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My 1940 Chevy Restoration

T5 Transmission Page 
I decided that rather than do a ring and pinion swap on my 1955 1st series rear end, I would use an overdrive transmission instead. My first instinct was to find a 3 Speed overdrive transmission from a late fifties Chevy car. I had a similar transmission on a 1952 3/4 ton truck I owned a few years back. It was nice and allowed the truck to run near 60 miles an hour. My main concern with that transmission was the durability and replacement parts, especially the solenoid that operates the overdrive. 

I looked at a number of options including the Saginaw 4 speed, the MOPAR A833. Both have overdrive variants with Chevy bolt patterns. One problem! I did not want to give up the floor shifter and I certainly didn't want to go through the trouble of converting to column shifter. There are floor shifter kits that would work, but they all put the shifter very far back. Then I started noticing a lot of discussion around the Borg Warner T5. After following the information on that transmission and the fact that the S10 version had a top loader shifter that nearly replicates the original shifter position, I was sold. 

The picture to the left is the S10 T5 transmission I picked up for a little over $100.00. I thought all I would have to do is a simple rebuild. Not quite. Since getting this transmission I have learned some real lessons.

Number 1: Not all T5 transmissions are alike.
Number 2: The bell housing I was planning on using from the the 1940 does not have the standard Chevy bolt pattern and the later bell housing that does have the correct bolt pattern won't allow me to use the clutch and brake pedals from the 1940. Neither of these are going to be easy to fix.  

After buying this transmission I learned that I had actually bought the worst possible T5. This transmission is one of the earliest T5 transmissions used in S10s in 1982 and 1983. It is a normal T5 transmission, but it only has a .86 overdrive gear ratio. That means my top speed for the new truck would probably only improve to 75 mph with the 3.90 rear end. Not quite what I had in mind.

 
This transmission did have some qualities that were good for my project. It was in good shape, it had a mechanical speedometer drive, and the S10 shifter location. So I started doing some research into how I could improve the overdrive ratio for this "Non World Class" T5. I did a lot of reading on web pages. I found that the Jeep and Mustang world has a great presence on the web, but the camaro/firebird crowd does not.  The one web page/company that  helped me the most was Hanlon Motor Sports. They don't really do a lot with these older T5s, but the owner was willing to talk to me over the phone and point me in the right direction.

What he told me was basically the overdrive ratio is set by the input shaft and the cluster gear tooth counts. The early S10 and Jeep T5s used a 21 tooth input shaft and a 37 tooth cluster. This creates a 4.03 first gear ratio and with the standard 51 tooth 5th drive gear and 25 tooth driven gear, you get a .86 overdrive. Do the math and you'll see this is correct. The one option I had was to upgrade the entire transmission to a new cluster gear, new 2nd and new 3rd gear that produces a 2.95 first gear and then the 51/25 5th gear arrangement nets you a .63 overdrive ratio. Sweet!

This is the holy grail of T5 transmissions for Chevy truck applications. This gear arrangement was only used for 2 years on V8 firebirds and camaros. Racers love this transmission and the people at Hanlon Motor Sports said these transmission are getting like hens teeth. But if I wanted he could special order the parts needed. So I bought the T5 manual and the rebuild video as reference material and said I would study these first. The price for the new cluster and gears was about $450.00. A price I was willing to pay, but I needed to check stuff out first.

I'm glad I did because in the manual were some specification sheets for other T5s. The spec sheets gave me teeth counts for various gear arrangements. and applications that the various T5 transmission went into.

The big thing I discovered in these documents was that the 4.03 first gear transmission was pretty standard and that other 5th gear arrangements were used to improve the overdrive ratio on later transmissions. For one thing the same basic transmission used on V6 versions of the S10 had .72 overdrive ratios and that I could attain this gear ratio by replacing just the 2 5th gears with a 61/25 tooth set used in a couple of applications.

So armed with this information I went looking for a cheaper source of parts. In the process I bought another early S10 transmission to perform these two upgrades on. I hope to sell one to offset the cost of the other. 

The picture to the right is the guts of the first T5 and the entire second transmission I bought. The second box I got is a freshly rebuilt T5 I got on ebay. No one wants these early boxes and I got this one for $125.00. I have since taken the tailpiece off this box and it is a brand new box inside. I  think I got a great deal.

While searching for parts I came upon a source for some of the parts at Ariel Gear. I called and talked to a sales rep Ursula Welch. She was great and had all the information I needed. I ordered all the parts I need to do both transmissions for just a little more than what I would have paid for just the cluster and 2 gears other places. The 2.95 cluster, new 2nd and 3rd gear was around $290.00 and the new 61/25 tooth 5th gear set was around $ 150.00 dollars. I also bought some other parts I needed once I tore down the first transmission.

