general tranny question

[USC87]

Posted a couple days ago in the trans tech but no responses, and I'm looking to move forward on it so I guess because it wasnt a high end thing I'm after maybe people didnt feel like bothering. Hoping for a better response here???

Bear with me, I have *very* limited trans knowledge. I'm redoing a car currently and getting to the trans phase of things. I'll be doing alot of driving when I'm done as this car will be both highway transportation and a cruiser for show nights.

Currently it has a th350 in it, and I'm thinking of going to a 200-4r. Its already got relatively high gears in the rear end as of right now (guess they call it highway gearing), and as it sits, I used to average in the 22-26mpg range on the highway. Seeing how I'm replacing the trans anyways, and with gas prices where they are headed, I'm hoping putting in the OD unit might bump it up?

I have heard what may just be misinformation that if you have high gearing in the rear end the OD might actually hurt your mileage, and drop your final drive ratio down so low it'd also be worse for the engine as well. If it helps this is a fairly low horsepower application this is a 109 block rwd g-body (NOT a SFI turbo car). Curious for any input on this at all? Like I said, not too knowledgeable on the subject. Thanks.

 

[MeanBuicks]

Unless you're getting a smoking deal on the 2004R, it'll take a bit of cash to buy one and get it installed. So even if there's a mileage improvement it'll take a while to pay for itself.

If you're planning on eventually changing the rear gears to something with more fun factor, put the 2004R in there now and if your car is chugging with the highway gears, just put it in third gear.

 

[LV GN]

the 2004r is almost a 100% bolt in for the 350. you will only need to change the kickdown cable. you could make good use of 4th gear at hiway speed's. but under that it will need to be back in 3rd. the only down side is cost.

 

[USC87]

The tranny thats in there now I've kept alive overall but is getting worn and nearing its last legs. It doesnt slip in gears yet, but it has had occasions where I've removed material from the pan when changing filters, fluid etc. Since I'm doing over the rest of the car anyways, and gearing it up for some cross country trips I'd rather take care of this before it breaks rather than after. Install I'll probably do myself, and I've seen prices on locally rebuilt stock-type spec units in the $5-600 range with no core.... granted, not BRF valvebodies or anything spectacular but its for a driver/cruiser not a racer. With the amount of driving I put in at times (occasionally 4-500 miles a day) if I pick up a 15-20% increase on highway mileage (4-5mpg?) It'd pay for itself inside a year. :biggrin:

So the key is going to be avoiding the OD when not on the highway.... doesnt sound too bad from the way things look right now.

 

[turbofish38]

I had an 84 Regal with the 4.1 and 200-4R with 2.73 gears. No problem cruising the highway,even at lower speeds.I never took it out of OD. I actually prefered this over the 2 barrel 231 with 350C and 2.41's that I replaced it with. I never did more than the high teens as far as MPG goes,with either one. Now I did run a 82 LeSabre wagon with a transplanted 455(about 300HP) with the 200-4R and 2.73's and it would lug down on the steeper grades. A swap to 3.08's cured that problem. MPG stayed the same too. You know if you look at todays newer cars you'll see a lot of them run an OD gear with a final drive in the high 2's,low 3 range. I think its going to depend more on what the weight of the car is and how much power the engine is really making.

One of my current dream projects is to take my 455 Regal and convert it back to a 3.8/4.1 V-6,only with the SFI system from a 86 Park Ave(same ECM as a TR). I'd like to put a T-5/T-56 in it but I would settle on using the 200-4R that is in it now. I'm trying to imagine if it will make enough low end torque to spin a set of 2.19's. I'd love to have a Regal that could get the low to mid 20's for MPG.