from mashing that peddle down would be extremely difficult.

Looking over Herm's selection that 4speed overdrive Ford transmission would be the way to go.
If it will fit your application. Money wise it would be an even up toss between that and the new overdrive to go behind the D18 and T90. (For me I mean) The over drive would be easier to install.
:hurrican:

 

Your plan to turbo a 225 caught my eye. I have a t86 and a overdrive (Saturn/Warn). I doubt your will miss the extra gears of the five speed unless you plan to run it on the drag strip. Our jeeps are so light that you will not build much boost in first gear(no load). I can easily get 15 lbs. of boost in 2 and 3. If your jeep has 3.73 gearing, you can cruise at about 1700 rpm 65 mph (30 inch tall tires) in 3rd OD. You can also build boost in 3rd OD easily. I believe my shop manual says turbo 231 compression 8:1 I run the highest octane pump gas I can find to avoid the dreaded knock or preignition. Stock bost for 231 85 vintage was 5 lbs. My jeep does not boost unless you step into the throttle and put the engine under load. My gas milage is about 10 to 12 mpg. I will admit that I love to wind up the turbo so that probably has a lot to do with the mpg. I have a stock setting for the computer that will probably get 15 mpg but I can't convince myself to run it at the stock setting for any length of time. I can not give much advice about offroading this Jeep. I have had 225 powered jeeps for over 20 years and done mild wheeling. I need to mount a cage before taking this one on any trails. Iif you are creeping in low, you should not load the engine and build boost. AM

 

A mandery is right on the compression ratio, naturally aspirated 231's had 8-1. I checked my 1980 Chev Monza Factory Service Manual last night and that's what it listed. Didn't have any specs for the turbo version though.

 

I figured that i had the turbo setup, and if it didn't work, i wasn't out anything. I'll have to draw a schematic of the idea, because it is a draw thru style system, meaning that the carb sets before the turbo, so the air and fuel are both compressed before entering the manifold. The turbo books from Gator Turbos has helped alot in the design prossece, unfortunatly, it won't be known how well it works until spring/summer, as the frame is still being assembled, and i need a body first so i can plan where the exhaust tubing will end up.
From the research i have done, the draw thru is best because you can have as much or as little boost as you want, because you don't have to seal the carb.
I'll try and get a schematic done tonight and get up tomorrow, monday at the latest.
Thanks for all the information
Matthew Haver

 

Ya mean you aren't going to strap a seat to the frame rail and go for a ride?
Which is, come to think of it, easier with the through the floor peddle setup.

 

So adding a gear (transmission) will give you less RPMs and theoretically better MPG? What about gearing (rearend)? To put it ignorantly, does the rear differential just spin faster and not restrict the transmission?

 

Sparky,

Forgive me... I guess my synapses are a little slow! When you say "higher" do you mean something with a lower numeric value (like 3.54 or 3.08), as opposed to 4.10 or up? :?

 

"Higher" usually means a lower numeric value, but it is confusing. I take it to mean lower numeric, since lower (higher numeric) gears are considered superior for off-road use.

<edit> I should have known - Sparky is always around. No need for me to answer!

 

Tim,
You and Sparky have always provided good info as far as I am concerned. I can quietly read and learn how to fix my Jeep! That's pretty dang good, IMO. But, you made me smile with your reply. However, I had to ask my wife... I was higher when I should have been lower! R)

 

Yeah you do. You make webpages I use in class to answer questions.

 

Probibly could, but doubt it will be done in time before it snows. heck, mother nature is already taunting us with sleet and rain/snow mix.
Sorry, no pictures yet, couldn't get the camera to work right. But as the jeep progresses, i'll start a build thread. Figured i would place the schematic drawing there, that way i'll know it will work so others can use it for their jeeps or modify it to there liking.
Matthew Haver

 

I'm not sure I understand the benefits of the thru turbo design.
I'm no expert but I am a gearhead and have been in many different "schools" of tuning in one way or another.
If you could get a low rpm spooling turbo (I don't remember what the relationship is between turbo size and spooling) then you'd probably get the benefits of a turbo without the downfalls. But the turbo would be on mostly if I understand correctly. Also the more predictable turbo (lower rpm spooling speed) would probably be easier to conrtol in dicey situations.
I'm just chiming in....new member to the site today.