I sent the transmission case for the first T5 to the machine shop to get cleaned in their high pressure washer. I also spent a great deal of time with a wire brush attached to my cordless drill. It cleaned up pretty well.

This rebuild was actually very easy. I accomplished the entire job with tools I had on hand. Some pullers, punches, metric wrenches, and various ring pliers. The hardest part was keeping everything clean and in order. The service manual is a big help and the rebuild video from Hanlon Motor Sports was good, but it was for the World Class model of T5 transmissions. In many ways having two transmissions around was the best help and reference. Don't take both apart at once :)

In the end I have 2 transmissions that could be used in my truck. One is a close ratio box with a great overdrive, the other is a wide ratio box with a pretty good overdrive. The 2.95 first of the close ratio box very closely matches the 3.00 first of the original 3 speed found in these trucks. On the other hand the 4.03 first would be a better transmission if I was going to tow or pull anything with my truck. I will probably sell the 4.03 transmission once I have the 40' back on the road. 

One thing I found for the 4.03 transmission was a Jeep input shaft. The Jeep shaft is perfect because it retains the correct tooth count for the existing Cluster shaft and changes the input to a GM 10 spline input shaft. That allows you to use the OEM clutch. One of the problems with the T5 switch, The standard S-10 T5 comes with a 14 spline input and you have to find a clutch plate that will work. Not hard, put I paid $12.00 for this input on eBay. The 2.95 transmission uses a 21 spline input. I thought I was never going to find a clutch plate that would work with the flywheel I want to use. But I found that some late 70's Vegas used a 9 1/4 inch disk with 26 spline input. I bought one and it is perfect.  

 


Early  T5 Guts


Case is clean on the inside, but it was pretty bad on the outside


Here are the main components of the transmission, main shaft, input and cluster shaft.


This is what I replaced.


Here is the finished product.
I have put together a spread sheet I used to figure out the gear ratios. I have included the part numbers for the gears that let you make the changes I made to my transmissions. Call Ursula at Ariel Gear. She hooked me up with all this stuff. They don't even sell some of these items, but she researched the part numbers and found her supplier had them. I have also put the prices I paid for the gears, cluster and input. I don't believe these to be special prices, so you should be able to get them at a similar price. The deal of the lot is the cluster from Arial. $89 for this cluster is half I found it anywhere else.

The number in most of the columns are teeth counts.

Got any questions, email me.
Standard S-10 T5  Input Cluster Cluster Gear Ratio Notes
1st 21 37 14 32 4.027211  
Rev 21 37 15 32 3.75873  
2nd 21 37 23 31 2.374741  
3rd 21 37 34 29 1.502801   
4th 21 37 37 21 1  
5th 21 37 51 25 0.863679 Stock
Alternate 5th Gear Set 21 37 61 25 0.722092 Hanlon Motor Sports doc: "Uses w/t1352-18k & w/t1352-46E"
Ariel Gears: 13-52-080-067 61T $82.46
13-52-070-015 25T $74.67
             
New Close Ratio Box Input Cluster Cluster Gear   All info Ariel Gears:
Cluster / 13-52-077-060 / 89.26
Input / 13-52-085-010 / 45.34
1st 24 31 14 32 2.952381  
Rev 24 31 15 32 2.755556  
2nd 24 31 22 33 1.9375 2nd Gear / 13-52-080-131 / $44.80
3rd 24 31 29 30 1.336207 3rd Gear / 13-52-080-016 / $60.20
4th 24 31 31 24 1  
5th 24 31 51 25 0.63317 5th Gear / 13-52-080-065 / $85.19
I have added some detail shots to show some of the interesting items associated with this rebuild
This is the fine (26 spline) input shaft and the steel bearing retainer. Just the right setup for your oletruck. :) This is the B&M shifter I got off ebay. It is a short throw shifter that should make this feel pretty good while driving. I intend to buy or make a longer shifter to get that old truck look. The short throw should keep the length of the eventual shifter tolerable. I'll let you all know. Here is the solution to adding a T5 to older trucks like the 40'. This is a later (1947 - 195?) bell housing that Buffalo Enterprises has welded the appropriate brake and clutch pedal mounting onto. Easy to buy, probably easier to make. The bell housing came like it was dragged from a field. I wasn't too impressed with the condition when I got it. I ordered it from Jim Carter, but it was drop shipped from the supplier. It cleaned up ok though.  All I have to do now is drill the transmission to use the larger mounting bolts for this bell housing. 

Phase 1 of Rebuild
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