tgabriel

has anyone change the gear ratio to 3.73. and how did you fix the speedometer. what gears did you use in the trans.,because what they tell me is that with 2.83 gears are the same for 3.73 does not work....

Marlin

You are trying to change the gear of the trans right? If so see if you can find a donor trans and take it from that. if not find out what 700r4 you have, there were some differant versions, and see what yours will take. Plenty of trans parts online for that trans.

For the speedometer you need to change the gear in the trans tail housing. So may need some help to get the right one based on your rearend gear and tire size. I'm sure there is a chart out there or program to help. maybe someone here can help better.

nate99

There are vendors that sell speedometer gears. I think Bowtie Overdrives could probably help you out.

3.73's with a 700R4 in overdrive would be equivalent to having a 2.60 rear end with a TH350 in third (very nice for cruising). First gear in 700R4's is made for pulling stumps out of the ground with trucks, I think, with 3.73's it would be equivalent to having a 4.50 rear in first with a TH350.

http://www.700r4.com/faq/ratiocmp.shtml

I've thought a lot about swapping to an OD automatic, but now I'm leaning toward just spending the extra cash and going with a 5 speed manual.

gkull

The gear on the tranny side is easy to change. My 700 used a 4.11 rearend. I went to a local speedometer shop and bought the right colored gear.

RIO68

Put a 3.73 rear gear in mine--works good. First gear is low and changes real quick but as I understand I could put a shift kit in and change some of that but haven't so far. Got my colors, the gears are color coded, from BOW Tie OD's web site chart and got the gears originally from them but dealer is an option also once you know which ones you need.

tgabriel

so what colors did you get for drive gear and driven gear and have you check your odometer ??

mrvette

BTDT, the first thing you need to do is get a good GPS, and note the speeds indicated on your speedo, vs the truth, and divide it out to see the % change high or lo, either way, then add or subtract the teeth count off the existing DRIVEN gear....

so lets say for conversation sake, you have a indication of 70 on the freeway, but the GPS says 63 that's a 10% difference...

so you need subtract 10% of the teeth on the DRIVEN gear outta the side of the tranny,

so suppose it has 27 teeth on that gear, you put in a gear that has 24 teeth, and call it a day...

I got those tire size/ratio/overdrive ratio speeds crap shoved up but good some years ago....

another thing you find out, is that your speedo AND tach are NOT LINEAR in their response.....so at say 60 mph you can be dead nutz on with the GPS, but at 100 mph you are only doing a real 94 mph....

this has been proven pretty consistent over many cars....so much so I using a GPS for the motor home and hell with the speedo/odo

I know my '72 vette with o/drive is good for 78 mpn when speedo says 80, after that, it's all BS....

RIO68

Shaft gear is grey and drive gear is yellow-18/41 is the count. Looks good and matches RPM. Have not verified with GPS as to being accurate.

pricesgarage

@rio68 if u want to make it stay in gear longer first check proper tv adjustment if ok change the governer on the side of the tranny stock 700s shift at 4500 at wot if u get one from a 2. 8 f body they shift about 52-500 and 2.8 s10s shift closer to 6000

RIO68

Thanks for update info--

pricesgarage

no problem glad to help and thats a nice vette u have love red c3s